Avi Loeb Medium

(Image credit: Greg Wyatt)Since the instant that Galileo Galilei looked through his telescope at the sky, Astronomy was based on detecting light from the cosmos. The hot cosmic gas glowed early on, and we detected the radiation it emitted in the form of the cosmic microwave background. Afterwards, the cosmic gas condensed into galaxies — inside of which it fragmented into dense clouds that gave birth to luminous stars. When a star is born, the temperature at its core exceeds millions of degrees and so the fuel of hydrogen and helium starts to burn. Clusters of these nuclear fusion reactors are observed in the form of galaxies all the way to time when the Universe was just hundreds of millions of years old. This offers scientific details to the biblical story of genesis: “Let there be light!”, which I summarized in two textbooks here and here. (Image credit: Greg Wyatt)The debris disk of material left over from the formation process of the Sun included heavy elements that condensed in the disk midplane to make dust particles that stuck together to make rocks that coagulated to make rocky planets like Earth. There were many more Earth-size planets in the early Solar System and most of them were ejected through gravitational slingshot by Jupiter or other planets. The surviving planets are on stable orbits, but we know that shortly after the Earth formed — it likely collided with a Mars-size planet and shed some mass that gave birth to the Moon. The duration of a day on Earth was lengthened from about 4 hours early on to 24 hours today, as the Moon receded and stole the Earth’s rotation into its orbital angular momentum. Within 7.6 billion years, the Sun’s envelope might engulf the Earth-Moon system and cause the Moon to crash back on Earth as a result of its drag on the envelope’s material. (Image credit: Greg Wyatt)Everything around us keeps changing and as a young technological civilization, we need to learn how to survive in our turbulent cosmic neighborhood. Attending to lessons learned by advanced civilizations that survived for a longer period of time could guide us about the best strategy for our own survival. Observing the large scales of the cosmos endows us with a sense of cosmic modesty, but it also offers us a global perspective on the death of everything we get emotionally attached to. Over the cosmic timescale of billions of years, the best we can hope for is to rise to the level of an interstellar or perhaps an intergalactic civilization that started its life on a small rock near a common star but chose to be cosmologically ambitious despite all odds against its longevity. (Image credit: Greg Wyatt)It is unclear whether this is truly our destiny or just my wishful thinking. At any event, my hope is that by finding siblings from our family of intelligent civilizations who survived, we will be inspired to imitate them. Finding them will also provide us with an emotional connection to the Universe, far more powerful than the deterministic dynamics of matter and radiation described currently by our incomplete cosmological equations. Here’s hoping that the human spirit will ultimately prevail over all challenges imposed on it by our cosmic circumstances. *** In this essay, I featured four amazing watercolors from a series created by the celebrated artist, Greg Wyatt. These watercolors incorporate inspiring statements by Giordano Bruno, Cicero and Johannes Kepler. This is the sixth in a sequence of essays, where Greg and I collaborate on the interface between art and science. The first essay in this series, titled “Music of the Cosmic Spheres,” appeared here; the second essay, titled: “Cosmic Waterfalls in Spacetime Cliffs,” appeared here; the third titled “Missing Elements in the Cosmic Jigsaw Puzzle,” appeared here; the fourth essay, titled: “Why Do We Exist?”, appeared here; the fifth titled “Inspiration from the Stars”, appeared here; and the sixth titled “We Might Understand How the Cosmos Works Before We Understand How Life Works”, appeared here. ABOUT THE AUTHOR (Image Credit: Chris Michel, National Academy of Sciences, 2023)Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. The paperback edition of his new book, titled “Interstellar”, was published in August 2024. Professional website: https://lweb.cfa.harvard.edu/~loeb/ Social media: https://avi-loeb.medium.com/ https://www.youtube.com/@ProfessorAviLoeb https://open.spotify.com/show/1zhndXkvSY2b8FdjspFpCd https://x.com/ProfAviLoeb View the full article

A Sun-grazing comet, as observed by SOHO. (Image Credit: ESA/NASA/SOHO)The latest two puzzles about 3I/ATLAS stem from its large inferred size and mass (as reported here). First, its parent population cannot be supplied by the mass reservoir of planetary systems around old metal-poor stars (as I argued here). Second — its mass of a billion metric tons is 5 orders of magnitude larger than the final mass of 1I/`Oumuamua, implying that we should have discovered a hundred thousand interstellar objects on the mass scale of 1I/`Oumuamua before seeing one giant object like 3I/ATLAS (as I argued here). Altogether, the full list of 22 anomalies for 3I/ATLAS (summarized here) is particularly timely, as the mysterious object comes closest to Jupiter today on its way out of the Solar System. If the passage near Jupiter will not reveal any new insight on 3I/ATLAS, we will be left with many questions about its nature and origin. Can we hope to learn more about future interstellar visitors? The best way to examine visitors to our cosmic back yard is to interrogate them under extreme heat. This opportunity is realized for Sun-grazing trajectories. In 2019, I co-authored a paper (published here) with my then-postdoc, John Forbes, which explored the statistics of close encounters between interstellar objects and the Sun. Objects similar to 1I/`Oumuamua collide with the Sun once every 30 years. A Sun-grazing passage would vaporize any solid surface, unraveling the composition and structure of the object’s interior by detailed observations from the Inouye Solar Telescope (DKIST) in Hawaii or the Solar and Heliospheric Observatory (SOHO) in space. On April 4, 2026, we will have a unique opportunity to witness a rare Sun-grazing encounter by the large object, C/2026 A1 (MAPS), which was discovered on January 13, 2026 from the AMACS1 Observatory in Chile. The object will pass within 161,000 kilometers (23.1% of the Solar radius) from the surface of the Sun. From the vantage point of Earth, the object will enter Solar conjunction behind the Sun on April 4, 2026 at 13:19 UTC and appear in front of the Sun at 15:34 UTC, in both case being separated by 0.04 degrees from the center of the Sun. The unusual trajectory of C/2026 A1 (MAPS) suggests that it is a member of a yet unknown group of comets that are bound gravitationally to the Sun. Could it be a fragment that broke off 3I/ATLAS and was launched into a bound orbit around the Sun? Probably no, because its inferred diameter of somewhat less than 2.4 kilometers is comparable to that of 3I/ATLAS, and the orbital inclination of C/2026 A1 (MAPS) is 144.5 degrees, about 30.6 degrees away from the 175.1 degrees inclination for 3I/ATLAS. C/2026 A1 (MAPS) will pass through the solar corona and reach perihelion with a peak speed of 557 kilometers per second (0.2% of the speed of light) on 4 April 2026 at 14:21 UTC. At that time, it will be separated from the center of the Sun by 0.57% of the Earth-Sun separation. It will then make closest approach to Earth on 5 April 2026 at 23:56 UTC when it will be at a distance of 143.8 million kilometers (96.1% of the Sun’s distance) from Earth. Observing the fireworks as this object burns up and breaks close to the Sun will reveal new details about its composition and material strength. Before my morning jog at sunrise today, I received the following uplifting email about C/2026 A1 (MAPS): “Dear Professor Loeb, I want to truly thank you for your intellectual courage. In a field that too often punishes curiosity, you have chosen the path of truth over comfort and you have had a profound impact on our children. We have been watching you refuse to dismiss the unexplained and face backlash from a stagnant scientific community. This rare quality has given children around the world the conviction that pursuing truth is worth the cost of facing criticism or being unpopular. You are truly one of the great scientists of our time and one can only hope that the censorship and elitism we see in the science community specifically and society as a whole can be diminished. After seeing the myriad anomalies with 3i ATLAS, we have been applying this same curiosity to other objects passing through our celestial neighborhood. There has been relatively little coverage of another unique guest- C/2026 A1 (MAPS). Headlines have been quick to file it under “Kreutz sungrazer” and move on but the data resists that tidy label. Its orbital period of nearly 1,900 years is at least twice as long as any other Kreutz members. It was detected 81 days before perihelion at a distance of greater than 2 AU!! That’s significantly farther from the Sun than any previously known Kreutz comet and suggests unusual size or extraordinary activity. And now its brightness is running dramatically ahead of predictions, currently around magnitude 9.9, with no satisfying conventional explanation for why it is brightening so aggressively at this stage. These anomalies raise questions I would love your perspective on: 1. Given that MAPS appears orbitally inconsistent with the Kreutz family of comets, should it be treated as an unclassified object until better data is available? 2. Could the runaway brightening indicate something unusual about the composition or structure of the nucleus that standard cometary models don’t account for? 3. Can this possibly survive its close encounter with our sun and put on the greatest show of the millennium? You have shown that the most important questions are often the ones we are most reluctant to ask. My family is grateful for that example. With deep respect and love, Chris and Stephanie Francois and our kids Joshua, Nicholas, Savannah, Thomas, Enzo and Sophia” Shortly afterwards, I had received the following email from the poet Alan Wagstaff in New Zealand: “Dear Dr Loeb, Here’s my response to your oft-mentioned ideas about confirmation bias in science. It’s a formal sonnet. I hope it communicates. It’s a complex idea and has a slight humorous edge. Best wishes Alan ‘A man sees what he wants to see…’ * I’m nonplussed since you visited my home, in part, because you dropped in — unannounced. It seems so weird: you never said ‘shalom’, ‘aloha’, or ‘hello’. Instead, you bounced and squeaked, high pitched, and droned, bee-like, off-key. You hovered in mid-air and softly whined. “No chance,” I mused, “that you could be E.T!” For certain, you’re not extra-humankind, since mainstream physics locks us in a vault, which shuts-out off-world creatures’ whims. Your purple tendrils, signing us to ‘halt’, in truth were plant fronds I mistook for limbs. Since you’re not human from some unknown tribe. You must be Terra-cryptid, I decide. Alan Wagstaff * from ‘The Boxer’ Paul Simon” (Image credit: Alan Wagstaff)ABOUT THE AUTHOR (Image Credit: Chris Michel, National Academy of Sciences, 2023)Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. The paperback edition of his new book, titled “Interstellar”, was published in August 2024. Professional website: https://lweb.cfa.harvard.edu/~loeb/ Social media: https://avi-loeb.medium.com/ https://www.youtube.com/@ProfessorAviLoeb https://open.spotify.com/show/1zhndXkvSY2b8FdjspFpCd https://x.com/ProfAviLoeb View the full article

The Mass of 3I/ATLAS is About a Billion Metric Tons, at Least a Hundred Thousand Times That of 1I/`OumuamuaObservational data on the evolution of the mass loss rate of 3I/ATLAS dM/dt in various gasses: H2O (blue), OH (orange) and CO2 (green). The colored dashed-lines show various models for the mass loss rate. The solid pink and red curves display two preferred models to describe the combined total emission rate from water and carbon dioxide. The gray dotted line illustrates a previous model, favored in interpreting the rocket effect based on Hubble Space Telescope data (as reported here). (Image Credit: V. Thoss, A. Loeb and A. Burkert 2026)A new paper (accessible here) that I just co-authored with the brilliant Valentin Thoss and Andi Burkert from the University Observatory Munich, provides the best assessment to date of the mass of the mysterious interstellar object 3I/ATLAS. As I discussed here on October 31, 2025, the rocket equation can be used to evaluate the non-gravitational force acting on 3I/ATLAS. The mass of 3I/ATLAS, M, times its non-gravitational acceleration, A, should be equal to the excess mass loss in a preferred direction, ζdM/dt, times the ejection velocity of the outflowing material, V, M×A = (ζdM/dt) × V . This provides a way to measure the mass 3I/ATLAS. By measuring the acceleration A and the mass-loss rate dM/dt and by modeling the velocity V, it is possible to derive the mass M of 3I/ATLAS for a reasonable value of the outflow asymmetry-parameter ζ ~0.5. The new paper uses all available observational data on the evolution of the production rate of gas and dust and the brightening of 3I/ATLAS during the months surrounding its close approach to the Sun on October 29, 2025. The outgassing from the nucleus has led to a detectable non-gravitational acceleration. Our analysis combines models for the mass loss rate of water (H2O) and carbon dioxide (CO2) to derive the non-gravitational force and estimate the mass and size of 3I/ATLAS. In addition, we take into account a conservative constraint on the nucleus size from the active surface required for sublimation. If the mass loss is dominated by the sublimation of CO2, then the nucleus diameter is 0.84 kilometers, assuming a mass density of 0.5 grams per cubic centimeter and an asymmetry-parameter ζ ~0.5. Strong water sublimation of up to 10 metric tons per second from the surface is ruled out, as the required cometary surface area is incompatible with the rocket effect. A more conservative model of water production suggests a nucleus radius of 0.74 kilometer. In this case, a lower than usual cometary density or larger outgassing velocity could make the nucleus size estimate compatible with the lower bound of Hubble Space Telescope data of 2.6 (± 0.4) kilometers (as reported here). Our analysis adopted three parameterizations: a purely CO2-driven sublimation which scales inversely with the square of the distance to the Sun, and two models accounting for the contribution from water sublimation. These two models were fitted to the highest (model A) and lowest (model B) reported production rates, encompassing the range of uncertainty. By combining these models with data on the motion of 3I/ATLAS in the sky, we have estimated its mass and size. There is a subtle statistical preference towards the CO2 model with an inverse-square scaling, which becomes pronounced when we only include the data from large telescopes and interplanetary spacecraft. Despite systematic uncertainties, the magnitude of the non-gravitational acceleration can be estimated quite robustly. The derived mass of 3I/ATLAS is (M/ζ)= 0.3 × 10^{12} kilograms for a CO2-only model, where ζ is the outgassing asymmetry factor. Including the contribution from water sublimation, we obtain (M/ζ)= 1.7 × 10^{12} kilograms and (M/ζ) = 6.4 × 10^{12} kilograms for the low and high limit of water sublimation from the nucleus. All in all, the mass of 3I/ATLAS is of order a billion metric tons! Assuming a bulk density of 0.5 gram per cubic centimeter and ζ = 0.5, we estimate the diameter of 3I/ATLAS to be 0.84 kilometers for the CO2-driven sublimation, and 1.48 kilometers or 2.3 kilometers for the low (model B) or high (model A) limit of water sublimation. Minimum radius (half-diameter) of the nucleus of 3I/ATLAS, required to sustain the observed production rate of gas with the entire surface being active. The solid lines correspond to various outgassing models and the dotted lines are the corresponding lower limits for the radius of 3I/ATLAS based on its non-gravitational acceleration. (Image Credit: V. Thoss, A. Loeb and A. Burkert 2026)We derive an additional constraint on the size of 3I/ATLAS by considering the surface required to sustain the sublimation. Under the most conservative assumptions, this leads to a strong tension for the model with high values of water production, requiring a diameter larger than 3 kilometers compared to the maximum value of 2.3 kilometers based on the corresponding non-gravitational acceleration. The high sublimation rate would therefore require a nucleus size that is too large to be compatible with the non-gravitational effect, even under extreme assumptions. This rules out model A and the corresponding mass and nucleus size, while the more conservative model B with lower levels of water production produces a mild tension, which could be alleviated by a lower bulk density or higher ejection velocity. This also implies that the sublimation of water (H2O) from the surface of 3I/ATLAS likely does not significantly exceed that from carbon dioxide (CO2). On the other hand, the bounds for a model which only includes CO2-sublimation is compatible with the non-gravitational estimates of the nucleus size. The constraints from the active fraction suggest that the rocket effect of 3I/ATLAS might be dominated by CO2 sublimation throughout the orbit, with negligible contribution from water production. In this case the nucleus has an effective diameter of 0.8 kilometers, inconsistently with the Hubble data analysis that provided 2.6 (± 0.4) kilometers. Only if the production rates of CO2 have been underestimated by about an order of magnitude, could the two estimates be reconciled. If on the other hand water sublimation does contribute to the rocket effect of 3I/ATLAS, then the nucleus size would be larger. In this case, a lower than usual comet density together with larger gas velocities and collimation of the outflow could potentially push the estimated diameter as high as 2.2 kilometers, resolving the tension with the Hubble estimate and the required active fraction. Additional data on the production rates of water and carbon dioxide would help to narrow down the range of possibilities and improve estimates of the mass and size of 3I/ATLAS. But irrespective of the uncertainties, one conclusion is beyond any reasonable doubt: the third interstellar object 3I/ATLAS is at least 5 orders of magnitude more massive than the first interstellar object 1I/`Oumuamua — whose final mass was estimated to be of order 10⁷ kilograms here and here, assuming a natural origin for it as a hydrogen or a nitrogen iceberg without a visible cometary tail. Based on the statistics of asteroids and comet nuclei of various sizes in the Solar System, we should have detected at least a hundred thousand 1I/`Oumuamua-mass objects before discovering a single interstellar object with the mass of 3I/ATLAS. Does this discrepancy mean that one or both of these two mysterious interstellar objects is not natural in origin? ABOUT THE AUTHOR (Image Credit: Chris Michel, National Academy of Sciences, 2023)Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. The paperback edition of his new book, titled “Interstellar”, was published in August 2024. Professional website: https://lweb.cfa.harvard.edu/~loeb/ Social media: https://avi-loeb.medium.com/ https://www.youtube.com/@ProfessorAviLoeb https://open.spotify.com/show/1zhndXkvSY2b8FdjspFpCd https://x.com/ProfAviLoeb View the full article

An artist’s illustration of a magnetar — a rotating neutron star with a magnetic field of up to a quadrillion Gauss (a hundred billion Tesla). (Image Credit: Quanta Magazine)What would be the flagship signature of a very advanced, ambitious civilization? One possibility is the technology to propel a spacecraft the size of New-York City along with its population of ten million residents to the speed of light over a period of about a year. This requires an average acceleration of 1 gee, similar to the surface gravity of Earth. The acceleration phase would feel like living on the surface of Earth, as according to Albert Einstein’s theory of General Relativity — there is no fundamental difference between an artificially-induced acceleration and gravitational acceleration. Keep in mind that an observer within a free-falling elevator feels no gravity whatsoever. How can we drive roughly a million tons to the speed of light in one year? A simple technology that can accomplish that challenge is light sails. An Earth-size membrane, illuminated by a radio transmitter that harvests the total power of starlight on the surface of a habitable Earth-like planet, could carry this massive payload up to the speed of light over a period of a year. The optimal radio frequency to keep the light beam focused on the sail during the acceleration period is of order 1 gigahertz. Given the motion of this narrow radio beam in our sky, this system would generate a fast radio burst (FRB) that lasts a thousandth of a second (millisecond) for a launch system at a cosmological distance of the order of billions of light years. The brightness of the FRB would be roughly about 1 Jansky. As it turns out, several thousand FRBs with millisecond duration and this brightness were detected at cosmological distances. Could some of them be related to advanced technological civilizations? I raised this possibility in a paper that I published here in March 2017, with my then-postdoc, Manasvi Lingam. The publication date was seven months before the first interstellar object 1I/`Oumuamua was discovered, exhibiting a flat geometry as well as a non-gravitational acceleration that declines inversely with the square of its distance from the Sun, as expected from a light-sail. I therefore suggested that `I/`Oumuamua might be a light-sail (here) or a broken piece of a thin Dyson sphere (here) . The light-sail conjecture for FRBs was sidelined and replaced by the popular hypothesis that the sources of these bright radio transients are relatives of fainter radio sources, called pulsars, which are routinely discovered in the Milky-Way galaxy. Pulsars are rotating neutron stars, relic from the collapse of the cores of stars more massive than 8 solar masses, after they consume their nuclear fuel. A neutron star typically packs 1.4 solar masses within a radius of 12 kilometers, about half the length of Manhattan Island. If its rotation axis is misaligned with its magnetic axis which beams radio waves, it appears as a pulsating lighthouse as the radio beam crosses our line-of-sight, hence the name pulsar. As of a result of their energy loss, pulsars spin down with the product of the spin-down rate scaling as the square of the magnetic field strength. Typical pulsars display a magnetic field of up to a trillion (10^{12}) Gauss (equivalent to a hundred million Tesla), but some rare neutron stars show evidence for a magnetic field which is up to a thousand times larger. These are called magnetars. The popular view is that FRBs originate from the powerful radio beams emitted by magnetars and none are related to alien civilization. Pulsars are born when the core of a massive star bounces, leading to the ejection of the envelope of the star. The energy released in the bounce is comparable to the gravitational binding energy of the relic neutron star, and typically 99% of it is carried by neutrinos — weakly interacting particles that escape relatively easily from the collapsed core. The remaining 1% drives an explosion — called a supernova — which disperses the debris of the stellar envelope into the surrounding interstellar medium and enriches it with the heavy elements that were cooked inside nuclear furnace of the progenitor star. Most of the weight of our body comes from oxygen and carbon that were produced by nearby supernovae. Some supernovae appears to be an order of magnitude more luminous than typical supernovae, and are therefore labeled as superluminous supernova. A new paper that was just published in Nature magazine here, reports the discovery of a periodic modulation in the lightcurve of a superluminous supernova. The modulation is naturally explained by the precession of an accretion disk around a newly-formed magnetar. The measured spin period of 4.2 (± 0.2) millisecond and the inferred spindown rate are consistent with a magnetic field of a hundred trillion (10^{14}) Gauss (equivalent to ten billion Tesla). This constitutes the first discovery of the birth of a magnetar. We now know how some magnetars can be born with the necessary spin period and magnetic field to produce FRBs. But are all FRBs associated with young magnetars? Certainly not. Massive stars are short lived and so we expect magnetars to be born in young, star forming environments. However, we know that a subset of FRBs — represented for example by FRB 20240209A (reported here), reside in old, quiescent elliptical galaxies. This finding challenges the assumption that FRBs only originate from magnetars formed in young, star-forming region. Science is fun when treated as a learning experience. It is based on the humility to learn, not the arrogance of expertise. *** Before my morning jog at sunrise, I received the following uplifting message: “Dear Professor Loeb, I have been following your work for some time. Even as a non-scientist, I feel deeply moved and inspired by what I sense you are trying to do — both within your scientific vision and in the invitation that you extend to those willing to listen. In your recent talks I sensed something very sincere: an open call to curiosity, to wonder, and to the courage of asking questions before we have answers. That invitation inspired the small visual poem I am sending you. Please accept it simply as a humble gesture of participation in what I perceive as your call to a science that remains profoundly human. For context, I am a poet. I recently published a book written in dialogue with an artificial intelligence — not as a tool, but as a respectful collaboration with what one might almost call an alien form of intelligence. The image accompanying the poem was generated in that same spirit by the AI that collaborated with me. Thank you for the curiosity and intellectual courage you bring to the public conversation about science. Warm regards, Andrea Fassone In the House of θαυμάζειν … it moves still and out of sync yet in unison through singularity that feeling is too little of measure and suspension memore beyond time to nothing before nor after it aches that something behind the stone cast and me who watches… AF — IN MEDIA VIA” ABOUT THE AUTHOR (Image Credit: Chris Michel, National Academy of Sciences, 2023)Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. The paperback edition of his new book, titled “Interstellar”, was published in August 2024. Professional website: https://lweb.cfa.harvard.edu/~loeb/ Social media: https://avi-loeb.medium.com/ https://www.youtube.com/@ProfessorAviLoeb https://open.spotify.com/show/1zhndXkvSY2b8FdjspFpCd https://x.com/ProfAviLoeb View the full article

The latest image of a fading 3I/ATLAS on March 11, 2026 at 19:22:54 UTC, based on ten 120 second, R-band exposures with a 25-centimeter telescope and an angular resolution of 1.38 arcseconds per pixel. Jupiter is outside the field of view. (Image Credit: Toni Scarmato)The interstellar object 3I/ATLAS is fading away. It will get closest to Jupiter on March 16, 2026 and then head out of the Solar System in a nearly symmetric fashion to the way it came in. I say `nearly symmetric’ because 3I/ATLAS exhibited a small non-gravitational acceleration, owing to a remarkable system of jets. The passage of 3I/ATLAS on a retrograde orbit within 5 degrees of the ecliptic plane provided an ideal opportunity for a spacecraft to intercept its path, take a close-up photograph, collect a sample from it, or even plant a capsule full of technology or life-as-we-know-it in its belly and hitchhike it to interstellar space at 60 kilometers per second — twice as fast as our fastest rockets. We missed all of this rare opportunity. We should aim to do better in our next encounter with a mysterious interstellar object. But given the rare properties of 3I/ATLAS, it is unclear whether we will be given such an opportunity any time soon. So long, our interstellar friend. The nature of 3I/ATLAS is intriguing because of the following 22 anomalies: Mass Budget Discrepancy: 1. The inferred nucleus diameter of 2.6 kilometers and number density of its parent population (assuming a natural comet) exceed the mass reservoir of planetary disks around low-metallicity stars (as inferred here and here) by orders of magnitude. More details are available here. Geometric Rarities: 2. The retrograde trajectory of 3I/ATLAS is aligned to within 5 degrees with the orbital plane of the planets around the Sun, with a probability of 0.2% (as discussed here). The Milky-Way disk is misaligned with the ecliptic plane by about 60 degrees. This suggests that the trajectory of 3I/ATLAS may have been planned. 3. The arrival time of 3I/ATLAS was fine-tuned to bring it to minimum distances of 29 and 54 million kilometers from Mars and Jupiter, respectively, and be unobservable from Earth at perihelion (as discussed here). 4. The perijove distance of 3I/ATLAS during its encounter with Jupiter on March 16, 2026 is 53.6 million kilometers, is very close to Jupiter’s Hill radius, 53.5 million kilometers (as discussed here). 5. Analysis of the Hubble Space Telescope image of 3I/ATLAS from July 21, 2025 (as discussed here) suggests that the anti-tail before perihelion must have been in the form of a collimated jet towards the Sun that is about ten times longer than it is wide. This is similar to the collimation observed in post-perihelion images out to several hundred thousand kilometers. No known comet exhibited a physical sunward jet of this length that is not a perspective effect. For a technological object, a beam of particles might be used to block the solar wind from impacting the nucleus surface at a relative speed of order 500 kilometers per second. In addition, the veil of dust around 3I/ATLAS is just of the right column needed to block sunlight from hitting the nucleus surface (as discussed here). 6. At large distances, the initial rotation axis of 3I/ATLAS was aligned to within 8 degrees with the sunward direction when it entered the solar system (as reported here). The probability for that is 0.5%. 7. The observed wobble of the pre-perihelion anti-tail jet in the direction of the Sun (as reported here during July and August 2025) requires the base of the jet to be within 8 degrees from the sun-facing pole, with a probability of 0.5%. 8. The existence of a prominent anti-tail jet towards the Sun on the way of 3I/ATLAS out of the solar system requires a similar coincidence near the opposite pole of the rotation axis (as discussed here). The fact that a collimated jet appears as the sunward anti-tail both before and after perihelion (while reversing direction at perihelion relative to the direction of motion), has a tiny probability of occurring at random, equal to the square of 0.5% or 0.000025. 9. The launch base of the post-perihelion anti-tail jet resided on the nightside of 3I/ATLAS before perihelion and the base of the pre-perihelion anti-tail jet is now on the nightside of 3I/ATLAS after perihelion. For these bases to be active only when facing the Sun, they must be well insulated on the nightside for a period longer than several months. Heat naturally flows by conduction throughout the body of a natural comet, making this insulation requirement difficult to satisfy. 10. The gravitational deflection of 3I/ATLAS by 16 degrees at perihelion (as discussed here), is exactly twice the opening angle of the anti-tail before perihelion. This coincidence allows the wobbling jet around the rotation axis to generate an anti-tail in the direction of the Sun before perihelion and a counter jet on the opposite pole after perihelion, with a jet opening angle of 8 degrees on both poles. 11. On January 22, 2026, 3I/ATLAS aligned with the Sun-Earth axis to within an extraordinarily small angle of 0.69 degrees (as discussed here). At that time its anti-tail pointed at Earth. Possible techno-signatures: 12. 3I/ATLAS arrived from a direction coincident with the radio “Wow! Signal” to within 9 degrees, with a probability of 0.6% (as discussed here). 13. Processing of 40 Hubble Space Telescope Images from November 2025 to February 2026 by the Larson-Sekanina filter — which removes the circularly-symmetric glow round the nucleus, reveals a system of three mini-jets which are symmetrically separated by 120 degrees from each other (as discussed here and here). Are these symmetric jets coming the sublimation of pockets of ice on a rock or technological thrusters? 14. The non-gravitational acceleration of 3I/ATLAS was not directed away from the Sun but had a substantial sideways component (as discussed here). Composition Anomalies: 15. Before perihelion, the gas plume surrounding 3I/ATLAS contained much more nickel than iron, as found in industrially-produced nickel alloys, and a nickel to cyanide ratio that is orders of magnitude larger than for thousands of known comets, including 2I/Borisov (as reported here). 16. The anti-tail penetrated hundreds of thousands of kilometers through the solar wind and the solar radiation. In order not to be stopped, the dust particles must be much larger than common sub-micron particles of interstellar dust (as discussed here). However, if the particles are bigger than a millimeter, then they must carry an untenable amount of mass in order to account for 99% of the scattered sunlight around 3I/ATLAS, as observed in the Hubble images. 17. Data from the SPHEREx space observatory indicated the existence of icy fragments around 3I/ATLAS before perihelion (as reported here in August 2025). However, the spectral signature of ice disappeared in the SPHEREx data after perihelion, taken during December 2025 (as reported here), when abundant organic molecules in gas phase, such as CH3OH, H2CO, CH4, and C2H6, were discovered, along with an enhancement by a factor of ~20 in the water production rate. To survive cosmic-ray bombardment along an interstellar journey that lasted billions of years, these organic molecules must have been buried under a thick layer of material, at least 10-meters in depth. 18. The isotope abundances of hydrogen (D/H) and carbon (12C/13C) are markedly different from Solar System comets and suggest an rare birth environment with a freezing temperature of less than 30 degrees Kelvin and a low metallicity (as discussed here). Possible Bio-Signature: 19. The volatility of methane (CH4) is between that of carbon dioxide (CO2) and carbon monoxide (CO), yet methane was detected in the gas plume around 3I/ATLAS only after perihelion, while CO2 and CO were detected long before perihelion. This puzzle (discussed here) suggest a strange layered composition of the nucleus. Methane and other organic molecules are known bio-markers. Does 3I/ATLAS carry life on it (as discussed here)? Unusually High Mass, Speed, Polarization and Perihelion Brightening: 20. The nucleus of 3I/ATLAS is more massive than 1I/`Oumuamua and 2I/Borisov, while moving faster than both (as discussed here and here). 21. 3I/ATLAS shows extreme negative polarization, unprecedented for all known comets, including 2I/Borisov (as discussed here and here). This unusual polarization may be related to its unusual anti-tail. 22. Near perihelion, 3I/ATLAS brightened faster than any known comet and was bluer than the Sun (as discussed here). *** Given these 22 anomalies, the nature of 3I/ATLAS remains mysterious. Even if 3I/ATLAS is a natural comet, there are some fundamental aspects of its physical properties and birth environment that we do not understand. Many of the above anomalies, like its near alignment with ecliptic plane or the “Wow! Signal”, will be treated by comet experts as chance coincidences. But others, like the mass budget discrepancy, the prominent anti-tail jet or the symmetric jet structure must be explained by physical models. It is easy to insist that 3I/ATLAS is a natural comet while ignoring these anomalies. However, it is the responsibility of scientists and NASA officials to acknowledge the existence of unexplained puzzles rather than display the arrogance of expertise while ignoring them. When 3I/ATLAS was discovered in July 2025, I gave it a rank of 4 on the Loeb Classification scale of interstellar objects (quantified here, here and here), where 0 means a natural comet and 10 means alien technology that poses a major threat to humanity. Given all that we have learned so far and assuming that nothing unusual will occur near Jupiter, I regard 3I/ATLAS — which showed cometary activity, to be only slightly less anomalous than 1I/`Oumuamua — which had no visible cometary activity and a larger non-gravitational acceleration. Science is fun as long as we treat life as a learning experience. ABOUT THE AUTHOR (Image Credit: Chris Michel, National Academy of Sciences, 2023)Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. The paperback edition of his new book, titled “Interstellar”, was published in August 2024. Professional website: https://lweb.cfa.harvard.edu/~loeb/ Social media: https://avi-loeb.medium.com/ https://www.youtube.com/@ProfessorAviLoeb https://open.spotify.com/show/1zhndXkvSY2b8FdjspFpCd https://x.com/ProfAviLoeb View the full article

A Hubble Space Telescope image of 3I/ATLAS (Image Credit: NASA, ESA, STScI, D. Jewitt (UCLA), M.-T. Hui (Shanghai Astronomical Observatory))In a new paper (accessible here), I show that the recently inferred radius and interstellar number density of 3I/ATLAS-like objects, imply a local mass density that is larger by orders of magnitude than the available reservoir of heavy elements locked in low metallicity stars. This association was suggested by recent isotope abundance measurements. Either the inferred radius or number density are overestimated or the association with metal-poor stars is incorrect. The interstellar object 3I/ATLAS offers new insights into the mass reservoir of planetary systems across the Milky-Way galaxy. The latest data from the Hubble Space Telescope (reported here), was used to derive a nucleus radius of R_n = 1.3 ± 0.2 km and an interstellar number density of n ∼ 7 × 10^{−3} au^{−3} (where au is the Earth-Sun separation). For a typical nucleus density of ρ_n ≈ 0.5 g/cm^3, the inferred radius implies a nucleus mass of m_n ≈ (4π[R_n]^3ρ_n/3) = 4.6×10^{15} g. Hence, the local interstellar mass density of the population of 3I/ATLAS-like objects is, ρ_{3I} ≈n×m_n =10^{−26} g/cm^3 Two recent papers (posted here and here) reported anomalous isotope abundances in the material that makes 3I/ATLAS. Based on JWST observations, Cordiner et al. (2026) had found an isotope composition unlike any Solar System body. The water in 3I/ATLAS is enriched in deuterium at a level of D/H = (0.95 ± 0.06) percent, which is an order of magnitude higher than in known comets, suggesting a metal-poor origin. In addition, the 12C/13C isotope ratios (141–191 for CO2 and 123–172 for CO) exceeds typical values found in the Solar System, as well as in nearby proto-planetary disks. Chemical evolution models imply that the carbon isotopic composition originated 10–12 billion years ago. A similar conclusion was reached by Opitom et al. (2026), who reported measurements of carbon and nitrogen isotope ratios in 3I/ATLAS from observations of the cyanide (CN) molecule by the VLT. This data suggests a 12C/13C ratio of 147 (+87/−40) and a 14N/15N ratio of 343(+454/-124), more than twice above the value of ∼ 150 usually measured for Solar System comets. Below, I show that a low-metallicity origin for 3I/ATLAS generates untenable tension with the inferred mass budget of the 3I/ATLAS population of interstellar objects. The Galactic orbit of 3I/ATLAS suggest a likely origin in the disk of the Milky-Way galaxy. The composition of the coma of 3I/ATLAS in terms of carbon, oxygen and nitrogen — based molecules, implies that most of its mass is associated with heavy elements. For reference, the Galactic mass density of stars in the neighborhood of the Sun is, ρ_⋆ ≈ 0.04M_⊙ pc^{−3} = 2.7 × 10^{−24} g/cm^3 Only a tenth of all stars in the Milky-Ways disk have metallicities below a tenth of the solar value. Considering those metal-poor stars as the suggested source population of 3I/ATLAS and adopting their metal mass fraction to be ∼ 2 × 10−3, we find the corresponding local mass density of heavy elements in them to be, ρ_z ≈2×10^{−3}×0.1×ρ_⋆ =5.4×10^{−28} g/cm^3 Since ρ_z ∼ 0.05ρ_{3I}, we conclude that the total mass density of heavy elements locked in low-metallicity stars is more than an order of magnitude below the required mass density in interstellar objects like 3I/ATLAS. Planetary systems — which serve as the natural birth sites of interstellar objects — originate from debris disks that contain at least ten times less mass than the host star. In addition, one expects a mass spectrum of ejected inter- stellar objects to contain at least ten times more mass in objects with masses that are orders of magnitude different from that of 3I/ATLAS. When these additional factors are included, we find that low-metallicity stars miss the required mass budget by at least 3 orders of magnitude. They cannot account for the interstellar population of 3I/ATLAS-like objects unless they are capable of ejecting to interstellar space more than a thousand times the heavy-element content of their planetary disks. In conclusion, either the inferred radius or number density of the population of 3I/ATLAS-like objects are overestimated or their association with metal-poor stars is incorrect. ABOUT THE AUTHOR (Image Credit: Chris Michel, National Academy of Sciences, 2023)Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. The paperback edition of his new book, titled “Interstellar”, was published in August 2024. Professional website: https://lweb.cfa.harvard.edu/~loeb/ Social media: https://avi-loeb.medium.com/ https://www.youtube.com/@ProfessorAviLoeb https://open.spotify.com/show/1zhndXkvSY2b8FdjspFpCd https://x.com/ProfAviLoeb View the full article

Spectral-line maps for 3I/ATLAS, observed with the Webb telescope’s NIRSpec: Top panel (a): water (H2O) at 2.7 micrometers; middle panel (b): carbon dioxide (CO2) at 4.3 micrometers; and bottom panel ©: carbon monoxide (CO) at 4.7 micrometers. Inset panels (upper right) show the respective line spectra. Lower left corner shows the direction of the Sun and nucleus velocity (v). (Image Credit: M. Cordiner et al. 2026)The chemical interactions of atoms are dictated by the number of electrons they possess. The electron cloud around the atomic nucleus balances the charge of the nucleus, which is proportional to the number of protons in it. Since the charge of the electron equals that of the proton, the number of electrons in a neutral atom equals the number of protons and dictate the chemical behavior of the atom. However, atomic nuclei can also contain neutrons which are electrically neutral. Stable nuclei often have comparable number of protons and neutrons but they can have variants with a surplus or a deficit of a few neutrons. Isotopes are atoms with nuclei that have identical number of protons but different number of neutrons. The relative abundance of different isotopes of the same element depends on local production channels, such as exploding stars of different masses, the distance to the nearest historic merger of neutron stars or bombardment of nuclei by energetic cosmic-rays. The Solar System formed out of a cloud of gas that was uniformly enriched by the same local processes. As a result of this specific origin, the isotopes found on Earth, other Solar System planets, asteroids or comets, have similar isotope ratios and serve as fingerprints of Solar System materials. Whereas the relative abundances of elements can be modified by chemical reactions which select some of them relative to others, the isotopes abundance ratio of a specific element can only be modified by nuclear processes which require temperatures in excess of ten million degrees, not found on planets, asteroids or comets. Two new papers (posted here and here) report today about anomalous isotope abundances in the material that makes the interstellar object 3I/ATLAS. The first paper, led by Martin Cordiner, reports that isotope measurements of 3I/ATLAS with the Webb telescope reveal a composition unlike any Solar System body. The water in 3I/ATLAS is enriched in deuterium — an isotope of hydrogen (one proton) whose nucleus contains a proton and a neutron, at a level of D/H = (0.95 ± 0.06) percent, which is more than ten times higher than in known comets. In addition, the 12C/13C isotope ratios (141–191 for CO2 and 123–172 for CO) exceeds typical values found in the Solar System, as well as nearby interstellar clouds and protoplanetary disks. Such extreme isotopic signatures indicate formation at freezing temperatures below 30 degrees Kelvin in a relatively metal-poor environment, early in the history of the Milky Way galaxy. Astronomers refer to elements heavier than hydrogen and helium (both of which are relics of the Big-Bang), as `metals’. When interpreted in terms of models for chemical evolution, the carbon isotopic composition implies that 3I/ATLAS formed 10–12 billion years ago. Hence, 3I/ATLAS is interpreted in this paper as a fragment of an ancient planetary system with a low metallicity. Isotopic ratios observed in the gas plume around 3I/ATLAS compared with Milky-Way and Solar System observations for deuterium (neutron plus proton) to hydrogen (single proton) ratio: D/H (top) and carbon isotopes 12C/13C (bottom). (Image Credit: M. Cordiner et al. 2026)The second paper, led by Cyrielle Opitom, reports the measurement of carbon and nitrogen isotope ratios in 3I/ATLAS from observations of the cyanide (CN) molecule, based on observations with the Very Large Telescope in Chile. The data implies a 12C/13C ratio of 147(+87/-40) and a 14N/15N ratio of 343(+454/-124). The 14N/15N ratio is more than twice above the value of about 150 usually measured for solar system comets. The 12C/13C is marginally higher than the values usually measured for solar system comets and in the interstellar medium. Similarly to the first paper, the authors here conclude that their measurements might indicate an origin from an old, low-metallicity star. However, both papers do not realize that a low-metallicity origin for 3I/ATLAS generates untenable tension with its inferred mass and abundance. Analysis of the latest data from the Hubble Space Telescope on 3I/ATLAS (reported here), suggests a nucleus radius of about 1.3 kilometers and a number density of about 0.007 per AU cubed (where AU is the Earth-Sun separation). This implies 30 trillion objects and a total mass of 100 Earth masses within the volume of the Oort cloud out to 100,000 AU around the Sun — which is roughly half way to the nearest star, Proxima Centauri. Only a tenth of all stars in the Milky-Way’s thick disk has a metallicity that is 10 times below the solar value (as discussed here). By restricting the source population of 3I/ATLAS to these low-metallicity stars, I find that each of these low-metallicity stars must produce 1,000 Earth masses in objects the size of 3I/ATLAS. Most of the material in the gas plume around 3I/ATLAS is made of carbon or oxygen based molecules (as reported here), suggesting that the object is made of heavy elements, considered as metals. This mass budget calculation requires the production of 0.003 solar masses in 3I/ATLAS-like objects per star. However, solar mass stars with a tenth of the solar metallicity have only 0.002 solar masses in heavy elements within them. In addition, their planetary systems which serve as the natural birth sites of interstellar objects, are expected to originate from debris disks that contain at least ten times less mass than the host star. On top of that, one expects a mass spectrum of ejected interstellar objects with at least ten times more mass in objects with masses that are orders of magnitude different from those of 3I/ATLAS (as discussed here). This calculation implies that low-metallicity stars miss the required mass budget by at least two orders of magnitude and cannot account for the interstellar population of 3I/ATLAS-like objects even if they ejected all their heavy elements to interstellar space. The more data we get about 3I/ATLAS, the more puzzling it looks. As Forrest Gump said in the 1994 film: “Life is like a box of chocolates, you never know what you’re gonna get.” ABOUT THE AUTHOR (Image Credit: Chris Michel, National Academy of Sciences, 2023)Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. The paperback edition of his new book, titled “Interstellar”, was published in August 2024. Professional website: https://lweb.cfa.harvard.edu/~loeb/ Social media: https://avi-loeb.medium.com/ https://www.youtube.com/@ProfessorAviLoeb https://open.spotify.com/show/1zhndXkvSY2b8FdjspFpCd https://x.com/ProfAviLoeb View the full article

A symmetric structure of a sunward anti-tail plus three equally-separated jets is apparent near the nucleus of 3I/ATLAS, after applying the Larson-Sekanina rotational gradient filter to two exposures by the Hubble Space Telescope on 2025–12–27. (Image Credit: T. Scarmato and A. Loeb 2026).After a four-hour interview with AJ Gentile in Las Vegas yesterday, I returned to Boston at midnight and before my morning jog — I answered the following set of questions from a journalist about the interstellar object 3I/ATLAS: - You previously estimated the likelihood that 3I/ATLAS is the creation of an alien civilization. A large body of observational data has now been accumulated. Has this probability increased or decreased? When 3I/ATLAS was discovered in July 2025, I gave it a rank of 4 on the Loeb Classification scale of interstellar objects (defined here), where 0 means a natural comet and 10 means alien technology that poses a major threat to humanity. 3I/ATLAS displayed rare geometric anomalies. Its trajectory was leading towards the inner solar system, within 5 degrees of the orbial plane of the planets around the Sun, and with a rotation axis that is nearly aligned with the direction of the Sun. It also featured a prominent anti-tail in the direction of the Sun rather than a commonly observed cometary tail of dust and gas pushed away by the solar radiation and wind. Before perihelion, the plume of gas around 3I/ATLAS featured nickel with much less iron as found in industrially produced nickel alloys, and after perihelion it featured methane (CH4), a biosignature whose volatility lies between carbon dioxide (CO2) and carbon monoxide (CO) — both of which well detected well before methane. Forty post-perihelion images obtained by the Hubble space telescope, showed a circular glow of reflected sunlight plus a symmetric system of three jets, equally separated from each other around the nucleus (as summarized here). Are these technological thrusters or merely a position coincidence of three random pockets of ice on the surface of a rocky iceberg? Given all that we have learned so far (summarized as 18 anomalies listed here), and assuming that nothing unusual will happen near Jupiter, I would reduce the rank of 3I/ATLAS now to 3 on the Loeb Scale, because its natural cometary behavior is accompanied by multiple unexplained anomalies. In that case, 3I/ATLAS could also Trojan Horse, namely a hitchhiked interstellar iceberg on a selected path through the solar system — on which technological equipment was installed by an extraterrestrial civilization. - Did you notice that 3I/ATLAS came from the same region of the sky where a strange radio signal was received in 1977? What was this signal? An attempt to warn of its approach? A simple technical transmission? Yes, I was first to point out this coincidence of 9 degrees alignment between the arrival direction of 3I/ATLAS and the “Wow! Radio Signal” detected in 1977, in an essay I posted here. This chance alignment has a random probability of less than a percent. Attempts to detect radio transmission from 3I/ATLAS towards Earth on a few specific days during the past six months failed. We do not know what the “Wow! Signal” means; it could have been transmission from a companion gadget to 3I/ATLAS or from its the senders. This coincidence represents one additional rare anomaly about 3I/ATLAS. - Are there any signs that 3I/ATLAS left “observers” near Earth or will do so near Jupiter? 3I/ATLAS will arrive at a closest distance of 53.6 million kilometers from Jupiter on March 16, 2026. Coincidentally, this distance is close to the so-called `Hill radius’, where Jupiter’s gravity dominated over the Sun’s tidal gravity (as I pointed out here), allowing for the deployment of probes in a gravitationally bound orbits around Jupiter as long as they receive an appropriate kick that will cancel the fast velocity of 3I/ATLAS at 66 kilometers per second relative to Jupiter. So far, we had not seen evidence for the release of such objects but it would make sense to check with future imaging data obtained by the Juno, Juice and Europa Clipper spacecraft around Jupiter, whether new small satellites were added around Jupiter. So far, we have not noticed any related objects near Earth. - Since 3I/ATLAS was an active source of organic matter, could it have “infected” the Solar System with its own kind of life? In that case, all we can do is wait for the “new” life to displace our “old” one and simply return as if it were its own. After perihelion, 3I/ATLAS released organic molecules which are biomarkers, as I discussed here. Is this a sign that 3I/ATLAS carries life? For a civilization that has the ambition of becoming an interstellar gardener, it would make sense to deposit microbes inside a natural iceberg that has the nutrients needed for life, so that when the iceberg gets close to a star like the Sun it would shed these seeds on a potentially fertile ground like Earth. Our civilization could follow this vision by depositing a capsule with microbes, warmed by a power source, on a future interstellar iceberg, at a cost that matches the budgets of our space agencies. However, in an essay posted here, I pointed out that the material shed by 3I/ATLAS will never reach Earth because it is pushed away from Earth by the solar radiation and wind and because of the fact that 3I/ATLAS passed on the other side of the Sun relative to Earth. - If we assume that 3I/ATLAS is an artificial object, was it controlled by artificial intelligence, or by beings that “awakened” during the flight and will now fall asleep again? The journey from distant stars takes billions of years so I would expect artificial intelligence (AI) to guide interstellar travel. However, biological passangers are also possible if their life expectancy was extended indefinitely by AI-assisted medicine. - Earthlings were unprepared for an encounter with another civilization: scientists were immersed in debate and mutual accusations. It turns out we’re unable to contact 3I/ATLAS or catch up with it, and we don’t even want to. We’ve failed the test. What does this mean for the future? The Rubin Observatory in Chile is expected to discover dozens of new interstellar objects. This argues for a coordinated scientific effort to detect new anomalous objects like 1I/`Oumuamua or 3I/ATLAS 6–12 months in advance of their arrival near Earth, so that we can design space missions to intercept them. This calls for a comprehensive network for the discovery and characterization of interstellar objects, as discussed here. The collected data will help policy makers calibrate future objects on the Loeb Scale, and initiate an appropriate defense of Earth from potential threats of alien technology. We must be prepared to assess the risk from black swan events even if we expect most interstellar objects to be natural icebergs. - If we don’t change anything, will Earth be subjugated to another intelligence, or simply abandoned to its fate? When might this happen? It is possible that Earth is already being visited, if claims about Unidentified Anomalous Phenomena (UAP) in the Earth’s atmosphere or oceans are correct. I am leading the Galileo Project (discussed most recently here) that operates three new observatories in search for extraterrestrial artifacts near Earth. If we discover anything, I will be better positioned to answer your question with substantive information. - Could other civilizations infiltrate our (our own) artificial intelligence and subordinate our lives to their own interests? This is a concern. When engaging in a blind date, you never know whether your dating partner is friendly or a serial killer. I am optimistic that we will benefit more than we will lose from encountering a superior intelligence. You may call me romantic. I believe that the best is yet to come. - Will “contact” even happen as it’s described in science fiction (a craft lands on Earth, creatures emerge, journalists take photographs, and leaders shake hands)? It is very unlikely that our imagination is sufficiently evolved to anticipate the characteristics of an encounter. The scripts of science-fiction writers in Hollywood are based on a training data set limited to Earth. Interstellar visitors have a much larger training data set, because there is much more real estate beyond Earth. This is why we should always look up at the vast expanses of cosmic space (measured in billions of light years) and time (measured in billions of years) if we wish to learn something new. Even in our most ambitious scientific projects, we study the “known unknowns” but our biggest step forward will result from finding “unknown unknowns”. These are things that we do not even realize that we do not know. ABOUT THE AUTHOR (Image Credit: Chris Michel, National Academy of Sciences, 2023)Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. The paperback edition of his new book, titled “Interstellar”, was published in August 2024. Professional website: https://lweb.cfa.harvard.edu/~loeb/ Social media: https://avi-loeb.medium.com/ https://www.youtube.com/@ProfessorAviLoeb https://open.spotify.com/show/1zhndXkvSY2b8FdjspFpCd https://x.com/ProfAviLoeb View the full article

(Image credit: Greg Wyatt)In his Critique of Judgment (1790), Immanuel Kant famously asserted that “there will never be a Newton of the blade of grass, because human science will never be able to explain how a living being can originate from inanimate matter”. In a 21st century context, this philosophical insight means that while cosmologists understand the physical laws governing the movement of matter and radiation since the Big-Bang, it is far more challenging for astrobiologists to explain the origin of life from the same physical principles. The emergence of life-as-we-know-it, and in particular intelligent life, remains one of the most intriguing puzzles about the history of Earth. The scientific folklore asserts that humans emerged as a result of fortunate circumstances out of a soup of chemicals on early earth when our last universal common ancestor (LUCA) formed 4.2 billion years ago. If so, it is common sense to assume that similar outcomes should result out of similar circumstances on exoplanets. The census of planets around other stars suggests that there might be billions of Earth-Sun analogs. It is arrogant to believe that humans are unique or special or, in particular, that Elon Musk was the most accomplished space entrepreneur since the Big Bang, 13.8 billion years ago. (Image credit: Greg WyattIt is a matter of common sense to search for the siblings in our family of intelligent civilizations within the Milky-Way galaxy. Some of our siblings might be more accomplished than we are because they had the benefit of discovering the laws of quantum mechanics and gravity billions of years before us, since the Sun existed for the last third of cosmic history. By finding them, we can learn from their insights and rather than invest 2.4 trillion dollars per year in military budgets worldwide we might be inspired to invest similar funds in space exploration. (Image credit: Greg WyattGiven the billions of Earth-Sun systems, we are probably not at the top of the food chain of the Milky-Way galaxy. Lower lifeforms, like microbes, are probably far more abundant, just like mediocre dating partners. But we should aim high, not low, when seeking a partner. It is much better to seek a partner who is more intelligent than we are because their insights will inspire us to do better. (Image credit: Greg Wyatt)Without seeking evidence, we will remain ignorant about our most accomplished sibling civilizations. Finding them may inspire us to invest in space science that will promote our interstellar journeys. Launching “Noah’s Spaceships” that carry humans to interstellar space would constitute monuments for humanity’s childhood home after the brightening Sun will evaporate all oceans on Earth in a billion years. These vehicles will carry our only documented memories billions of years from now. Nobody would mourn the disappearance of the human species from the surface of Earth. Here’s hoping that we will be ultimately listed in the history books of the Milky Way as an interstellar species. *** In this essay, I featured four amazing watercolors from a series created by the celebrated artist, Greg Wyatt. These watercolors incorporate inspiring statements by Boethius. This is the sixth in a sequence of essays, where Greg and I collaborate on the interface between art and science. The first essay in this series, titled “Music of the Cosmic Spheres,” appeared here; the second essay, titled: “Cosmic Waterfalls in Spacetime Cliffs,” appeared here; the third titled “Missing Elements in the Cosmic Jigsaw Puzzle,” appeared here; the fourth essay, titled: “Why Do We Exist?”, appeared here, and the fifth titled “Inspiration from the Stars”, appeared here. ABOUT THE AUTHOR (Image Credit: Chris Michel, National Academy of Sciences, 2023)Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. The paperback edition of his new book, titled “Interstellar”, was published in August 2024. Professional website: https://lweb.cfa.harvard.edu/~loeb/ Social media: https://avi-loeb.medium.com/ https://www.youtube.com/@ProfessorAviLoeb https://open.spotify.com/show/1zhndXkvSY2b8FdjspFpCd https://x.com/ProfAviLoeb View the full article

An equal-area projection map of impact locations (red dots) for 343 meteors with known velocities and impact energies recorded in NASA’s Center for Near-Earth Object Studies (CNEOS) Fireball and Bolide Database from 1994 February 1 to 2026 January 1. The estimated diameter of each object (ranging from 0.75 to 24 meters) is indicated by the relative size of its dot. The spatial distribution of impacts over Earth’s surface appears nearly uniform. (Image credit: I. Cho et al. 2026)Every year, an explosion with an energy output comparable to the Hiroshima atomic bomb occurs in our atmosphere without advance warning (as reviewed here). But in difference from the historic Hiroshima explosion on August 6, 1945, these annual explosions are not mentioned as breaking news because they involve a natural rock that measures a few meters in diameter which burns up in a fireball at an altitude of 30–50 kilometers. In contrast to the atomic bomb which was intentionally detonated 600 meters above the city Hiroshima in order to maximize damage, the high altitude of meteor explosions makes most of them unimpactful for life on Earth. Nevertheless, under rare circumstances some small meteoritic fragments trigger reported damage on the ground once every few years. For example, on June 26, 2025 a meteorite, later determined to be from a one-ton, 4.56-billion-year-old rock, tore through the roof of a house near Atlanta. The fragment was small, about the size of a cherry tomato, but it left a hole in the roof, went through air ducts, and slammed into the concrete floor. In May 2023, a metallic meteorite, approximately the size of a grapefruit, crashed through the roof of a home, causing minor structural damage to the roof and floor but no injuries. Given that house cover only a small fraction of Earth, numerous such incidents must occur every year over uninhabited areas. Those who worry about the risk of being hit by a cosmic impactor from the sky, might wonder whether we could receive an advance warning about this risk. After all, we are used to weather forecasts which warn us about the risk from droplets of rain falling from the sky. Could we imagine a future in which the daily forecast will also include a warning about a small meteor impact on a particular region? Obviously, no umbrella can withstand a meteor impact, but resident in the risk area might chose to leave the region in advance of the impact. A new paper posted here, shows that the NSF-DOE Rubin Observatory will be able to warn earthlings about 1 in 25 of all imminent impactors larger than a meter, a few days in advance. The paper simulated the expected discovery performance for imminent impactors using 343 meter-size objects previously recorded in NASA’s CNEOS database as fireballs in the Earth’s atmosphere. The simulations indicate that the Rubin Observatory will discover at least one meter-size imminent impactors per year, representing about 4% of all Earth impactors larger than a meter in diameter and almost doubling the current discovery rate of imminent impactors. The median time of discovery is 1.57 days before impact. The spatial distribution of the 11 previously discovered imminent impactors is biased towards the Northern Hemisphere, where the observatories that discovered them are located. By observing the southern sky, the Rubin observatory will provide an important counterpart to existing asteroid surveys which are primarily located in the Northern Hemisphere. Aside from information about the Solar system, material falling from the sky could also educate us about the makeup of our neighbors’ yards. About one in a thousand impactors might be interstellar in origin. Here’s hoping that among the interstellar meteors, we might find one day a Voyager-like meteor that was launched by an extraterrestrial civilization on the other side of the Milky-Way galaxy billions of years ago. Such an object would resemble an odd tennis ball that came from a neighbor’s yard. Meteor experts might respond to it like cave dwellers confronted for the first time with a cell phone, saying: “This is a rock of a type that we had never seen before.” ABOUT THE AUTHOR (Image Credit: Chris Michel, National Academy of Sciences, 2023)Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. The paperback edition of his new book, titled “Interstellar”, was published in August 2024. View the full article

Is the Mysterious Cylinder on Mars, Photographed in 2022 by the Curiosity Rover, a Human-Made Debris?A raw image from the Mast camera (Mastcam) onboard NASA’s Mars rover Curiosity, taken on 2022–08–07 at 20:58:23 UTC. (Image credit: NASA)A raw image from the Mast camera (Mastcam) onboard NASA’s Mars Curiosity rover, taken on 2022–08–07 at 20:58:23 UTC, displays a mysterious cylinder buried in the Martian regolith of the Paraitepuy Pass — a narrow gap in the Gale Crater situated on the slopes of Mount Sharp. This puzzling object was brought to my attention by Dr. Jan Špaček — who studies signatures of life on Mars and Professor Carol Cleland — who studies anomalies from a philosophical perspective. The object was publicly discussed in detail, for example here. I wrote back to Jan and Carol that anomalies are best analyzed in the open with full disclosure of all available data, since such discussions might motivate scientists to collect additional data that would resolve their mystery. The cylinder can be seen in multiple images from both the Mastcam left and Mastcam right high-definition color cameras at different focal distances within the NASA, JPL, and WUSTL repositories. Related data was documented by NASA here, by JPL here (3556MR1025170721700585C00_DRCL), and by WUSTL here (Sol 3556, object 713174794). The cylinder was imaged from various angles here, here and here. It was identified in raw images of the Curiosity MSL analyst notebook but was not featured on the public mission website at the time of its discovery. The shiny object has a perfectly round cylindrical shape with a length of about 20 centimeters and a flat end. The most likely explanation is that it corresponds to human-made debris. Objects found by rovers that appear artificial are typically identified as debris from the mission’s own landing system, such as parts of the Sky Crane or heat shield that may have been carried by winds or scattered during the rover’s descent in 2012. This particular anomalous cylinder could be a bit of wiring or wheel material from Curiosity itself. The rover has shed small pieces during its operations, and similar anomalies in past images have been traced back to mission hardware. The Curiosity rover is approximately the size of a small SUV, measuring roughly 3-meters-long, 2.8-meters-wide, and 2.2-meters-tall. It weighs nearly 899 kilogram and features a 2.1-meters-long robotic arm and wheels with a 50.8-centimeter diameter. The Martian harsh environment can also shape rocks into unusual forms, like the “blueberries” (hematite spherules) or gypsum crystals seen elsewhere in Gale Crater. NASA has not officially commented on this mysterious cylindrical object. Currently, the Curiosity rover is exploring the lower slopes of Mount Sharp within the Martian Gale Crater, about 8 kilometers away from the location of the cylinder. To clarify the mystery, it would make sense to go back to its location and examine it from up close. At Curiosity’s maximum speed of 0.16 kilometers per hour, the rover could return within a couple of days back to the location of the cylinder. Should we just assume that the mysterious cylinder is human-made debris and move on or turn back the rover to figure out whether its origin is different? ABOUT THE AUTHOR (Image Credit: Chris Michel, National Academy of Sciences, 2023)Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. The paperback edition of his new book, titled “Interstellar”, was published in August 2024. Professional website: https://lweb.cfa.harvard.edu/~loeb/ Social media: https://avi-loeb.medium.com/ https://www.youtube.com/@ProfessorAviLoeb https://open.spotify.com/show/1zhndXkvSY2b8FdjspFpCd https://x.com/ProfAviLoeb View the full article

Space Companies Did Not Pollute Our Night Sky for Billions of Years and Should Not Do So in the FutureSatellite streaks are evident in this long-exposure image of the sky over the NSF-DOE Rubin Observatory in Chile. (Image credit: Rubin Observatory/NOIRLab/SLAC/AURA/W.O’Mullane)If a future catastrophe will wipe out our technological civilization from the surface of Earth, will there be a technological relic that will survive intact for billions of years? One form of such relics are satellites above the altitude of geostationary orbits at 35,786 kilometers. These relics will continue to orbit the Earth long after they stop operating, since they do not have significant drag on the Earth’s atmosphere. Given that we had not discovered any prehistoric satellites at these high altitudes, we can safely conclude that there was no SpaceX-like company on Earth for billions of years before Elon Musk founded SpaceX in 2002. If the dinosaurs had launched a geostationary satellite, it could have still been up there today. If the Roman Empire had been able to launch a satellite with an orbital altitude as low as 1,200 kilometers, then this Roman satellite might have been falling back to Earth and burning up in the Earth’s atmosphere just now. Space archeology informs us that no space launch capabilities were available to the dinosaurs or the ancient Romans. (Image credit: UN/ESA)But with advanced technology comes responsibility! This does not only apply to artificial intelligence systems, a hot topic for today’s policy makers in Washington DC, but also to satellites around Earth. Let me explain. The lack of a large population of high-altitude pre-historic satellites allowed humans to study the Universe with ground-based telescopes and understand how we came to exist from the initial conditions set by the Big Bang, 13.8 billion years ago. This intellectual accomplishment started with Galileo Galilei who spotted the moons of Jupiter through his telescope and realized that the Earth is not at the center of the Universe. Following his pioneering work, humanity’s best telescopes were placed on top of remote mountains — where they can effectively avoid the contamination of the night sky by light pollution from human made activities. Largely because of SpaceX and other companies, this is not possible any more. Our space economy is now gearing up to fill the dark night sky with lights. Communication satellites are already leaving unavoidable marks on the images obtained by ground-based telescopes, as they reflect sunlight outside the Earth’s shadow. Their motions around the Earth imprint prominent streaks in the (15+15) second exposures taken by the state-of-the-art NSF-DOE Rubin Observatory in Chile (as discussed recently here). But the worst is yet to come. A new space-mirror company is requesting authorization to pollute the night sky intentionally! Reflect Orbital is a start-up company proposing a constellation of up to 50,000 satellites by 2035, to provide a sunlight-on-demand service to consumers. This would involve reflecting beams of sunlight with a diameter of about 5 kilometers onto Earth’s surface to provide lighting or solar energy to the customers. (Image credit: Gaspar Bakos, Princeton University)This potentially new source of light pollution could affect astronomical observations irrespective of their elevation or distance from city lights on the surface of Earth. Rayleigh scattering in the Earth’s atmosphere, both from the incoming beam and from reflected light, is ignored by the company and could result in an enormous skyglow from a brightly illuminated area, the size of 650 football stadiums. This technology will introduce sustained artificial dusk and dawn conditions across landscapes, in addition to hours-long bursts of daytime brightness. Reflect Orbital has submitted an application to the Federal Communications Commission (FCC) to launch a testing satellite, EARENDIL-1. Their demonstration satellite would produce a beam about as bright as the full Moon, while the full constellation could produce illumination comparable to that of the Sun at high noon. The FCC has opened a public comment period until March 9th, 2026, giving the public an opportunity to voice their thoughts and concerns about federally approved projects. If you care about the above-mentioned risk to the dark night sky, please sign and share the open letter opposing this initiative, written by DarkSky International, and consider submitting a public comment to the FCC by March 9th, 2026. More details, compiled by Sarah Thiele & Gaspar Bakos from Princeton University, are available here. Past terrestrial civilizations did not pollute the night sky for billions of years and space companies like Reflect Orbital should not be allowed to do so in the future. The species of non-avian dinosaurs was extinguished as a result of a giant asteroid impact 66 million years ago. If consulted, these dinosaurs would have agreed with this sentiment. They dominated the Earth without looking up through telescopes. The lesson is simple: if our species will not be able to survey the dark sky in search for near Earth asteroids because of light pollution, it might not survive for long in cosmological terms. We tend to arrogantly assume that we are more intelligent than any life form that ever existed on Earth, while at the same time we promote technologies that could lead to our demise. This suggests a new solution to Enrico Fermi’s paradox concerning extraterrestrials: “Where is everybody?” Extraterrestrial technological civilizations might have blinded their outward-looking Rubin-like telescopes with light pollution and went extinct in the same way that the dinosaurs did. Extending the Darwinian “survival of the fittest” to the cosmos, suggests that only civilizations which were intelligent enough to block companies like Reflect Orbital survived. The FCC could decide whether our civilization has a chance of fulfilling the Vulcan salute from Star Trek: “live long and prosper”. ABOUT THE AUTHOR (Image Credit: Chris Michel, National Academy of Sciences, 2023)Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. The paperback edition of his new book, titled “Interstellar”, was published in August 2024. Professional website: https://lweb.cfa.harvard.edu/~loeb/ Social media: https://avi-loeb.medium.com/ https://www.youtube.com/@ProfessorAviLoeb https://open.spotify.com/show/1zhndXkvSY2b8FdjspFpCd https://x.com/ProfAviLoeb View the full article

The Rubin Observatory Could Discover Corner Reflectors or Artificial Lights in the Outer Solar System(Image credit: YIC-electronics)A week ago, the Rubin Observatory initiated the release of its much-anticipated flood of data from its 3.2 gigapixel camera (as announced here). Solar-system astronomers are accustomed to discovering asteroids by detecting the reflection of sunlight from their surface. However, a class of objects with the same surface area are potentially detectable to much greater distances in the outer solar system. They could be discovered, for the first time, by the Rubin Observatory. Natural objects which reflect sunlight get dimmer inversely with distance to the 4th power at distances that are much larger than the Earth-Sun separation. The reason is simple. The flux of sunlight impinging on their surface declines inversely with distance squared and the observed flux as a result of reflection off their surface declines by another factor of inverse distance squared. Combining these factors implies that asteroids or the nuclei of interstellar objects get dimmer inversely with heliocentric distance to the 4th power. On the other hand, a source that generates its own light, like a spacecraft or a city, would brighten inversely with distance squared as it approaches us from the outer solar system. This resembles the way that a lamppost brightens as we approach it from a dark street. The difference between scaling with distance to the 4th and 2nd powers can distinguish between a natural and a technological object. In 2012, I published a paper here with Ed Turner from Princeton University, which showed that existing optical telescopes and surveys can detect artificially-illuminated objects comparable in total brightness to a major terrestrial city out to the outskirts of the Solar System. Since orbital parameters of Kuiper belt objects are routinely measured to exquisite precisions, we proposed to measure the variation of the observed flux from such objects as a function of their changing orbital distances. This idea is particularly feasible now with the Rubin Observatory. If objects with an inverse-square brightening law are found, follow-up observations can measure their spectra to determine whether they are illuminated by artificial lighting. The search can also be extended beyond the Solar System with future telescopes, which would be capable of detecting phase modulation due to very strong artificial illumination on the night-side of planets as they orbit their parent stars. Another interesting class of objects which would follow the inverse-square brightening law are corner reflectors along the Sun-Earth axis. A corner reflector is a passive retroreflector consisting of three mutually perpendicular, intersecting flat surfaces that reflect waves directly back toward their source, regardless of the incidence angle. They are essential for enhancing radar visibility, satellite tracking, and laser ranging. Corner reflectors were particularly helpful in measuring the distance between the surfaces of the Earth and the Moon using lasers. The distance is calculated from the round-trip time of laser pulses propagating at the speed of light, which are reflected back to Earth by the Moon’s surface or by reflectors on the Moon. Three reflectors were installed by the United States’ Apollo program, two by the Soviet Lunokhod 1 and 2 missions, and one by India’s Chandrayaan-3 mission. The precise distance measurements so far imply that Newton’s constant does not change by more than a part in ten trillion per year (as reported here and here). Now, consider a corner reflector created by another technological civilization. If that corner reflector happens to be aligned with the Sun-Earth axis, it will follow the inverse-square brightening law because it will reflect rays of sunlight back to where they came from, allowing an observer on Earth to detect them. The shadow of the Earth has a negligible effect at large distances, because the surface area of Earth is 12,000 times smaller than that of the Sun. Our situation resembles a fly hovering over a lamppost and observing the reflection of light from a corner reflector in a dark street. As long as the Earth is observed to transit the Sun from the vantage point of the corner reflector, we would observe the corner reflector to follow the inverse-square brightening law. This favorable geometry selects a swath that covers 0.47% of the sky, the ratio between the radius of the Sun and the Earth-Sun separation. In other words, only one out of 214 corner-reflectors that are randomly distributed around the Sun will follow the inverse-square brightening law from the Earth’s vantage point. Gladly, these corner reflectors will all be detectable at nighttime when the body of the Earth blocks the sunlight and allows a ground-based telescope to search for them. They would all appear in opposition to the Sun within a cone of 0.25 degrees, corresponding to the angular radius of the Sun from Earth. The Rubin observatory or other survey telescopes resemble the eyes of the fly havering near the lamppost and looking away for reflected light from objects in the dark street. A corner reflector can be distinguished from a source of light by its spectrum matching that of sunlight and by its position in the sky being in opposition to the Sun. Here’s hoping that the Rubin Observatory will show evidence for either sources of artificial light or a corner reflector. Any such detection will surely make our life on Earth far more exciting. ABOUT THE AUTHOR (Image Credit: Chris Michel, National Academy of Sciences, 2023)Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. The paperback edition of his new book, titled “Interstellar”, was published in August 2024. Professional website: https://lweb.cfa.harvard.edu/~loeb/ Social media: https://avi-loeb.medium.com/ https://www.youtube.com/@ProfessorAviLoeb https://open.spotify.com/show/1zhndXkvSY2b8FdjspFpCd https://x.com/ProfAviLoeb View the full article

Orbit of 3I/ATLAS relative to the Sun in the ecliptic plane of the Earth around the Sun (with 1au being the Earth-Sun separation). Closest approach (perihelion) is marked by a yellow star, and the endpoints of the observational arc used for the orbit determination are indicated by open circles. Gray shading denotes the region where 3I/ATLAS goes under the orbital plane of Earth around the Sun, as the retrograde orbit of 3I/ATLAS is inclined by 5 degrees relative to the ecliptic. The Sun and the orbits of the major planets out to Jupiter are shown for reference. (Image credit: F. Spada, M. Królikowska and L. Dones, in a paper posted here on March 3, 2026)Today, a new paper reported the most comprehensive analysis of the non-gravitational acceleration of the interstellar object 3I/ATLAS. Its results differ from the official NASA report, posted on the Jet Propulsion Laboratory (JPL) Small Body Database here. Whereas NASA reports a radial acceleration component away from the Sun that is 5 times larger than the tangential component along the direction of motion of 3I/ATLAS, the new paper derives similar amplitudes for the radial and tangential components. The new analysis suggests that 3I/ATLAS is pushed sideways and not simply away from the Sun — as implied by the official analysis of Davide Farnocchia from NASA/JPL. Yes, official statements from NASA can be wrong. Science is a learning experience. Does a large non-radial acceleration make sense? Yes, according to high-resolution images of 3I/ATLAS. Observations from August 2026 when 3I/ATLAS was approaching the Sun, reported here the existence of collimated, high-latitude jets that display a periodic wobble consistent with nucleus rotation. This morphology indicated localized sources of mass loss rather than uniform sublimation of the nucleus, which could trigger significant non-radial acceleration. In two papers that I co-authored with Toni Scarmato here and here, we removed the circular glow around the nucleus in the highest-resolution post-perihelion images of 3I/ATLAS from the Hubble Space Telescope, and discovered three symmetrically-separated mini-jets in addition to a prominent sunward jet (anti-tail), modulated by a 7.1 hours rotational period and consistent with a spin-axis orientation within 20 degrees of the sunward direction. Such a configuration naturally favors strongly directional gas and dust emission, capable of generating a transverse acceleration component which is comparable in magnitude to the radial one. It would be interesting to use the geometry of this jet system and demonstrate that the non-gravitational force on the nucleus yields a tangential acceleration comparable in magnitude to the radial one, based on the mass outflow carried by the different jets. The conclusions of the new paper are based on examining a variety of orbital solutions that implement symmetric, time-offset, and asymmetric radial dependence of the outgassing relative to perihelion. The radial and normal components of the non-gravitational acceleration (labeled, A1 and A3) are broadly consistent across all solutions, whereas the transverse component (A2) is more sensitive to data selection, parameter correlations, and orbital phase coverage. The magnitude of the non-gravitational acceleration can be used to constrain the nucleus diameter of 3I/ATLAS, which most recently was inferred here to be 2.6 kilometers. The total magnitude of the non-gravitation acceleration is small, about a micrometer (a percent of the width of a human hair) per second squared. It corresponds to a spatial offset by half the radius of the Moon over a period of a month. This offset is smaller than the Earth-Sun separation by a factor of 200,000 and is therefore of negligible significance in shifting the path of 3I/ATLAS relative to the Sun or the planets. The origin of the symmetric system of 3 mini-jets, separated equally by 120 degrees from each other, remains enigmatic. Does it constitute a technological signature of thrusters? We do not know. *** Before my morning jog at sunrise, I received the following uplifting message from the poet Alan Wagstaff in New Zealand. “Dear Dr Loeb, You said in a recent essay: ‘This could be done by attending a science-fiction movie, subscribing to belief cults on social-media, using metaverse goggles or taking recreational drugs. These virtual realities bend constraints at will and give rise to a pleasing experience that makes us happy. ‘ May I add, science imaginings sometimes provide the impulse which launches clear thinkers into science proper? So long as fact and fiction are not conflated, this is positive. As Robert H. Goddard once said in a letter to H. G. Wells: “In 1898 I read your ‘War of the Worlds’. I was sixteen years old … It made a deep impression … The spell did not break … and I took up physics.” (Goddard went on to become a foundational figure in rocketry and launch physics, eventually pioneering liquid-fueled rockets that laid the groundwork for the Space Age.) In the light of this, I revisited my poem ’Three Magi’ and honed it. Perhaps it will light a spark somewhere that will provoke real science in some young student’s mind. Kind regards Alan” ABOUT THE AUTHOR (Image Credit: Chris Michel, National Academy of Sciences, 2023)Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. The paperback edition of his new book, titled “Interstellar”, was published in August 2024. Professional website: https://lweb.cfa.harvard.edu/~loeb/ Social media: https://avi-loeb.medium.com/ https://www.youtube.com/@ProfessorAviLoeb https://open.spotify.com/show/1zhndXkvSY2b8FdjspFpCd https://x.com/ProfAviLoeb View the full article

A Scientific Alternative to Government Disclosure: The Galileo Project is Now Capable of Discovering UAPThe triangulation-based path of an airplane (red) provides a distance measurement that is within 10% of its actual path (green), based on the latest analysis by the Galileo Project. (Image credit: Richard Cloete and Regina Sarmiento, Galileo Project)A few days ago, I celebrated my birthday by giving the colloquium at Harvard’s Institute for Thery and Computation, for which I served as director over the past twenty years. This hour-long lecture, available here, garnered by now of order ten thousand views. It overviews of the research performed within the Galileo Project that I am leading. The goal of the Galileo Project is to bring the search for extraterrestrial technological artifacts to the mainstream of transparent, validated and systematic scientific research. The Galileo Project currently operates three observatories in Massachusetts, Pennsylvania and Nevada, with a future observatory planned for Indiana. These observatories monitor the entire sky continuously in the infrared, visible, radio and audio bands, and record data on millions of objects. The data is analyzed by machine learning software, trained to discover outliers with unfamiliar characteristics. The same airplane is observed as a white dot in the lower-right quarter of the image on the left-hand-side and as a white dot near the center of the image on the right-hand-side (along with three birds flying above it). These two images were taken by two infrared cameras separated by about 10 kilometers. The comparison of the images, along with accurate time stamps, allows to infer the distance of the airplane to within an accuracy of better than 10%. (Image credit: Regina Sarmiento, Galileo Project)For the first time since I co-founded the Project together with Dr. Frank Laukien in July 2021, the Galileo research team under my leadership has reached a major milestone this month. We are now capable of measuring distances to objects in the sky to better than 10%, by observing them from different directions with multiple units separated by 10 kilometers from each other. This method of triangulation, enabled by accurate time stamps, allows us to measure the three-dimensional velocity and acceleration of objects and determine whether any of them lies outside the performance envelopes of human-made technological objects, such as drones, balloons, airplanes, helicopters or satellites. The goal of the Galileo research team is to figure out whether there are extraterrestrial technological visitors in our backyard. As of now, the Galileo observatories can discover Unidentified Flying Objects (UFOs) or Unidentified Anomalous Phenomena (UAP). Any such discovery, substantiated by scientific-quality data, will be shared through the standard scientific protocol with the public. Instead of waiting for disclosure of classified information on UAP or UFOs, the Galileo research team is simply observing the sky. We do not need to rely on the official channels of NASA or the U.S. government to tell us whether we are being visited, for the same reason that we did not need the official declaration of the Vatican in 1992 to learn that the Earth moves around the Sun. The Vatican’s official announcement came 382 after Galileo Galilei reached the same conclusion by looking at the sky through his telescope. For 65 years, the SETI community has been searching for an electromagnetic signal from a distant star system while stubbornly avoiding the search for interstellar visitors near Earth — including a ban on discussing anomalous near-Earth objects at their conferences (as recommended by a committee chaired by Dr. Jason Wright from Penn State University). During the same period of time, the Pentagon and the U.S. intelligence agencies searched the sky for any flying objects from adversarial nations. These government agencies could have therefore been the first to record anomalous objects in the Earth’s atmosphere. Mainstream astronomers are focused on the search for the chemical fingerprints of microbes in the atmospheres of exoplanets. Indeed, microbes are likely to be far more abundant than intelligent beings, but their chemical fingerprints are challenging to detect unambiguously. It makes sense to harvest low-hanging fruits in our backyard while we invest ten billion dollars in the Habitable World Observatory over the next two decades. This sounds like common sense, but common sense is not always common in academia. A popular misconception is that interstellar travel requires advanced technologies. But a simple calculation that I posted here with my Harvard College student Shokhruz Kakharov, shows that our own Voyager spacecraft will reach the opposite side of the Milky-Way galaxy relative to the Sun in about a billion years. Given that most stars formed billions of years before the Sun, there was plenty of time for extraterrestrial artifacts to reach our backyard, even if aliens used the 1970s technologies that we exployed to launch the Voyager spacecraft to interstellar space. What data does the U.S. government store in its classified archives? We do not know. But two weeks ago, former President Obama and current President Trump referred to UAP as real and potentially linked them to aliens. I was delighted to read the following statement of President Trump here: “Based on the tremendous interest shown, I will be directing the Secretary of War and other relevant departments and agencies to begin the process of identifying and releasing government files related to alien and extraterrestrial life, unidentified aerial phenomena (UAP), unidentified flying objects (UFOs), and any and all other information connected to these highly complex but extremely interesting and important matters. GOD BLESS AMERICA!”. The `Achilles Heel’ of past imagery and video data on UFOs or UAP, such as that presented in UAP congressional hearings over the past four years, is the unknown distances between the moving UAP and the moving cameras that recorded them. A nearby object might appear to move fast across the field of view even though its actual speed is modest. Knowing the time-dependent distances between multiple cameras and the object allows to infer its three-dimensional velocity and acceleration. It is possible that undisclosed data from U.S. Government satellites allows to infer the velocity and acceleration of UAP relative to the ground, as indicated in 2021 here by John Ratclife — the current CIA director. I would be delighted to participate in a review board that analyzes any such data and reports back to President Trump about its implications. The scientific research agenda of the Galileo Project is complementary to that of the Pentagon or the U.S. intelligence agencies. Whereas theses agencies focus on human-made objects for the purpose of protecting national security, the Galileo research team is focused on non-human-made objects. I told the five new postdocs who joined the Galileo research team this spring that they should feel free to wake me up in the middle of the night if they detect a UAP which clearly deviates from the performance envelope of human-made objects. Even if the Galileo research team does not find evidence for any extraterrestrial artifact, I will gladly share all lessons learned about the Galileo hardware, software and data with the Pentagon and the intelligence agencies, to help their mission in protecting national security. However, if we do find evidence for an extraterrestrial artifact, mark my words: I will not waste any time in attending cocktail parties with the Nobel committee members in Stockholm but rather play the Bob Dylan card in ignoring the phone call from this committee. My time will be better spent in finding more details about our extraterrestrial visitors. ABOUT THE AUTHOR (Image Credit: Chris Michel, National Academy of Sciences, 2023)Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. The paperback edition of his new book, titled “Interstellar”, was published in August 2024. Professional website: https://lweb.cfa.harvard.edu/~loeb/ Social media: https://avi-loeb.medium.com/ https://www.youtube.com/@ProfessorAviLoeb https://open.spotify.com/show/1zhndXkvSY2b8FdjspFpCd https://x.com/ProfAviLoeb View the full article

An image of the interstellar object 3I/ATLAS, taken from a distance of 66 million kilometers on November 6, 2025, by the JANUS camera onboard ESA’s Juice mission to Jupiter. The direction of the Sun is indicated on the top left by a yellow arrow pointing straight down. The blue arrow marks the direction of motion of 3I/ATLAS, along the 7 o’clock direction. The inset displays concentric brightness contours around the nucleus. (Image credit: ESA/Juice/JANUS)The European Space Agency (ESA) just released here a new image of the interstellar object 3I/ATLAS, obtained by the JANUS camera onboard the Jupiter Icy Moons Explorer (Juice) spacecraft. JANUS is a multicolor optical camera designed to take high-resolution photos of Jupiter and its icy moons. The image was taken on November 6, 2025, a week after closest approach of 3I/ATLAS to the Sun. It displays jets coming out of the nucleus of 3I/ATLAS opposite to the direction of the Sun. This is surprising since pockets of ice on the surface of a rock are supposed to be warmed up by sunlight on the Sun-facing side, creating jets that are initially directed at the Sun. The JANUS image resembles images taken by amateur astronomers from Earth around the same time, as I reported here, here, here and here. The JANUS camera took this image from a distance of 66 million kilometers, about 172 times the Earth-Moon separation. Throughout the month of November 2025, the Juice spacecraft used five of its science instruments to observe 3I/ATLAS, namely: JANUS, MAJIS, SWI, PEP and UVS. During the months that followed these observations, the Juice spacecraft was on the opposite side of the Sun relative to Earth. As a result, it was using its main high-gain antenna as a heat shield and its smaller medium-gain antenna to send back data to Earth at a slower rate. The related analysis teams had to wait until last week to receive the full extent of the collected data. In total, JANUS took more than 120 images of 3I/ATLAS, whereas the MAJIS, UVS and SWI obtained spectroscopic data regarding the composition of the gas plume around 3I/ATLAS, and PEP provided particle-collection data. Juice’s navigation camera also photographed 3I/ATLAS, and the analysis of that data is expected to be publicly released within a month. Recent images from the Hubble Space Telescope (archived here) implied that the diameter of the nucleus of 3I/ATLAS is 2.6 kilometers (as reported here), much bigger than the interstellar objects 1I/`Oumuamua and 2I/Borisov. The Juice spacecraft is expected to arrive at Jupiter in July 2031, where it will study Jupiter’s icy moons: Ganymede, Callisto, and Europa. However, 3I/ATLAS will arrive within 53.6 million kilometers from Jupiter as soon as March 16, 2026, as a result of its higher speed. When 3I/ATLAS will arrive closest to Jupiter, NASA’s Juno spacecraft will be able to observe it with all its instruments (listed here), including its low-frequency radio antenna. Half a year ago, I led a paper, posted here, which demonstrated that Juno could have intercepted the path of 3I/ATLAS if it still had most of the fuel that it started with. Congresswoman Anna Paulina Luna echoed this opportunity in an official letter that she posted online, as reported here. A crash of Juno on 3I/ATLAS could have given us a clear close-up view of this interstellar visitor a few seconds before impact. As I told a reporter today, it does not make sense for us to chase after 3I/ATLAS with a new expensive mission at this time (as contemplated here). The situation is similar to visiting a bar and noticing an interesting person. However, by the time you leave your chair — that person left the bar and you realize that a chase down the street would require a huge effort. Under these circumstances, it makes most sense to look around for other interesting person rather than to obsess about the missed opportunity. For the same reason, our best strategy following our recent encounter with the anomalies of 3I/ATLAS (as listed here plus here) would be to wait patiently for a future opportunity of an interception mission with another interesting interstellar visitor. We will likely discover hundreds of interstellar objects this century with the Rubin observatory monitoring the southern sky and the Argus array monitoring the northern sky. If one of the future interstellar objects will maneuver towards Earth without any effort required on our behalf to reach it, this particular visitor will rank at the highest alert priority of 10 on the Loeb Classification Scale (as quantified here, here and here). The alarming question, as with any blind date, would be whether this dating partner is proactive because it is friendly or because it is hostile. Time will tell. ABOUT THE AUTHOR (Image Credit: Chris Michel, National Academy of Sciences, 2023)Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. The paperback edition of his new book, titled “Interstellar”, was published in August 2024. Professional website: https://lweb.cfa.harvard.edu/~loeb/ Social media: https://avi-loeb.medium.com/ https://www.youtube.com/@ProfessorAviLoeb https://open.spotify.com/show/1zhndXkvSY2b8FdjspFpCd https://x.com/ProfAviLoeb View the full article

(Image credit: Greg Wyatt)Humans arrived at the cosmic stage relatively late, in the last 0.01 percent of cosmic history. We are not at the center of stage, since we reside on planet Earth which orbits the Sun and the Sun orbits the center of the Milky-Way galaxy, which is one out of a trillion galaxies in the observable Universe. Given that we arrived late and we are not featured centerstage, the cosmic play is not about us. Yet, we can still ask how we got here. The cosmic play started in the Big Bang, 13.8 billion years ago. We can only trace our roots out to the distance travelled by light since then. This sets the finite size of the cosmic stage which is visible to us, and we do not know what lies beyond its horizon. (Image credit: Greg Wyatt)On that stage, the initial conditions were remarkably synchronized to a part in 100,000. During the first 50,000 years of cosmic history, the mass budget was dominated by radiation. Subsequently, as the radiation cooled matter dominated, and small inhomogeneities in the matter distribution started growing gravitationally. The cosmic expansion of regions that were slightly denser than average was slowed down by self-gravity, leading ultimately for their turnaround and collapse into bound objects. The Milky-Way galaxy was one of these bound regions. The first generation of galaxies formed 50 million years after the Big Bang. Inside of them, gas cooled and condensed to make the first stars out of the primordial hydrogen and helium left over from the hot Big Bang. These stars were much more massive than the Sun, as cooling into smaller fragments was inefficient without heavy elements. The first heavy elements were synthesized inside these early fusion reactors. Within a few million years, the first massive stars exploded as supernovae and enriched their surroundings with the elements that enable life-as-we-know-it, such as the oxygen in water molecules or the carbon in organic molecules. (Image credit: Greg Wyatt)Subsequent generations of stars enriched the interstellar medium further and eventually led to the formation of metal-rich stars like the Sun in the last third of cosmic history. The Sun formed 4.6 billion years ago. Inside the debris disk that was left from its formation process — dust particles settled to the disk midplane where they coagulated to make bigger and bigger rocks. These so-called planetesimals eventually grew in size to make rocky planets. One of these planets — the Earth — resided in the so-called habitable zone where liquid water could flow on its surface owing to atmospheric pressure. (Image credit: Greg Wyatt)An early collision of Earth with a Mars-sized impactor birthed the Moon which stabilized the spin of Earth. As the Moon receded, its growing orbit reduced Earth’s spin and the duration of a day grew from 4 hours to 24 hours. The soup of chemicals on Earth enabled the emergence of primitive life in the form of the Last Universal Common Ancestor (LUCA) 4.2 billion years ago. Complex life, in the form of early eukaryotes, appeared on Earth around 2.1 to 2.9 billion years ago, during the Earth’s midlife, roughly when Mars lost its atmosphere and surface liquid water to become a desert. Humans emerged only in the last few million years. This cosmic history should teach us humility. We are minor actors on the cosmic stage and we exist because of everything that preceded us. Terrestrial life is fragile and could disappear once the delicate conditions enabling it will disappear as they did on Mars. Nobody would mourn the loss of humanity unless we make sure that our descendants travel to the stars where the history books are being written by the most accomplished cosmic survivors. *** In this essay, I featured four amazing watercolors from a series created by the celebrated artist, Greg Wyatt. These watercolors incorporate inspiring statements by Marcus Tullius Cicero, John Milton and Cervantes. This is the third in a sequence of essays, where Greg and I collaborate on the interface between art and science. The first essay in this series, titled “Music of the Cosmic Spheres,” appeared here; the second essay, titled: “Cosmic Waterfalls in Spacetime Cliffs,” appeared here; and the third titled “Missing Elements in the Cosmic Jigsaw Puzzle,” appeared here. ABOUT THE AUTHOR (Image Credit: Chris Michel, National Academy of Sciences, 2023)Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. The paperback edition of his new book, titled “Interstellar”, was published in August 2024. Professional website: https://lweb.cfa.harvard.edu/~loeb/ Social media: https://avi-loeb.medium.com/ https://www.youtube.com/@ProfessorAviLoeb https://open.spotify.com/show/1zhndXkvSY2b8FdjspFpCd https://x.com/ProfAviLoeb View the full article

(Image credit: Skeptic Magazine)One way to look at the practice of physics is as a way to develop constraints on our imagination. There is an infinite number of possibilities for what the physical reality might be, but only a tiny minority of these possibilities is realized in nature. To find out which possibilities are real, physicists collect quantitative data from instruments. Theorists imagine possibilities and experimentalists narrow them down based on data. This resembles the work of a detective, faced with a mysterious crime scene. The limits imposed on our best imagined possibilities do not bring us pleasure, so humans tend to circumvent these constraints by attending to more pleasing virtual realities. This could be done by attending a science-fiction movie, subscribing to belief cults on social-media, using metaverse goggles or taking recreational drugs. These virtual realities bend constraints at will and give rise to a pleasing experience that makes us happy. The raw physical reality that we all share in the absence of these agents, is under no obligation to make us happy. However, realism offers great benefits. One could think about the dialogue of an experimental physicist with nature as a relationship. The longest-lasting relationships are those which are based on factual details about the partners rather than on wishful thinking. We could imagine the existence of extra dimensions and reward string theorists for their mathematical virtuosity, but based on all experimental data so far — there are only three spatial dimensions and one time dimension. Without evidence to support string theory, it remains a speculative theoretical framework that might not describe how quantum mechanics and gravity are truly unified in reality. Yet, this unverified speculation was embraced by the mainstream of theoretical physics for half a century. This experience demonstrates that scientists can impress each other for a long time by constructing beautiful sandcastles. This is the case even though scientists may never use these imagined castles if they are washed out over time by the lack of experimental support. The risk of having the wrong idea about the physical reality without testing it for fifty years, is large. Only the guillotine of experiments can chop the head of wrong ideas and save us from pursuing ghosts. Popularity is not a good substitute for empirical tests in figuring out scientific truth. We all know about prisoners who were sentenced to death and while awaiting execution — DNA evidence exonerated them. The first case involved the Marine discus champion Kirk Bloodsworth in 1993, who was sentenced to death in Maryland for a 1984 rape-murder crime he did not commit (as detailed here). As of late 2024, at least 34 people have been exonerated from death row through DNA testing. Apparently, eyewitness testimonies — often used in our judicial system, were not sufficient to arrive at the truth in these cases. For that reason, science records data from instruments which are less susceptible to wishful thinking or a biased agenda than the human mind. The use of AI agents in future scientific research could improve the efficiency of data analysis. However, it must be cross-checked through experimental tests in order to verify whether its conclusions are reliable. Yesterday, I was asked whether 3I/ATLAS will pass within 8.11 thousand kilometers from Jupiter’s moon Ganymede, because multiple AI systems were forecasting that based on an essay which suggested that half a year ago. I replied that 3I/ATLAS will not get closer than 53.6 million kilometers from Jupiter whereas Ganymede orbital radius around Jupiter is only 1.07 million kilometers. Whoever fooled the AI systems to give the wrong message was wrong by a factor of 6,500. And when I pointed to the AI systems that they made a mistake, they tried to find their way out of admitting that they spread misinformation by suggesting that they were correct if 3I/ATLAS would have maneuvered significantly and entered a bound orbit around Jupiter. This brings me to the topic of Unidentified Anomalous Phenomena (UAP), where there is a huge culture of unverified claims and wishful thinking. Today, I had a podcast debate on UnHerd with the skeptic Michael Shermer, following my recent publication there (available here). Michael and I have a long-term bet (listed here), that: “Discovery or disclosure of alien visitation to Earth in the form of UFOs, UAPs, or any other technological artifact or alien biological form, as confirmed by major scientific institutions and government agencies, will not happen by December 31, 2030.” My rationale is as follows: “The search for technological artifacts has just started in earnest in 2025 with the discovery of the anomalous interstellar object 3I/ATLAS, the launch of the Rubin Observatory and the construction of three Galileo Project Observatories. Given that there are billions of Earth-Sun analogs in the Milky-Way galaxy — most of which are billions of years older than the solar system, and that it will take less than a billion years for our Voyager spacecraft to cross the Milky-Way disk, we must engage in the scientific search for extraterrestrial technological artifacts. It is better to be an optimist because life is sometimes a self-fulfilling prophecy. This is why I am engaged in the search with the hope that we will find a partner on our blind date with interstellar objects.” This bet is timely. Last week, former President Obama said about aliens: “They’re real but I haven’t seen them.” Following that, President Trump released the statement: “Based on the tremendous interest shown, I will be directing the Secretary of War and other relevant departments and agencies to begin the process of identifying and releasing government files related to alien and extraterrestrial life, unidentified aerial phenomena (UAP), unidentified flying objects (UFOs), and any and all other information connected to these highly complex but extremely interesting and important matters. GOD BLESS AMERICA!” The disclosure of related information will be wonderful news for scientists, as long as it contains quantitative data in the form of imagery or materials that can be studied by scientists. Blocking the dissemination of such data is contrary to the spirit of science which relies on independent vetting by multiple researchers. Our imagination can come up with multiple possibilities: perhaps UAP are artifacts from an old civilization that predated us on Earth or perhaps we have addressed Enrico Fermi’s 75-year-old question regarding interstellar visitors: “Where is everybody?” with the answer: “Right here.” But just as in the case of string theorists or prisoners on death row — the only way to make progress and separate figments of our imagination from reality is by studying the evidence directly. We could be intrigued by UAP eyewitness testimonies but should not rely on them. It is possible that evidence is scarce but there is no doubt that any real evidence is diluted by a flood of bullshit and misinformation. To separate the “wheat” from the “chaff”, we must examine directly what we are holding in our hands. Many scientists ignore the UAP reports. The SETI community banned any UAP discussions in its conferences. This reflects an anti-scientific sentiment, stemming from an echo chamber of prejudice. To foster clarity on UAP, we should not ignore them but instead bring the scientific study of UAP to the mainstream of physics — where experimental data will promote new knowledge. This is the rationale behind the Galileo Project under my leadership, of which Michael Shermer is an affiliate. Irrespective of what is discovered about UAP by 2030, Michael and I agreed to donate the money in our long-term bet towards the Galileo Project’s research, as we both believe in evidence-based science as the best guide to new anomaly-driven knowledge. I have one advantage relative to Michael on this front as I am a practicing scientist aiming to collect this evidence, so I can actively promote my chances for winning the bet with him. If and when new information from the Pentagon or the U.S. intelligence agencies will be shared with scientists like myself, I will be delighted to work on its interpretation and analysis. We live in an exciting time, when we have the scientific tools needed to figure out whether we are being visited by extraterrestrials. I surely hope we are. Such a visit could suppress our terrestrial disputes, in the same way that a visit by a neighbor stops family members from engaging in a loud argument. I do not only talk the talk but also walk the walk. On Thursday, February 26, 2026 at 11AM New-York time, I will discuss findings from my scientific search for extraterrestrials, streamed live on YouTube at the following link: https://medium.com/media/b156bb4e3b3ec4a90183d0c55f1aee04/hrefCheck it out. ABOUT THE AUTHOR (Image Credit: Chris Michel, National Academy of Sciences, 2023)Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. The paperback edition of his new book, titled “Interstellar”, was published in August 2024. View the full article

(Image credit: Galileo Project)Exciting news: the Galileo Project is seeking help from volunteers in labeling objects in the sky! The Galileo Project’s goal is to conduct a systematic scientific search for evidence regarding extraterrestrial technological artifacts. Our research team aims to bring the search for extraterrestrial technological signatures of extraterrestrial technological civilizations from accidental or anecdotal observations to the mainstream of transparent, validated and systematic scientific research. The Galileo Project is complementary to traditional SETI, in that it searches for physical objects near Earth that are associated with extraterrestrial technological equipment, and not for electromagnetic signals from distant stars. (Image credit: Galileo Project)The Galileo Project, headquartered at Harvard University under my leadership, operates three new observatories: one in Massachusetts, another in Pennsylvania and the latest and most advanced — in Nevada. In difference from common astronomical observatories which seek distant sources, the architecture of the Galileo observatories was designed to focus on objects within the Earth’s atmosphere. Our instruments observe continuously the entire sky at each location in the infrared, optical, radio and audio bands. The data stream is being analyzed by artificial intelligence (AI) models in search for anomalous outliers among millions of documented objects every year. We search for Unidentified Anomalous Phenomena (UAP) with flight characteristics that deviate from human-made or natural objects. Our goal is to figure out the nature of UAP through detailed observations. Our observatories aim to infer distances of objects through the method of triangulation, by observing them from different directions with multiple units separated by about 10 kilometers from each other. (Image credit: Galileo Project)The classification of sources in the sky into familiar human-made objects — like airplanes, drones, helicopters, balloons or satellites, and familiar natural objects — like birds or clouds, is challenging because each of these objects appears differently depending on the time of the day, the background sky patterns, and its orientation relative to the Sun or the Moon. In the process of training our AI models, we are seeking help from volunteers who are interested in labeling objects from our latest images. For that purpose, the Galileo research team established a new website which displays images and asks interested volunteers to classify objects in the sky into known categories. If you are interested in helping out the Galileo Project in its exciting mission, please click on the link here. Home - Galileo Project Data Annotation Portal While our technology provides the framework, the success of the Galileo Project’s mission ultimately depends on human insight. This is where you come in. Our engineering and data teams are currently focused on infrastructure and model development, meaning that many of the images in our database have never been viewed by a human eye. This is your opportunity to see our data first-hand. By participating, you are directly engaging in the search for UAP. Indeed, there is a real possibility that you might spot something significant that has gone unnoticed. To ensure our machine learning models can accurately detect, track, and characterize UAP, they require a robust dataset of manually labeled images. We currently lack the internal capacity to label this volume of data alone. We are asking the community to assist us with this essential task to improve the accuracy and reliability of our detection systems. Last week, former President Obama and current President Trump discussed UAP. Obama said about aliens: “They’re real but I haven’t seen them,” President Trump responded that Obama gave “classified information, he is not supposed to be doing that.” Shortly afterwards, President Trump released the statement: “Based on the tremendous interest shown, I will be directing the Secretary of War and other relevant departments and agencies to begin the process of identifying and releasing government files related to alien and extraterrestrial life, unidentified aerial phenomena (UAP), unidentified flying objects (UFOs), and any and all other information connected to these highly complex but extremely interesting and important matters. GOD BLESS AMERICA!” Of course, we can all wait for the Pentagon or relevant departments in the intelligence agencies to release information about UAP, but while waiting — we can also search the sky for rare and exotic objects. We do not need to rely on government for data on objects manufactured by non-human intelligence. We can simply look up. It took the research team of the Galileo Project nearly 5 years to construct three Galileo observatories. Now that these observatories deliver fresh data, we need your help in sorting out objects in our images. All of us can search for “alien and extraterrestrial life, unidentified aerial phenomena (UAP), unidentified flying objects (UFOs), and any and all other information connected to these highly complex but extremely interesting and important matters.” (Image credit: Alex Delacroix, Galileo Project)ABOUT THE AUTHOR (Image Credit: Chris Michel, National Academy of Sciences, 2023)Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. The paperback edition of his new book, titled “Interstellar”, was published in August 2024. Professional website: https://lweb.cfa.harvard.edu/~loeb/ Social media: https://avi-loeb.medium.com/ https://www.youtube.com/@ProfessorAviLoeb https://open.spotify.com/show/1zhndXkvSY2b8FdjspFpCd https://x.com/ProfAviLoeb View the full article

(Image credit: White House)https://medium.com/media/05c48d4023f33d5a599ad983bfbf158c/hrefA couple of hours after I posted my latest video, President Trump released the following statement: “Based on the tremendous interest shown, I will be directing the Secretary of War and other relevant departments and agencies to begin the process of identifying and releasing government files related to alien and extraterrestrial life, unidentified aerial phenomena (UAP), unidentified flying objects (UFOs), and any and all other information connected to these highly complex but extremely interesting and important matters. GOD BLESS AMERICA!” Following this statement, I was invited to participate in 18 television interviews in a single day, including one from Washington, DC. Below are some of the key points I made during those interviews. Only mediocre scientists are dogmatic about UAP. Curious scientists are humbled by what we do not understand. We do not know what most of the matter in the universe is. We do not know what most of the energy in the universe is. We call them dark matter and dark energy. We also do not know whether we are alone. Given the vast expanse of cosmic space and time, it was presumptuous for Enrico Fermi to ask, “Where is everybody?” over lunch in Los Alamos in 1950. When anomalies are documented by trustworthy intelligence officers and military personnel, mainstream scientists should be curious enough to investigate what those anomalies mean. So far, the public has not seen the most anomalous data. It remains classified and may include high-resolution satellite imagery or materials from alleged crash sites. Determining the nature of that evidence is extremely important for national security. It could indicate technological developments by adversarial nations. Even if that turns out not to be the case, studying the evidence is never a waste. It strengthens our ability to protect our nation. My hope is that the Congressional UAP task force led by the visionary Congresswoman Anna Paulina Luna will be able to review evidence that was previously held in secrecy. If detailed scientific analysis is needed, I am ready to assist. The images and videos released publicly so far are not of high scientific quality. Without precise distance measurements, it is difficult to determine velocities or accelerations. However, the underlying data may contain clues that scientists can analyze rigorously. For example, if materials were recovered from a crash site, it would be straightforward to test whether they originated beyond the solar system. Even a gram of material is sufficient for isotope analysis using a mass spectrometer. All materials in our solar system formed from the same reservoir. Material from another star would likely exhibit isotopic signatures shaped by a different stellar environment. Science can help the government and Congress determine whether any evidence collected over the past century may be of interstellar origin. My interest focuses on nonhuman intelligence and technological products from civilizations beyond the solar system. Intelligence agencies and the Pentagon focus on human-made technologies. Our interests are complementary. If they encounter something outside their expertise, I would be glad to help. The primary challenge is how to declassify information without compromising national security. One approach is time. Information from 50 years ago is unlikely to be relevant to today’s battlefield technologies. Human-made systems have advanced dramatically. Another possibility is to release data on objects whose behavior lies outside the envelope of known human technologies. If an object clearly exceeds those limits, it is unlikely to be tied to terrestrial geopolitics. In that case, it would be a matter for scientific inquiry rather than national security. It is arrogant to assume we are at the top of the cosmic food chain in the Milky Way. If there is a smarter civilization in our cosmic neighborhood, we should learn from it. If we discovered evidence that a neighbor threw a tennis ball into our backyard, we would not hide it from our family. Similarly, humanity deserves to know if we have a cosmic neighbor. In fact, many people reading the daily news might welcome the idea that a more advanced civilization exists, one that could serve as a better role model than our current family members. “Are we alone?” is perhaps the most romantic question in science. Answering it would allow us to form a deeper emotional connection with the universe, transforming it from a cold, lonely expanse of matter and radiation into something inhabited. If presented with a fragment of a spacecraft recovered from a crash site, the first step would be to analyze its composition and determine whether the material originated beyond the solar system. The second step would be to study its structure to see whether it represents technology or science beyond our own. If there is a more advanced civilization in our cosmic neighborhood, this would be an opportunity to learn and advance. We are living at the beginning of an exciting era. There is a race unfolding between artificial intelligence, which is itself an alien form of intelligence made of silicon rather than flesh and blood, and the possibility of discovering extraterrestrial intelligence from another star. Which will we encounter first? Without searching, we will not find out. I am excited to be alive at this moment and to be part of that search. ABOUT THE AUTHOR (Image Credit: Chris Michel, National Academy of Sciences, 2023)Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. The paperback edition of his new book, titled “Interstellar”, was published in August 2024. Professional website: https://lweb.cfa.harvard.edu/~loeb/ Social media: https://avi-loeb.medium.com/ https://www.youtube.com/@ProfessorAviLoeb https://open.spotify.com/show/1zhndXkvSY2b8FdjspFpCd https://x.com/ProfAviLoeb View the full article

The Fox News reporter Peter Doocy asked President Trump (left) and Avi Loeb (right) about aliens. (Image Credits: Fox News)Below is the transcript of a new short video that I just released on my YouTube Channel here. *** A few hours ago, on Thursday, February 19, 2026, President Trump was asked an interesting question by Fox News reporter Peter Doocy. The question followed comments that had received significant attention this week after former President Barack Obama said that aliens are real. President Trump was asked whether he had seen any evidence of nonhuman visitors to Earth. In response, President Trump said that Obama had revealed classified information and was not supposed to be discussing it. He added that he did not personally have an opinion on whether aliens are real, though many people believe they are. I spoke with Peter Doocy a few months ago about this same question, and I would like to comment on what we just heard from President Trump. Much of the data concerning unusual objects in the sky is classified, and there are understandable reasons for that. First, the data is often collected by highly sophisticated, classified sensors. The United States does not want adversarial nations to understand the quality and capabilities of those systems. For example, high-resolution government satellites may capture anomalous objects, but the performance of those satellites cannot be publicly revealed. Second, if intelligence officers are studying materials or images they cannot identify, they may prefer to keep that information classified. If such objects were manufactured by adversarial nations, revealing details could expose vulnerabilities in U.S. defense systems. No nation wants to advertise weaknesses in its detection or response capabilities. There is also a bureaucratic dimension. Administrators in intelligence agencies may not want to publicly acknowledge that there are objects they cannot identify, especially given the large budgets allocated for national security. Classification limits the number of people who can review the data, including members of Congress. For all these reasons, it makes sense that such information remains classified. At the same time, the president is aware of many incidents in which intelligence personnel and military officers encounter unusual objects whose origins they cannot determine. One possibility is that these are technological systems developed by other nations, which would be a serious national security concern. But because the data is classified, the broader public does not have access to the evidence. When President Obama spoke about unidentified objects, that information may well have been classified. However, it does not rule out the possibility that some of these objects could represent extraterrestrial technologies. To determine their origin, we need better data. In most cases, that better data simply does not exist. The simplest approach is to set the issue aside until better evidence becomes available. That is precisely why I am leading the Galileo Project. I am not interested in technologies manufactured by humans on Earth. The history of terrestrial technology does not interest me. I am far more curious about whether a more advanced civilization exists in interstellar space. The Galileo Project is designed to search for objects that operate outside the envelope of known human technologies. We have built three observatories — in Massachusetts, Pennsylvania, and Nevada — and we are collecting data on millions of objects. We are searching for outliers that cannot be explained as human-made systems. If we find evidence of advanced human-made technologies, I will gladly share that information with the Pentagon. Even if we do not find extraterrestrial technology, the sensors and artificial intelligence tools we developed could benefit national security. As an American citizen, I would be pleased if our work strengthens national defense. However, my primary interest is extraterrestrial technology. The Pentagon focuses on human-made systems. Our interests are complementary, not overlapping. If we discover something unusual, it could either improve national security or advance one of the most profound scientific questions: Are we alone? One step that can be taken immediately is to declassify events from 50 years ago. Technologies used half a century ago are no longer strategically sensitive. Releasing older data could significantly advance scientific research. I would be delighted to help the government analyze declassified incidents. I would also welcome collaboration with the White House on any future declassifications. If additional details about anomalous objects become available, I would be happy to assist in interpreting them. ABOUT THE AUTHOR (Image Credit: Chris Michel, National Academy of Sciences, 2023)Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. The paperback edition of his new book, titled “Interstellar”, was published in August 2024. Professional website: https://lweb.cfa.harvard.edu/~loeb/ Social media: https://avi-loeb.medium.com/ https://www.youtube.com/@ProfessorAviLoeb https://open.spotify.com/show/1zhndXkvSY2b8FdjspFpCd https://x.com/ProfAviLoeb View the full article

A symmetric structure of three equally-separated jets is apparent near the nucleus of 3I/ATLAS, after applying the Larson-Sekanina rotational gradient filter to two exposures by the Hubble Space Telescope on 2025–12–27 UT. Two of the jets, separated by about 120 degrees, are prominent in both images, but their structure broadens into a wider fan on the right panel. Such morphological changes modulate the amplitude of the brightness variability. (Image Credit: T. Scarmato and A. Loeb 2026)In a new paper (accessible here) that I co-authored with the Italian observer Toni Scarmato, we use images from the Hubble Space Telescope to study the motion of the symmetric system of three jets around the nucleus of the interstellar object 3I/ATLAS. The Hubble images were processed through a Larson–Sekanina rotational-gradient filter -which removed the circularly symmetric glow around the nucleus. The remaining brightness map shows three close-in jets in addition to a sunward anti-tail on a much larger scale, as discussed in our previous paper here. These post-perihelion Hubble Images were taken between November 30 and December 27, 2025. The most prominent jet among the three is directed opposite to the Sun and appears to wobble over a period of 7.20 (± 0.05) hours. The total brightness shows contemporaneous variability with a period of 7.136 (±0.001) hours and an amplitude of about 30%. We interpret the characteristic post-perihelion period of about 7.1 hours as an attitude precession or nutation associated with a misalignment of the rotation axis with the symmetry axes of the nucleus. The wobble around the rotation axis displays a characteristic angular excursion of order 20 degrees, while the rotation axis is aligned with the sunward direction to within 20 degrees. The right panel shows the schematic geometry of the 3-jet system near the nucleus of 3I/ATLAS (excluding the prominent anti-tail outflow towards the Sun), based on the filtered Hubble brightness map on the left. The projected spin axis in the sunward direction appears at a position angle of PA= 110 degrees, and the anti-sunward direction is at PA= 290 degrees. The PAs and oscillation half- amplitudes of the 3 jets are as follows: Jet 1: 55 (± 12.8) degrees; Jet 2 (sunward): 290 (± 20) degrees; Jet 3: 170 (± 12.6) degrees. The anti-sunward jet at PA=290 degrees wobbles with period of 7.2 hours. (Image Credit: T. Scarmato and A. Loeb 2026)Based on the inferred diameter of 2.6 kilometers for the nucleus of 3I/ATLAS (as reported here), only about a percent of the brightness of 3I/ATLAS originates from the reflection of sunlight by its nucleus. When rotation is misaligned with the symmetry axes of the nucleus, it can produce quasi-periodic wobbles and a non-sinusoidal variability. The new analysis links the inferred 7.1-hour period to an attitude precession or nutation of the multi-jet system. The brightness variability tracks transitions between collimated and fan-like morphologies of the jets. The phase-folded light curve of 3I/ATLAS shows a period of about 7.14 hours. (Image Credit: T. Scarmato and A. Loeb 2026)Whereas the position angle of the most prominent jet shows variability with a period of 7.20 (± 0.05) hours, shorter periods are also apparent. Jets 2 shows a period of 2.9 hours and Jet 3 shows a period of 4.3 hours. The sum of 2.9 plus 4.3 is 7.2 hours. The phase-folded variability of the position angle of Jet 2 shows a period of about 2.9 hours. (Image Credit: T. Scarmato and A. Loeb 2026)The phase-folded variability of the position angle of Jet 3 shows a period of 4.3 hours. (Image Credit: T. Scarmato and A. Loeb 2026)Summary of the inferred periods in the wobble of the jet system around 3I/ATLAS. (Image Credit: T. Scarmato and A. Loeb 2026)We interpret the ~7.1-hour periodicity as the result of the rotation of 3I/ATLAS being misaligned with the principal symmetry axes of its nucleus. The jet structure undergoes a quasi-periodic wobble as the nucleus exhibits precession and nutation about the rotation axis. This interpretation explains the orientation oscillations of the jets with morphology-dependent amplitudes and phases, the non-sinusoidal variability, and the sensitivity of the lightcurve to evolving collimation (fan opening) of the jets. Multiple jets in different directions tend to balance each other and stabilize the rotation of 3I/ATLAS. Jet 2 — which is oriented approximately opposite to the Sun and close to the projected rotation axis — anchors the large-scale geometry, whereas Jets 1 and 3 trace the precession cone through their position angle oscillations. The wobble and changing collimation of the jets modulates both the projected jet directions and the total brightness. The fundamental question that remains unresolved is whether the symmetric triple-jet system is a signature of technological thrusters or the sublimation of natural pockets of ice on the surface of a natural rocky iceberg. ABOUT THE AUTHOR (Image Credit: Chris Michel, National Academy of Sciences, 2023)Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. The paperback edition of his new book, titled “Interstellar”, was published in August 2024. Professional website: https://lweb.cfa.harvard.edu/~loeb/ Social media: https://avi-loeb.medium.com/ https://www.youtube.com/@ProfessorAviLoeb https://open.spotify.com/show/1zhndXkvSY2b8FdjspFpCd https://x.com/ProfAviLoeb View the full article

(Image Credit: Loeb image collection)In an early-morning research discussion with my colleague, Liam Connors, I noted that I have 11 interviews today. Liam wondered: “you have so many interviews with prospective PhD students?” and I explained: “no, these are interviews with television outlets in the US, Italy, Spain and Israel, a newspaper in the UK and half a dozen, hour-long podcasts.” Just the beginning of another busy day after my morning jog at sunrise. Yet, I remained optimistic about my tight itinerary. Every simple beginning holds the promise of a grand finale. Consider our Universe as a role model. Our vast cosmos gave birth to intelligence after 13.8 billion years of cosmic history which began in a simple Big Bang. This magnificent outcome was a direct consequence of the laws of physics acting on a set of simple conditions, initiated when the Universe was a fraction of a second old. The statistical initial conditions can be summarized on a single sheet of paper, spanning about 5 kilobytes of information. Yet, our AI systems train now on hundreds of zettabytes in the world’s digital information. To maintain the appropriate perspective of cosmic modesty, we must keep in mind that there are of order ten billion Earth-like planets around Sun-like stars in the Milky-Way galaxy alone, and of order a trillion similar galaxies in the observable volume of the Universe. Based on the isotropy of the microwave background fluctuations, we infer that similar conditions continue out to a scale which is at least 4,000 larger than our cosmic horizon (as discussed here). All in all, this implies an information content beyond 10^{21}*10^{10}*10^{12}*(4,000)³= 6.4x10^{53} bytes, a factor of 10^{50} larger than the statistical information encoded in the initial conditions from the Big Bang. This complexity of details is a direct result of the primordial initial conditions and the laws of physics, as is routinely demonstrated by cosmological simulations. According to our current scientific understanding, quantum fluctuations in the early Universe translated to density inhomogeneities of matter and radiation, which grew gravitationally to make bound objects like the Milky-Way galaxy, inside of which gas cools and fragmented into stars like the Sun, next to which the debris of dust particles coagulated to make planets like the Earth, on the surface of which the chemistry of life in liquid water created biological brains which eventually became smart enough to create artificial intelligence. In short, the complexity we find in our world today is a natural consequence of gravity and the nearly-smooth primordial Universe. The initial conditions were statistically uniform within our cosmic horizon, yet they resulted in people with very different personalities on Earth as a result of complex circumstances and interactions with numerous coincidental details. Why was the early Universe so simple? Perhaps because any earlier “wrinkles” in spacetime were smoothed out and diluted by “a cosmic iron” in the form of an accelerated expansion such as cosmic inflation. If cosmic inflation took place, we will never know what preceded it because inflation diluted the earlier information and left behind a set of simple initial conditions for the subsequent cosmic history. Changing the composition or quantum fluctuation spectrum of the early Universe would have resulted in very different outcomes. If such outcomes had materialized without leading to intelligence, there would have been no brains in the cosmos the appreciate it. In our Universe, fluctuations started to grow when matter began to dominate over radiation. If we were to sample a spherical volume within the early matter-dominated Universe, we would have noticed that it has a nearly zero net energy because the negative gravitational binding energy of matter would have been nearly balanced by the positive kinetic energy associated with cosmic expansion. This insight has two major implications. First, a small enhancement in density makes a region — like the one that created the Milky-Way — gravitationally bound and drives it towards collapse. Second, to initiate such a Universe, a quantum-gravity engineer does not need to invest any energy. We do not know how to create a baby Universe in the laboratory. How to do so would be the first question that I would love to ask an alien scientist. If they figured out the recipe for a baby Universe like the recipe for a cake, including the ingredients and the instructions for how to put them together, then my follow-up question would be: “do you have the oven needed to bake this cake?” Most likely, such an oven needs to reach a very high temperature, of order the Planck temperature — corresponding to 10^{32} degrees Kelvin, so even the most advanced alien scientists in our cosmic neighborhood might not have it. But it is still possible that our Universe emerged from an oven created by a higher-level being outside our cosmic horizon. Whether that is the case, we might never know. The training data set of all siblings in our family of intelligent civilizations is limited to the same cosmic horizon and so our alien dating partners might not have further insights on this question. When physics runs into a wall of the unknowable, metaphysics may come to the rescue. ABOUT THE AUTHOR (Image Credit: Chris Michel, National Academy of Sciences, 2023)Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. The paperback edition of his new book, titled “Interstellar”, was published in August 2024. Professional website: https://lweb.cfa.harvard.edu/~loeb/ Social media: https://avi-loeb.medium.com/ https://www.youtube.com/@ProfessorAviLoeb https://open.spotify.com/show/1zhndXkvSY2b8FdjspFpCd https://x.com/ProfAviLoeb View the full article

A survey telescope’s detection captures a bright, actively outgassing interstellar object analogous to Wald’s detectable bombers, while numerous dark, inactive, or small ISOs pass undetected through the Solar System. The visible population represents only those objects that “survived” into our catalogs by meeting current detection thresholds. (Image Credit: O.Eldadi, G. Tenenbaum and A. Loeb)by Omer Eldadi (1), Gershon Tenenbaum (1) and Avi Loeb (2)Department of Psychology, Reichman University, Herzliya, IsraelDepartment of Astronomy, Harvard University, Cambridge, MA, USA(Submitted for publication as a perspective article in a peer-reviewed journal) Abstract The three known interstellar objects (ISOs): 1I/’Oumuamua, 2I/Borisov, and 3I/ATLAS, were each detected serendipitously by surveys designed for other purposes. Hubble Space Telescope observations confirm that even 3I/ATLAS, the brightest of the three, would have escaped detection without bright enhancement from its dust coma, while corrected nucleus measurements revise the inferred number density upward by an order of magnitude. We argue that the known sample is shaped not by a selection bias in which a researcher chooses a non-representative subset from an accessible population, but by survivorship bias: objects too small, too dark, too fast, or insufficiently active are structurally excluded from detection and leave no observational trace. We estimate that existing instruments prove less than ~0.1% of the plausible ISO parameter space across four independent axes of invisibility: size, albedo, velocity, and activity. The apparent diversity of the known three objects further activates the representativeness heuristic, creating an illusion of population coverage that compounds the statistical distortion. We conclude by outlining a multi-modal detection architecture designed to find that the object’s current infrastructure is structurally incapable of detecting. Introduction During the Second World War, the Statistical Research Group at Columbia University was tasked with a problem of immediate operational importance: where should armor be added to allied bombers to improve their survivability? Engineers had catalogued the distribution of bullet holes on aircraft returning from combat missions and proposed reinforcing the most heavily damaged areas: the fuselage, wings, and fuel systems1. The mathematician Abraham Wald recognized the critical flaw in this reasoning2. The damage distribution they observed came exclusively from aircraft that had survived; the areas showing no damage like the engines and cockpit, were precisely those where hits were fatal, because aircraft struck have never returned. The military was studying survivors, not the full population, and thus, their observations were only partially reliable. This insight, now known as survivorship bias3, has become a foundational concept in statistics, epidemiology, finance, and experimental design. We argue here that interstellar object (ISO) science faces an analogous and equally consequential form of this bias. Since the first confirmed ISO, 1I/‘Oumuamua, was detected in 20174,5, only two additional interstellar visitors have been identified: 2I/Borisov in 20196 and 3I/ATLAS in 20257. Yet all three were detected because they were large enough, bright enough, and close enough to the Sun, and sufficiently well-placed geometrically to be captured by surveys designed primarily for near-Earth object (NEO) detection. They are the “detectable bombers”. The objects that were too small, too dark, too fast, on unfavorable trajectories, or lacking outgassing activity, remain undetected. Individual authors have noted aspects of this detection incompleteness, including evidence that previous wide-field surveys missed numerous ISOs of comparable size to those already detected8, and that dark, non-reflective ISOs require entirely new detection modalities9,32. This Perspective proposes survivorship bias as a unifying framework for these detection limitations. Survivorship Bias — Not Selection Bias It is imperative to distinguish the bias we describe from conventional selection bias. Selection bias arises when a researcher, consciously or unconsciously, chooses a non-representative subset from an available population. For example, by preferentially studying bright galaxies in a catalog that also contains faint ones, or by recruiting only college-affiliated volunteers for a clinical trial. In such cases, the full population is in principle accessible; the distortion is introduced by the act of selection. The ISO detection problem is fundamentally different. We are not selecting a biased subset from a larger accessible catalog, but rather analyzing the entire available sample, every interstellar object ever detected, and that sample consists of three objects as of this writing. There is no drawer of neglected ISOs waiting to be included. The bias is not in our analysis of the data; it is in the data itself. Objects that were too dark, too small, too fast, or too poorly positioned were never registered by any instrument, never assigned a designation, and never entered any database. This is the defining structure of survivorship bias: the absence of the non-survivors is invisible precisely because they leave no trace. Just as Wald’s analysts could not study the bombers that never returned, because those aircraft and their crews were lost over enemy territory, we cannot study the ISOs that transited the Solar System without detection, because they left no observational residue (see Figure 1). This distinction carries methodological consequences. When facing selection bias, one corrects by improving sampling from a known population. When facing survivorship bias, the population itself is unknown, and correction requires expanding the conditions under which survival (here, detection), is possible. One cannot resample from a pool that does not exist, thus must build new instruments, open new wavelength windows, and develop new detection architectures so that objects which previously could not “survive” into our catalogs are finally able to do so. The solution is not better statistics applied to three objects. It is the creation of detection conditions under which the next three hundred objects include those that the current infrastructure is structurally incapable of finding. The Three Survivors: What We Know and How We Found Them The known ISO sample, while small, is already diverse and the circumstances of each detection are as revealing as the objects themselves. 1I/‘Oumuamua was detected by the Pan-STARRS1 survey on 19 October 2017, already past perihelion and outbound4. It displayed no detectable coma or outgassing yet exhibited an anomalous non-gravitational acceleration that remains without consensus explanation10. Its extreme aspect ratio exceeding 6:1, unlike any known Solar System body⁴. 1I/ʻOumuamua was discovered only because it passed within 0.16 AU of Earth. Had its trajectory differed by a small margin, it would have gone unnoticed entirely. 2I/Borisov was discovered on 30 August 2019 by amateur astronomer Gennadiy Borisov6. With a classic cometary coma and CO abundance exceeding 170% relative to H₂O11,12, it was the most compositionally familiar of the three ISOs, yet its volatile inventory pointed to formation in a carbon-rich environment unlike our own protoplanetary disk. Borisov survived into our catalogs precisely because it behaved like a comet; its activity made it bright enough for a 0.65-m amateur telescope to find. If the next five hundred interstellar detections resemble 1I/’Oumuamua, then it is 2I/Borisov (not ‘Oumuamua), that is the anomaly. The assumption that cometary activity constitutes the default state of interstellar matter may itself be an artifact of survivorship bias: we classify Borisov as ‘normal’ precisely because it resembles the objects our instruments were built to find. 3I/ATLAS which was detected on 1 July 2025 by the ATLAS survey at approximately 4.5 AU from the Sun7, proved the most massive and complex. Hubble Space Telescope (HST) observations constrained the nucleus radius to rn ≤ 2.8 km8 (an initial upper bound from early imaging); subsequent analysis extracted a refined estimate of rn = 1.3 ± 0.2 km15, yet revealed that the surrounding dust coma contributed the vast majority of observed brightness. The dust coma dominated the optical cross-section of 3I/ATLAS. Without it, the object would have gone undetected by ATLAS8. The object displayed sunward dust emission indicating anisotropic ejection from the dayside of the nucleus rather than a conventional radiation-pressure-shaped dust tail8. The James Webb Space Telescope (JWST) spectroscopy revealed a CO₂-dominated volatile inventory with anomalous nickel-to-iron ratios¹³, while polarimetric observations showed extreme negative polarization reaching −2.7% at 7° phase angle, unprecedented among known comets¹⁴. A critical observation unites these three detections: all were found serendipitously by wide-field surveys designed for other purposes. None was detected by a dedicated ISO search program. Moreover, all three exhibited properties that made them conspicuous: large effective cross-sections, relatively moderate interstellar velocities (26–68 km/s), and heliocentric distances within approximately 5 AU at discovery. The number density of objects with the scattering cross-section of 3I/ATLAS has been estimated as ~3 × 10⁻⁴ au⁻³ at first⁷, but this figure was based on a coma-contaminated absolute magnitude that substantially overestimated the nucleus size. Subsequent HST nucleus extraction yielded a true radius of rn = 1.3 ± 0.2 km six months later15, revising the number density upward by an order of magnitude to ~3 × 10⁻³ au⁻³ and implying that approximately one comparable object resides within 4.5 AU of the Sun at any given time15. Yet, HST observations confirm that 3I/ATLAS itself would have escaped detection without the brightness enhancement provided by its dust coma⁸. Previous surveys missed such objects because inactive nuclei lack the coma brightness that made 3I/ATLAS detectable⁸. This is survivorship bias in action: the properties of the detected ISOs reflect the detection threshold, not the intrinsic object population. The Representativeness Trap: How Cognitive Biases Compound Statistical Distortion A further cognitive dimension compounds the statistical problem, and it is this dimension that distinguishes our conceptual framework from purely astronomical discussions of completeness. The three known ISOs exhibit strikingly different properties: 1I/’Oumuamua was anomalously shaped and inert, 2I/Borisov was conventionally cometary, and 3I/ATLAS was chemically complex and massive. Such diversity activates what Kahneman and Tversky termed the representativeness heuristic — the tendency to judge a small sample as representative of the parent population when it displays internal variety16. The representativeness heuristic leads individuals to evaluate the probability that a sample belongs to (or represents) a population based on the degree to which it resembles the population’s expected features, rather than on the actual statistical properties of the sampling process16,17. Critically, Tversky and Kahneman demonstrated that people are systematically insensitive to sample size when evaluating the reliability of statistical results, expecting small samples to reproduce the properties of the parent population18. The related tendency to judge representativeness by surface resemblance rather than sampling logic16 suggests that a small sample displaying apparent variety may be treated as though it were a large, representative one. In the ISO context, the apparent coverage of “anomalous”, “normal”, and “complex” archetypes creates a compelling but illusory sense that the population has been adequately sampled. This heuristic has been documented extensively in scientific reasoning itself. Nickerson19 reviewed confirmation bias in science — the tendency to interpret new evidence as consistent with existing beliefs and noted that people are particularly susceptible to drawing premature conclusions, which are then reinforced by selective attention to supportive evidence. Greenwald20 demonstrated the consequences of prejudice against null results, showing how positive findings in small samples are outweighed relative to their evidential value. More recently, Ioannidis21 formalized conditions under which published research findings are likely to be false, with small sample size as a primary risk factor. Research on team cognition in expert groups has revealed that shared mental models, while facilitating coordination22, can also promote premature consensus and resistance to disconfirming evidence when teams operate under time pressure with limited data23. Three data points drawn exclusively from the detectable fraction of parameter space cannot constrain the properties of the undetectable majority, regardless of how different those three points appear from one another. The analogy is direct: if a marine biologist caught only three fish, all near the surface, all attracted to bait — the fact that they belonged to three different species would not justify conclusions about the deep ocean. Recognizing this heuristic trap is essential if the astronomical community is to resist premature closure on the nature of the interstellar population. Premature closure is not merely a theoretical concern. The rapid proliferation of formation and ejection models tailored to the properties of three objects24,25,26 suggests that the field may already be anchoring on a biased sample. Anchoring, the tendency to rely excessively on the first available information, is another well-documented cognitive bias27 that compounds representativeness. Once researchers invest intellectual effort in explaining the three known ISOs, the psychological cost of acknowledging that these objects may be atypical of the broader population rises, creating resistance to revision even in the face of null results from future surveys. People must be aware of this dynamic and actively guard against it. Quantifying the Invisible Majority The survivorship-bias framework carries immediate quantitative implications. Population estimates derived from the known sample are necessarily lower bounds on the true ISO number density. To estimate the fraction of parameter space currently accessible to detection, we consider four independent axes of observational sensitivity. (i) Size: current surveys require effective diameters of at least 100 m at distances of 1 AU in their sensitivity to reflected sunlight. Power-law extrapolation of Solar System size distributions suggests that objects below this threshold outnumber those above it by orders of magnitude15, so optical surveys sample a small fraction of the actual size distribution. Indeed, Peña-Asensio and Seligman34 argued that a power-law extrapolation from spacecraft-detected interstellar dust to kilometer-scale ISOs overpredicts the number of intermediate-sized interstellar meteoroids by 2–7 orders of magnitude relative to meteor survey constraints, revealing a flux-gap across the very size range where current instruments are blind. (ii) Albedo: optical surveys are sensitive to reflected sunlight and therefore preferentially detect objects with moderate-to-high albedo. Bodies with geometric albedo below ~0.02 — analogous to the darkest known asteroids, would fall below detection thresholds at distances beyond ~0.5 AU; we estimate roughly 30% of the albedo distribution is currently accessible. (iii) Velocity: the requirement for multi-night arc detections to confirm an object and compute an orbit imposes an effective velocity ceiling of approximately 200 km/s; faster objects produce a faint, long streak or single-frame detections that current pipelines discard. Based on theoretical velocity distributions for stars in the solar neighborhood, approximately 40% of ISOs are expected below this threshold. (iv) Activity: Two of the three detected ISOs (2I/Borisov and 3I/ATLAS) exhibited outgassing and dust production that amplified their apparent brightness by factors of 10–1000 relative to their bare nuclei; inactive bodies of equivalent nucleus size would be 2.5–7.5 magnitudes fainter8,15. The sole inactive detection, 1I/’Oumuamua, required a closest approach of just 0.25 AU to Earth, an exceptionally rare geometry that underscores how difficult it is to detect ISOs without coma enhancement. We estimate that roughly 10% of ISOs display sufficient activity to produce coma enhancement at heliocentric distances where current surveys operate. Treating these axes as approximately independent, the combined detection fraction is ~0.10 × 0.30 × 0.40 × 0.10 ≈ 0.001, equivalent to about 0.1% of the total ISO parameter space. This estimate is necessarily approximate as the axes are not perfectly independent, and each factor carries uncertainty of at least a factor of two, but it establishes that current surveys are sensitive to a very small fraction of the interstellar population. We emphasize that this is a conceptual estimate intended to illustrate the scale of the problem, not a rigorous statistical bound. Combined with the arrival rate of approximately one 3I/ATLAS-like object per year within 4.5 AU, this implies that multiple interstellar visitors have been transiting the inner Solar System undetected throughout the era of modern sky surveys. Such a revised estimate accounts only for objects that resemble the three survivors. The population of dark, inactive, or fast ISOs remains entirely unconstrained. 2I/Borisov and 3I/ATLAS both exhibited outgassing driven by water and carbon-bearing volatiles, while 1I/’Oumuamua appeared entirely inactive — itself a datum that current models struggle to explain. This is not a property of the interstellar population; it is a property of the detection threshold. Just as Malmquist bias28 distorts flux-limited stellar samples, ISO detection inherits compounding selection effects across all four axes simultaneously, and no forward-model detection function yet exists to correct for them. We are studying the distribution of damage on returning bombers and concluding that engines are rarely hit. Armoring the Engines: A Multi-Modal Detection Architecture Wald’s recommendation was to armor where damage was absent, not where it was present. The analogous prescription for ISO science is to invest in detection capabilities for the classes of objects we are currently not finding. No single instrument can overcome a multi-dimensional survivorship bias. What is required is a complementary architecture in which each modality addresses a specific axis of invisibility. The Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST), with its 8.4-meter aperture and four-night cadence, will push the optical detection threshold to smaller diameters and increase the ISO detection rate from ~1 per decade to potentially several per year29,30. However, Rubin observes only the southern sky. Full temporal coverage requires a northern-hemisphere counterpart such as the planned Argus Array (https://argus.unc.edu/); the proposed Comprehensive ISO Network (CISON) architecture31 would close the geometric gap by combining dual-hemisphere wide-field discovery with rapid high-resolution characterization and selective escalation to interceptor missions. Current pipelines demand multi-night detections to confirm an object and compute an orbit. For ISOs transiting the inner Solar System above ~200 km/s, this window collapses. Real-time machine-learning pipelines operating on single exposures are necessary to capture the fastest visitors. By coupling discovery architecture to predictive classification frameworks, ISO assessment can shift from reactive to anticipatory, identifying objects likely to escape detection before they do. The most fundamental long-term solution lies in gravitational detection. Thoss and Loeb32 showed that proposed space-based gravitational-wave experiments, particularly DECIGO, could detect the perturbation of detector test masses by dark objects streaming through the Solar System, with detection volumes reaching several million kilometers for sufficiently massive perturbers. Although their analysis targets dark matter clumps and primordial black holes, the method applies generically to any unbound massive body and is entirely independent of electromagnetic radiation, albedo, or outgassing. For ISO-scale masses, current projections require extremely close approaches (sub-AU for LISA). This capability therefore remains contingent on future detector sensitivities and is included here to illustrate the complete detection architecture rather than as a near-term solution. Finally, ESA’s Comet Interceptor33 and proposed rapid-response platforms ensure that characterization is not biased toward properties measurable only by remote photometry. In-situ measurements can determine whether an intercepted object is representative or anomalous in ways that remote observation cannot. Discussion and Conclusions We have argued that interstellar object science is subject to a form of survivorship bias that is multi-dimensional, severe, and structurally analogous to the problem Abraham Wald identified in 1943. This conclusion is supported by independent flux analyses34 which demonstrated that spacecraft dust measurements and kilometer-scale ISO detections cannot be connected by a single size-frequency distribution, implying that the detected populations may represent distinct source reservoirs rather than endpoints of a continuous spectrum. In both cases, the sample available for study has been filtered by a process that preferentially removes the most informative cases, and in both cases, the correct response is to direct resources toward the unobserved region of parameter space. The contribution of this Perspective is twofold. First, we propose survivorship bias, as distinct from selection bias, as the appropriate conceptual framework for understanding ISO detection incompleteness, and we distinguish this from the more familiar (and less severe) selection biases that are routinely corrected in other astronomical contexts. Second, we identify the cognitive dimension of the problem: the representativeness heuristic, anchoring, and premature closure operate on small, diverse samples in ways that are well-documented but have not previously been discussed in the ISO literature. Indeed, HST observations have confirmed that 3I/ATLAS itself would have escaped detection without the brightness enhancement provided by its dust coma8, demonstrating that even the detected sample includes objects that nearly failed to ‘survive’ into our catalogs. We emphasize that this perspective is entirely agnostic to the composition and origin of undetected ISOs. The survivorship-bias argument applies equally to icy comets, rocky asteroids, metallic fragments, and any other hypothetical objects. What it requires is a recognition that three objects, however scientifically valuable, cannot be treated as representative without explicit correction for the detection function, and that the path to correction runs not through better statistics applied to three data points, but through the construction of instruments capable of finding the next three hundred. The history of astronomy is, in many ways, a history of overcoming survivorship bias. Every advance in instrumentation, from the optical telescope to the radio dish to the X-ray satellite to a gravitational wave interferometer, revealed populations that were invisible to previous technology. Each time, the newly visible objects were not merely more of the same; they were qualitatively different, populating regions of parameter space that had been structurally inaccessible. There is every reason to expect that the same will hold for interstellar objects. 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Astronomy & Astrophysics, 704, L1. https://doi.org/10.1051/0004-6361/202557337 ABOUT THE POSTING CO-AUTHOR (Image Credit: Chris Michel, National Academy of Sciences, 2023)Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. The paperback edition of his new book, titled “Interstellar”, was published in August 2024. Professional website: https://lweb.cfa.harvard.edu/~loeb/ Social media: https://avi-loeb.medium.com/ https://www.youtube.com/@ProfessorAviLoeb https://open.spotify.com/show/1zhndXkvSY2b8FdjspFpCd https://x.com/ProfAviLoeb View the full article

Galileo Project sensors on top of Sphere in Las Vegas are monitoring the sky in infrared and visible light, in search of anomalous objects. Outliers are identified by artificial intelligence algorithms. (Image credit: Alex Delacroix/Galileo Project)During a Valentine’s Day interview on Saturday, February 14, 2026 with the journalist Brian Tyler Cohen, posted here (and transcribed here), Former President Barack Obama was asked: “Are aliens real?” He responded: “They’re real, but I haven’t seen them. They are not being kept in Area 51.” Cohen then asked: “What was the first question you wanted answered when you became president?” to which Obama replied: “Where are the aliens?” This is not the first time that Obama has commented on this topic. In a 2021 interview, he told the comedian James Corden: “Look, the truth is that when I came into office, I asked … I was like, ‘All right, is there a lab somewhere where we’re keeping the alien specimens and spaceships?’… They did a little bit of research … and the answer was, ‘No’… But what is true — and I’m actually being serious here — is that there’s footage and records of objects in the skies that we don’t know exactly what they are …We can’t explain how they moved, their trajectory … they did not have an easily explainable pattern … So, I think that people still take it seriously trying to investigate and figure out what that is.” These sentiments were echoed in a hearing on September 9, 2025 before the House Oversight and Government Reform Task Force in the Declassification of Federal Secrets, where military personnel described mysterious Unidentified Anomalous Phenomena (UAPs). The visionary Congresswoman Anna Paulina Luna who chairs the UAP task force, accused the Pentagon and intelligence community of a “lack of transparency,” arguing the task force “has been denied access to video and files related to UAP incidents.” Representative Luna added that “The American people are not fragile and do not need to be shielded like children from reality.” “For too long, the issue of Unidentified Anomalous Phenomena — commonly known as UAPs — has been shrouded in secrecy, stigma and in some cases outright dismissal,” Representative Luna said at the start of the hearing. Indeed, governments and intelligence agencies are likely to notice unusual activity near Earth because their state-of-the-art sensors monitor the sky and oceans routinely for national security purposes. But UAPs are under no obligation to be detectable only by government-owned sensors. And so, it makes sense to collect scientific quality data on them and figure out their nature. There is bipartisan consensus on this issue, as evident in congressional hearings on UAPs. This is the stated goal of the Galileo Project under my leadership, as described here. Our research team, which was reenergized by five new young scientists in spring 2026, is operating three scientific observatories in Nevada, Pennsylvania and Massachusetts, in an attempt to measure the distance, velocity and acceleration of rare outliers among millions of objects in the sky. Our facilities include multiple units with infrared and optical cameras that monitor the entire sky at all times at these three locations. The data is analyzed by artificial intelligence algorithms which aim to find objects that behave outside the flight characteristics of human-made technologies. A key element in this identification procedure, which is not available for most UAP data reported so far, involves measuring distances reliably through the method of triangulation. Fast angular motion on the sky could be associated with mundane objects at a close distance. Based on known physics, fast moving objects — including a hypothetical warp drive — are expected to shock the air around them and produce a bright glow as observed for meteor fireballs. Whether Earth is visited by aliens is not a question for insiders who are privy of classified information that is withheld within the U.S. Government, but a scientific question that can be best answered openly within the mainstream of science. Aside from UAPs near Earth, a new path for related scientific discoveries is offered within the new astronomical frontier of interstellar objects which pass near Earth — like 3I/ATLAS, or interstellar meteors which collide with Earth — as reported here in a new paper that I co-authored last week with Richard Cloete, the `Oumuamua-Laukien postdoctoral fellow within the Galileo Project. Perhaps one day, the state of the Union address by the U.S. President will include an official statement on the “State of the Universe.” We should welcome visitors from interstellar space who can inform us on what lies far and beyond our terrestrial experiences. After all, the cosmos includes much more real estate and resources than we possess here on Earth. If we find no scientific evidence for aliens, so be it. But it is definitely worth trying to search for them before dismissing the notion of interstellar dating partners. Staying alone is often a self-fulfilling prophecy voiced by people who refuse to admit that the search for a partner is worthwhile. This Valentine’s Day, we must remember that “Are we alone?” is the most romantic question in science. ABOUT THE AUTHOR (Image Credit: Chris Michel, National Academy of Sciences, 2023)Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. The paperback edition of his new book, titled “Interstellar”, was published in August 2024. View the full article