Astronomy and Stars
Discussions about astronomy and stars. As we look further out what can we find in the universe beyond Earth's atmosphere?
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Images of the interstellar object 3I/ATLAS. Thin purple lines indicate the position angle of the detected anti-tail jet at a projected distance of 6,000 kilometers from the brightness peak (dotted red circle). For each frame, the observation date and the start and end times in UTC are shown above the panels, along with the total number of sidereal-tracking exposures and the cumulative integration time. The projected velocity vector (red arrow) and the anti-solar direction (yellow arrow) are marked, as well as the image scale and orientation. Degraded orange lines denote the projected rotation-axis direction, derived from mean value of the anti-tail positions angles, while…
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The top panel shows an image of 3I/ATLAS, taken on December 15, 2025 at 02:28:12 UTC on a 0.25-meter telescope in Calabria, Italy. The bottom panel includes the brightness map from a Larson-Sekanina rotational gradient filter on a fraction of the entire field of view, spanning 0.86 by 0.39 million kilometers and featuring an anti-tail going out to half a million kilometers from 3I/ATLAS in the sunward direction towards the lower left. (Image credit: Toni Scarmato)As of December 15, 2025, the interstellar object 3I/ATLAS arrived at a distance of about 270 million kilometers from Earth. By December 19, 2025, it will get to a perigee distance of 268.9 million kilometers, onl…
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An image of 3I/ATLAS, taken on December 13, 2025 at 21:30:26 UTC with a 0.26-meter telescope in Rayong, Thailand. The field of view spans 0.72 million kilometers on a side at the distance of 3I/ATLAS from Earth, 271 million kilometers. The bottom three panels show the projected brightness map in false colors and black & white, respectively. The top panel shows a rotational-gradient brightness map with a Larson-Sekanina filter. A prominent anti-tail, uncommon for comets, points in the direction of the Sun towards the lower left. (Image Credit: Teerasak Thaluang)As of today, December 14, 2025, the interstellar object 3I/ATLAS is at a distance of about 270.5 million kilo…
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An image of 3I/ATLAS, taken on November 26, 2025 by the Gemini Multi-Object Spectrograph (GMOS) on Gemini North on Maunakea in Hawaii, an observatory funded by the U.S. National Science Foundation (NSF) and operated by NSF’s NOIRLab. This image is composed of exposures taken through four filters — blue, green, orange, and red. The exposures were centered on 3I/ATLAS while the background stars appear as streaks. The teardrop shape of the green glowing halo around 3I/ATLAS features an anti-tail in the direction of the Sun, towards the lower left. (Image Credit: International Gemini Observatory/NOIRLab/NSF/AURA/B. Bolin)Exactly four weeks after its perihelion, on November 26…
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An image of 3I/ATLAS, taken on October 9, 2025 by NASA’s MAVEN spacecraft, when 3I/ATLAS was 56 million kilometers from Mars. (Image Credit: NASA/Goddard/LASP/CU Boulder)When I started my career in astrophysics at Princeton in 1987, my mentor John Bahcall asked me for a list of the computer codes that I developed during my PhD. I humbly informed John that I only use computers rarely, when I need to solve a complex set of ordinary differential equations that have no analytic solution. He followed up by asking: “How do you plan to have a successful career in science without developing the skills for code writing?” At that time, John was not aware of my most important skill.…
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Image of 3I/ATLAS on November 24, 2025 at 1:58 UTC from a 12-inch telescope in Namibia. North is to the right and the sunward direction is towards the upper left. The field of view is 75 by 100 arcminutes, corresponding to 6.6 by 8.8 million kilometers. The blue glow at the bottom right corner of the image is caused by the triple star system Eta Virginis. (Image Credit: Gerald Rhemann and Michael Jäger)Below is a Q&A list that combines questions from various reporters about the interstellar object 3I/ATLAS, a week before its closest approach to Earth: Q: How can a space probe hypothetically resemble a comet? Break it down for us like a 5th grader. A: A comet is identi…
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An image of 3I/Atlas on December 9, 2025 (left panel) shows a sunward jet (right panel, Larson-Sekanina gradient filter) that was also apparent in the Hubble Space Telescope image from November 30, 2025. (Image Credit: Toni Scarmato)There is no doubt that we can learn something new from the interstellar object 3I/ATLAS, irrespective of whether it is an icy rock or a spacecraft. The only obstacle to learning is comet experts who display the arrogance of expertise. How can anyone claim to be an expert of interstellar objects when the sample size includes only two previously known examples, 1I/`Oumuamua and 2I/Borisov and when 3I/ATLAS displays 13 anomalies relative to these…
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An X-ray image of the interstellar object 3I/ATLAS captured by the soft X-ray imaging telescope Xtend onboard the XRISM Observatory of the Japanese Aerospace Exploration Agency (JAXA), displaying a field of view of 3 million kilometers on a side. The image shows a faint emission structure extending out to 400,000 kilometers from 3I/ATLAS. (Image credit: JAXA)The first X-ray detection of the interstellar object 3I/ATLAS was just reported from the soft X-ray imaging telescope Xtend onboard the X-Ray Imaging and Spectroscopy Mission XRISM of the Japanese Aerospace Exploration Agency (JAXA). Xtend consists of an X-ray telescope that focuses incoming X-rays and an X-ray CCD ca…
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An image from a fake AI-generated video on YouTube. (Image credit: Futurism, as reported here)Our perception of reality should be based on verified facts and not AI-generated scripts. In the same way that junk food is bad for the physical health of our body, junk intellectual food is bad for the mental health of our brain. In an interview today on the Will Cain Country podcast (accessible here), I explained that the belief regarding us living in a simulation — akin to a computer game, makes the believers irresponsible. It is a luxury that can be afforded by wealthy individuals; however, those of us who struggle with balancing our bank accounts cannot afford to ignore real…
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Data on 3I/ATLAS from the Atacama Large Millimeter/Submillimeter Array (ALMA). Panel (A): Flux map of the spectral line of hydrogen cyanide (HCN) on September 12, 2025 with contours for the gas components moving towards (blue-shifted) or away (red-shifted) from the observer, overlaid separately. Panel (B): As in panel (A) for September 15. Panel ©: Production rate of methanol (CH3OH) in 3I/ATLAS as a function of distance from the Sun (r_H) in units of the Earth-Sun separation (au). Panel (D): Ratio of methanol to hydrogen cyanide production in solar system comets. The values for 3I/ATLAS of (CH3OH/HCN)=124 and 79, are indicated with purple and yellow boxes for September 1…
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Processed displays (from Toni Scarmato, Italy) of the November 30, 2025 image of the interstellar object 3I/ATLAS, taken by the Hubble Space Telescope. The left panel shows the original 7x270 second exposure, the middle panel shows the Unsharp Mask filter applied to original image to sharpen its features, and the right panel shows the Larson-Sekanina filter for detecting rotational gradients in an image. The right-hand panel show evidence for two jets with a clear anti-tail which is not common in familiar comets. The sunward direction is pointing towards the upper left corner. The image has 0.04 arcsecond per pixel and was taken by the instruments WFC3, UVIS2–2K2C-SUB Fil…
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A post-perihelion image of the interstellar object 3I/ATLAS taken by the Wide Field Camera 3 onboard the Hubble Space Telescope on November 30, 2025. At that time, 3I/ATLAS was 286 million kilometers from Earth. Background stars appear as streaks of light. The glowing halo (coma) has a teardrop shape with an anti-tail elongated towards the Sun. The sunward direction is pointing towards the lower left, as marked by the yellow arrow. (Image credit: NASA, ESA, STScI, D. Jewitt (UCLA), M.-T. Hui (Shanghai Astronomical Observatory). Image Processing: J. DePasquale (STScI).The interstellar visitor 3I/ATLAS was reobserved by the Hubble Space Telescope from a distance of 286 mill…
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The annotated and raw version of the preliminary image of the interstellar object 3I/ATLAS, taken on November 2, 2025 by the navigation camera onboard the Juice spacecraft. (Image credit: ESA)As it arrived to perihelion at a distance of 202.9 million kilometers from the Sun on October 29, 2025, the interstellar visitor 3I/ATLAS was hidden behind the Sun from observatories located on Earth. Nevertheless, a week later 3I/ATLAS came close to ESA’s Jupiter Icy Moons Explorer (Juice) which used five of its science instruments to observe our interstellar visitor. The instruments collected data on the composition and shape of the plume of gas and dust around 3I/ATLAS. The data w…
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(Image credit: Greg Wyatt)We measure our lifespan in units of years — the time it takes the Earth to circle the Sun. Since the Sun was born, the Earth completed 4.6 billion such circles. For comparison, documented human history covers only what happens during the last millionth of their total count. But the Milky-Way galaxy is a Russian doll of disks within a disk. For the same reason that water spirals before it goes down the drain, the gas cloud that made the Sun was orbiting in a disk as it fed the emerging Sun at the center. After the process was over, the residual debris disk made the Earth and the other planets. Fortuitously, the Sun was sufficiently massive to igni…
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Image of 3I/ATLAS on November 22, 2025 at 3:00–5:00 UTC based on stacking of 106 images of 60-second exposures, taken with a 0.30-meter telescope at Sternwarte Feuerstein (http://sfeu.de) in Germany. The image shows a teardrop shape of a coma with an anti-tail in the sunward direction, pointing towards the lower left corner. (Image credit: Prof. Dr. Christina Birkenhake).Over the month of November 2025, post-perihelion images of the interstellar object 3I/ATLAS showed a tear-drop shape of its coma with an extension by about an arcminute towards the Sun. During the same period, the JPL Horizons tracking of 3I/ATLAS reported here a non-gravitational acceleration. Its magnit…
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Image of 3I/ATLAS on November 29, 2025 at 21:53 UTC, taken with a 0.26-meter telescope in Rayong, Thailand. Two prominent jets are observed, including an anti-tail in the sunward direction, towards the lower left. (Image credit: Teerasak Thaluang).Following its detection on July 1, 2025, the light from the interstellar object 3I/ATLAS showed pulsating variability with a period of 16.16 hours. The periodic variability, reported here, was measured to have an amplitude of tens of percent. The observers related this variability to a nucleus with an axis ratio of about 0.8. However, the association of this variability with the ellipsoidal shape of the nucleus is not warranted.…
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Surveys on the Existence of Extraterrestrial Intelligent Life and Effects of Revealing Expert Consensus(Image credit: Omer Eldadi)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 in a peer-reviewed journal) Abstract Vickers et al. (2025) established that 58.20% of astrobiology experts believe intelligent extraterrestrial life likely exists, providing the first empirical baseline for public comparison. We surveyed 6,114 highly educated and scientifically engaged individuals (77.60% bachelor’s degree+; 67.99% high-…
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An image of 3I/ATLAS taken by the NEOSSat 0.15-meter Maksutov orbiting telescope on November 27, 2025, when 3I/ATLAS was at a distance of 1.956 AU from Earth and 1.711 AU from the Sun. The exposure duration is 330 seconds. The field of view is 30 x 25 arcminutes with orientation north-up/east-left. The sunward direction is to the lower left. (Image credit: D. D. Balam (DAO/NRC), C. E. Spratt (ret), D. W. E. Green (CBAT), P. Langill (RAO/U. of Calgary), Omar Elmi (CSA), Jack Williams (CSA) & Canadian Space Agency).To paraphrase the Declaration of Independence in the context of science: “We hold these truths to be self-evident, that all humans are created equal, that th…
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Image of 3I/ATLAS, taken on November 26, 2026. (Credit: Julien de Winter)The non-gravitational acceleration of the interstellar object 3I/ATLAS is routinely updated by Davide Farnoccia on NASA’s JPL Horizons website here. On October 30, 2025, the value of the radial acceleration component A1 — normalized at a heliocentric distance of the Earth-Sun separation (=1 au), was listed as 1.6x10^{-6} au per day squared. By November 24, the coefficient A1 was reduced by a factor of 4 to a value of 4x10^{-7} au per day squared. At that time, I pointed out here that the minimum perijove distance of 3I/ATLAS during its encounter with Jupiter on March 16, 2026 is forecasted to be 53.4…
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(Image credit: Cosmin4000/Getty Images)In the long tradition of scientific wagers, Skeptic magazine publisher and historian of science Dr. Michael Shermer has issued a $1000 bet 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, 02030. Taking him up on that challenge is Harvard astronomer and Director of the Galileo Project Dr. Avi Loeb. The wager is placed through the Long Now Foundation’s Long Bets program (“an arena for competitive, accountable predictions”), which adds a …
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An image of 3I/ATLAS, taken on November 22, 2025 at 19:25 UTC with a 0.5-meter telescope. At that time, 3I/ATLAS was close in projection to the galaxy NGC4454 in the sky. The sunward direction is towards the lower left corner. (Credit: Mitsunori Tsumura)A number of images of the interstellar object 3I/ATLAS were taken on November 22–24, 2205 by amateur astronomers and astrophotographers. They consistently show a glowing coma with tightly-collimated anti-tail and tail. The best image (available here) was taken by Mitsunori Tsumura on November 22 at 19:25 UTC with a 0.5-meter telescope. Given the current distance of 3I/ATLAS from Earth of 300 million kilometers, its tail ap…
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An image of 3I/ATLAS, taken on November 24 at 8:05 UTC with a 0.432-meter telescope in Chile. (Credit: Elena Walter, Liena Dreams)In anticipation of Thanksgiving, I have received over the past day the following letters of gratitude concerning the interstellar object 3I/ATLAS: Letter 1 “Hi Avi! (I use the familiar voice, because I feel like you are humanity’s best friend at this moment — the one unafraid to ask the most important questions to which we do not yet know the answers…and seemingly fearlessly at that!) Since your very earliest writings about 3I/ATLAS, I’ve been looking forward to the emails from my new friend Avi to point out, with all due scientific and profess…
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A false-color image of 3I/ATLAS, taken on November 22, 2025. The sunward direction is towards the lower left. (Credit: Alfons Diepvens, Belgium)The time is ripe to summarize the anomalies of the interstellar object 3I/ATLAS in ascending order of likelihood. Here is the list, split into three categories, along with the probability, P, associated with each item: I. Major anomalies with no simple explanation: 1. P=0.00004: The forecasted perijove distance of 3I/ATLAS during its encounter with Jupiter on March 16, 2026 is 53.445 (+/- 0.06) million kilometers, identical to Jupiter’s Hills radius, 53.502 million kilometers (see here). This match was enabled by the non-gravitati…
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Trajectory of 3I/ATLAS with positions of the planets on November 22, 2025. (Credit: NASA/JPL)Let us suppose, hypothetically, that the interstellar object 3I/ATLAS is a mothership that was designed to seed Jupiter with technological devices. What would be the largest distance from Jupiter that this interstellar gardener should arrive at? For that purpose, 3I/ATLAS must arrive within Jupiter’s radius of gravitational influence — the so-called Hill radius, inside of which Jupiter’s gravity overcomes the gravitational tide from the Sun. Interior to that radius, Jupiter’s gravity wins over the Sun’s gravity and can keep low-speed orbiters bound without the Sun ripping them awa…
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Image of 3I/ATLAS on November 14, 2025. (Credit: Rolando Ligustri)Below is the transcript of a live Q&A that I had this evening about the interstellar object 3I/ATLAS. The video is available here. Question: Welcome to FOX 32 Chicago. I’m Aleksandra Bush, here with Avi Loeb, one of our favorite guests on the show. We love having you on. We’ve gotten so many viewer questions since you started joining us and talking about 3I/ATLAS. We wanted to do a live stream specifically answering questions from our viewers, so if you are watching right now, feel free to put your question in the comments and we might be able to get Avi to answer it live. We’re going to start off with …
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Newly-Discovered Sideways Lines Are Likely a Satellite Streak or Otherwise a Hint for the Release of Smaller Objects by 3I/ATLASA stacked image of 3I/ATLAS based on 20 exposures of 100 seconds each, taken at 4:15 UTC on November 20, 2025. The displayed field has dimensions of 16.7 arcminutes on a side, equivalent to 1.6 million kilometers at the 3I/ATLAS distance of 326 million kilometers. The direction of the Sun is towards the lower left (opposite to the arrow in the middle panel). The image shows two narrow lines directed sideways from the 3I/ATLAS-Sun axis and creating a X-pattern with the tail and anti-tail along that axis. (Credit: M. Jäger, G. Rhemann, and E. Prosp…
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A 3.2 second exposure of 3I/ATLAS on October 2, 2025 by the HiRISE camera onboard the Mars Reconnaissance Orbiter. The directions of the Sun and 3I/ATLAS’ motion are indicated by arrows. (Credit: NASA/JPL-Caltech/University of Arizona)The newly released HiRISE image of the interstellar object 3I/ATLAS available here, shows an extension of the glowing plume in the direction of motion ahead of 3I/ATLAS. It appears like there is something preceding the object that was previously confused with being in the direction of the Sun but is actually in the direction of motion. In previous images like the Hubble Space Telescope image here, the two directions were similar when 3I/ATLA…
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A 3.2 second exposure of 3I/ATLAS by the HiRISE camera onboard the Mars Reconnaissance Orbiter with a spatial resolution of 30 kilometers per pixel. Due to spacecraft jitter and motion during the observation period, the light from 3I/ATLAS is smeared by several pixels. The directions of the Sun and 3I/ATLAS’ motion are indicated by arrows.(Credit: NASA/JPL-Caltech/University of Arizona)On November 19, 2025, NASA broadcasted a press conference here in which new data on the interstellar object 3I/ATLAS was shared for the first time after the U.S. government shutdown. An hour earlier, I was asked by a reporter what I expect from the press conference and I replied: “I do not …
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The MeerKAT radio telescope in South Africa. (Credit: NRF/SARAO)The MeerKAT radio telescope in South Africa conducted on November 5, 2025 a search for narrowband radio transmission from the interstellar object 3I/ATLAS using the commensal backend BLUSE suitable for a real-time search for radio technological signatures. As reported here, a total of 23,689 signals were detected; however, all were determined to not be spatially consistent with the position of 3I/ATLAS and thus were likely caused by human-made radio frequency interference. From these observations, the observers established a detection limit of 0.17 Watts over the frequency range of 900 to 1670 megahertz, appr…
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An image of 3I/ATLAS, combining 24 exposures of 60 seconds each with a 0.2-meter telescope (Celestron EdgeHD 800) in New Mexico, USA between 11:53–12:23 UTC on November 16, 2025. The image shows multiple jets both towards and away from the Sun. The sunward direction is pointing to the lower left corner. (Credit: Satoru Murata)As I explained in an interview with Peter Doocy on “The Sunday Briefing” of Fox News yesterday (accessible here), the foundation of science is based on the humility to learn, not the arrogance of expertise. When comet experts argued that 3I/ATLAS must be a familiar water-rich comet as soon as it was discovered on July 1, 2025, they behaved like artif…
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A sharp image of 3I/ATLAS, combining 24 exposures of 60 seconds each with a 0.2-meter telescope (Celestron EdgeHD 800) in New Mexico, USA between 11:53–12:23 UTC on November 16, 2025. The image shows multiple jets both towards and away from the Sun. The sunward direction is pointing to the lower left corner. (Credit: Satoru Murata)The astrophotographer Satoru Murata released here a stunning image of the interstellar object 3I/ATLAS combining 24 exposures of 60 seconds each with a 0.2-meter telescope (Celestron EdgeHD 800) in New Mexico, USA, on November 16, 2025. The image shows multiple jets both towards and away from the Sun, including an anti-tail and a much longer tig…
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An image of 3I/ATLAS, taken at 22:06 UTC on November 15, 2025, shows a prominent anti-tail along with two tails. The sunward direction is pointing to the lower left corner. (Credit: Teerasak Thaluang, MPC-051, Rayong, Thailand)As of November 15, 2025, the interstellar object 3I/ATLAS still displays a prominent anti-tail as well as tails, according to a new image released by Teerasak Thaluang from a 0.26-meter telescope in Thailand. The physics behind the anti-tail of 3I/ATLAS is unclear. For a natural comet, it could be associated with the release of giant dust particles with an effective radius of ~100 micrometers (as suggested by David Jewitt and collaborators here and …
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