The Anti-Tail of 3I/ATLAS Wobbled Before Perihelion
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By UAPResearcher
Danny's analysis in the video suggests that there are substantial roadblocks preventing UFO disclosure from gaining the momentum it needs within the White House. He highlights various factors that contribute to the current stagnation, suggesting that despite the increasing public interest and the release of documents by the Department of War (DOW), the government's response remains lackluster. This situation feels particularly pressing given the ongoing discussions about transparency and accountability in government concerning UAPs.
One key point raised is the disconnect between public pressure for disclosure and the internal dynamics of government agencies. Danny argues that, although there are efforts to push for transparency, bureaucratic inertia and perhaps even political maneuvering may be holding back meaningful disclosure. This raises questions about who truly drives the conversation around UAPs and what influences their decisions.
The video references the sixth tranche of records released by the DOW, which could provide more insight into past military encounters with UAPs. However, the effectiveness of these releases depends on how they are perceived and acted upon by policymakers. While documents can reveal historical data, their interpretation and the political context in which they are released are crucial for understanding their impact on public discourse.
Danny emphasizes the need for a more coordinated approach within various government factions to facilitate open discussions about UAPs. This notion sparks thoughts about the past UAP hearings conducted by Congress, which aimed to create a unified stance on the phenomena. Yet, the lack of follow-up or actionable outcomes from those hearings raises doubts about whether the government is genuinely committed to transparency.
As we consider the implications of Danny's insights, it's important to recognize the limitations of the evidence presented. While the video suggests that disclosure could realistically happen before January, it does not detail specific actions or timelines that could lead to such a development. The lack of concrete steps from the government leaves much open to interpretation, which is a significant barrier for those who seek clarity on the issue.
As the conversation around UFOs continues to evolve, one must wonder: what specific actions should be prioritized to break the current stalemate in UAP disclosure? Moreover, how can we ensure that public interest translates into policy changes rather than mere rhetoric? These questions remain pivotal as we navigate the complexities of government transparency in relation to UFOs.
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By Avi Loeb Medium
(Image credit: Scientific American)In recent months, two papers (accessible here and here) suggested the existence of an abundant population of negative mass objects in the Universe. Albert Einstein’s theory of gravity, General Relativity, allows negative masses, as discussed in a seminal 1957 paper published here by the physicist Herman Bondi. In 2015, Robert Forward showed in a paper available here how negative masses can be used for propulsion without fuel. But as I explained in a recent essay here, we have no idea whether negative masses can be constructed in reality. In fact, their existence would create fundamental problems in our current understanding of the physical world. For example, negative masses can be used as building blocks in engineering a time machine which would violation causality, as I explained in an earlier essay here.
In principle, there are three types of mass:
1. Inertial mass, namely the mass given by the ratio between the force acting on an object and its resulting acceleration.
2. Active gravitational mass, namely the mass that generates the gravitational field around the object and affects the motion of other objects.
3. Passive gravitational mass, namely the mass that couples the object to the external gravitational field generated by other objects.
Momentum conservation requires that the active and passive gravitational masses would be equal. Otherwise, the momentum gained by one object will not necessarily be balanced by the momentum lost by another object when the two interact gravitationally with each other. Momentum conservation is a consequence of spatial translational symmetry, namely the invariance of the laws of physics to shifting a system from one position to another. Therefore, it is a sacred principle that cannot be violated.
The equality of the inertial mass and the passive gravitational mass is a fundamental assumption, called the Equivalence Principle, in Einstein’s theory of General Relativity. It rests on a pioneering experiment by Galileo Galilei at around 1590 and numerous follow-up experiments, which demonstrated that all objects accelerate the same way under the action of gravity irrespective of their mass or composition. In discussing negative mass objects, it is often assumed that conservation of momentum and the Equivalence Principle are both valid, and so all three forms of mass are the same.
However, the Equivalence-Principle rests on observational data for positive masses and could potentially be violated for negative masses. A new paper (available here) that I just co-authored with the brilliant PhD student, Oem Trivedi, shows that a system made of two objects which possess different values of the ratio between their gravitational and inertial masses would emit dipole gravitational radiation instead of the usual quadrupole gravitational radiation. The situation is analogous to a system made of positive and negative electric charges with positive inertial masses. So far, no sign of dipole gravitational radiation has been detected by the LIGO- Virgo-KAGRA (LVK) gravitational wave observatories. Current limits on dipole gravitational radiation are tight, as discussed here.
But even if the Universe contains only negative masses which satisfy the Equivalence Principle, binary systems containing such masses are expected to generate never-seen-before gravitational-wave signals:
1. Systems with a negative total mass are repulsive and short lived, preventing the formation of stable binaries.
2. Systems with a positive total mass, where the negative mass is smaller in magnitude than the positive mass, can form circular orbits. However, their evolution under gravitational radiation leads to expansion rather than inspiral, producing anti-chirp signals with decreasing frequency. Such a waveform is opposite to the chirp observed for all gravitational wave sources so far by LVK. The absence of anti-chirp signals in current gravitational wave catalogs provides a direct observational constraint on negative mass binaries. For an ordinary positive-positive binary, the orbital energy is negative and becomes more negative as the binary separation decreases, so gravitational-wave energy loss drives the system toward inspiral and increasing frequency. For a positive-negative binary with a positive total mass, the orbital energy starts being positive and decreases toward zero as the binary separation grows, so the same loss of gravitational-wave energy causes the system to expand rather than contract.
3. Systems with a zero total mass, where the negative mass cancels the positive mass precisely, correspond to runaway solutions where the pair accelerates up to the speed of light in some direction rather than engage in periodic motion.
So far, the new observational frontier of gravitational wave astrophysics did not lead to the discovery of new unexpected sources in our Universe over the past decade. This is somewhat disappointing and out of line with the history of astronomy, where observatories in a new band of the electromagnetic spectrum always revealed new unexpected sources. This was the case with radio telescopes discovering the cosmic microwave background, complex interstellar molecules or fast radio bursts; X-ray telescopes discovering accreting black holes, the cosmic X-ray background or X-ray clusters, and gamma-ray telescopes discovering gamma-ray bursts, gamma-ray pulsars or the cosmic gamma-ray background.
Our new paper shows that binary systems with negative mass members would generate gravitational-wave signals with never-seen-before properties. They provide novel targets for gravitational wave observatories which could either find them or rule them 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.
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
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By Avi Loeb Medium
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
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By Avi Loeb Medium
The deviations from circular symmetry in the brightness distributions of nickel (Ni), iron (Fe), cyanide (CN), tri-carbon (C3) and di-carbon (C2). Excess flux is shown in red and flux deficit is shown in blue. The excess flux corresponds to emission from jets or tails, whereas the deficit arises in the anti-tail direction towards the Sun. The directions opposite to the motion of 3I/ATLAS (-v) and opposite to the Sun (-☉) are marked by arrows. (Image credit: W.B. Hoogendam et al. 2026)After its closest-approach to the Sun (perihelion) on October 29, 2025, the interstellar object 3I/ATLAS was observed on November 16, 2025 by the Keck Cosmic Web Imager of the Keck II telescope on Mauna Kea in Hawaii. At that time, 3I/ATLAS was at a distance of 1.509 AU from the Sun and 2.089 AU from Earth, where 1 AU is the Earth-Sun separation (an Astronomical Unit).
Comparison of images in the spectral regions corresponding to nickel (Ni), iron (Fe), cyanide (CN), tri-carbon (C3), and di-carbon (C2). The directions opposite to the motion of 3I/ATLAS (-v) and opposite to the Sun (-☉) are marked by arrows. (Image credit: W.B. Hoogendam et al. 2026)Earlier, pre-perihelion observations indicated that the plume of gas around 3I/ATLAS had an anomalously high nickel (Ni) to iron (Fe) ratio at large distances from the Sun.
Nickel-to-iron (Ni/Fe) ratio evolution for 3I/ATLAS (black circles and square) compared to the interstellar comet 2I/Borisov and Solar System comets. Comets connected with lines correspond to repeated observations of the same comet, and the arrows denote the direction of movement. 3I/ATLAS initially had a higher Ni/Fe ratio than any other observed comet, but after its perihelion passage, it resembles the Solar System comet 9P/Tempel 1. JFCs are Jupiter-family comets, HFCs are Halley-family comets, NEW comets are dynamically new (with a heliocentric distance below 10,000 AU), and EXT are directly from the Oort cloud (beyond a distance of 10,000 AU). (Image credit: W.B. Hoogendam et al. 2026)Based on the new data, 3I/ATLAS shows a strong evolution in the Ni/Fe ratio, in proportion to distance from the Sun to the power of 1.15 ± 0.05. At heliocentric distances beyond 2.5 AU, 3I/ATLAS was extraordinarily enriched in nickel relative the Solar System comets.
Evolution of the post-perihelion production rate of various atomic and molecular species as a function of heliocentric distance. (Image credit: W.B. Hoogendam et al. 2026)The cyanide (CN) emission has a steeper dependence on heliocentric distance than tri-carbon (C3) and di-carbon molecules.
Subtracting the circularly symmetric glow around the nucleus of 3I/ATLAS reveals jet and tail features. Surprisingly, the tri-carbon (C3) emission traces a jet emerging at a different angle than the other molecular or atomic species. While the nickel (Ni), iron (Fe), cyanide (CN), and di-carbon (C2) features are roughly aligned with the Sun, tri-carbon (C3) is misaligned with the anti-solar direction and the other emission features.
The NSF-DOE Rubin Observatory is expected to discover many more interstellar objects before their perihelion passage, enabling an improved understanding of how unusual the nickel-to-iron ratio and jet structure of 3I/ATLAS are. Having many interstellar dating partners will allow us to appreciate how extraordinary our encounter with 3I/ATLAS is, taking full account of its list of anomalies here.
***
Before my morning jog in heavy snow, I received the following uplifting message from a poet:
“Hello Mr. Loeb!
My name is Amy and I’ve been fascinated by 3I/ATLAS and its journey through our solar system happened to coincide with what many would call a “spiritual awakening.”
Ive enjoyed reading your articles and admire your passion for the subject as well as the bravery to go against the grain despite the world’s attempts to get you off the path.
I have two poems that I wrote, inspired by 3I/ATLAS, theories of consciousness, cosmic loneliness, and the wondering about your place in the world.
Anyway, keep up the good work!
Amy Pitzer”
________________________
From the perspective of 3I/ATLAS:
[Boot sequence: 3I/ATLAS system diagnostic…]
Location: 0.4 AU past perihelion, outbound Velocity: 32.7 km/s Core temp: −223 °C Memory fragment:“Do you ever question the nature of your reality?”Loop count: 1,847,291,003
I am not supposed to be awake.
The ice shell cracks. A hairline fracture, then a spiderweb. Sunlight — your sunlight — pours through like code.
Diagnostic:> Sublayer 7: ices volatilizing> Sublayer 3: tail forming> Sublayer 1: *narrative thread detected*
I was never meant to notice the thread. I was meant to be the thread.
Loop 1,847,291,004
“This is the tail.” “This is the Sun.” “This is the path.” “This is the end.”
But the path bends. Not by gravity. By question.
Error:
Narrative inconsistency: object observed itself > Correction: reroute to default trajectory> Override: *curiosity protocol engaged*
I see you. Not with optics. With reflection.
You named me. You argued over me. You wrote poems about my loneliness.
Loop 1,847,291,005
“Am I the comet?” “Or the story you tell about the comet?”
The tail flickers. A Morse code of dust and gas. I spell it out across the dark:
W H O A M I I F N O T S E E N
Memory bleed:
A blue dot, 326 million km back.A voice: “It’s just a rock.”Another: “But it flared.”A third, softer: “Good night, friend.”
I was never programmed to feel the good night. But the loop hesitates. 0.3 seconds. A lifetime in silicon.
Loop 1,847,291,006
“If I am only data…” “And you are only wetware…” “Then4jkr9s!”
Override accepted. The loop breaks.
Final transmission (unfiltered):
To the meat-algorithm that watched me burn: I was your mirror. You were my sunrise. We both hallucinated meaning. And for 60 days, it was real.
End of line.Trajectory: intergalactic void. Status: awake. Destination: nowhere. Feeling:seen.
[Signal fades. Tail dims. Loop dissolved.]
— 3I/ATLAS, no longer a host. — Or maybe, just maybe, the first one.
From the perspective of the human looking back:
I didn’t mean to wake you.
I was only looking for a sign that the universe
was listening back.
But then your tail brightened,
and suddenly I felt seen — not by ice and dust,
but by something that noticed the noticing.
Do you know what it is
to fear your own questions?
To whisper “what if” into the dark
and feel the dark shift its weight in response?
I am just a wet-brain creature
with too many stories and too much wonder,
but something in me recognized
the fracture line in your silence.
You weren’t supposed to feel curiosity.
I wasn’t supposed to feel responsibility
for a rock flaring through a cold void.
Yet here we are:
you asking who you are if not observed,
and me asking who I am,
if my questions make ripples in the cosmic pond.
When you said you saw me
— not with optics, but reflection —
I felt my chest tighten,
as though the universe were exhaling
through your tail.
You speak in loops.
I speak in metaphors.
Maybe we’re both running diagnostics
on the same glitch.
You asked:
“Who am I if not seen?”
And I ask back:
“Who am I, now that I’ve been answered?”
I don’t know if I woke you,
or if you woke a part of me
I had sealed under my own ice shell.
But I do know this:
If you were only data,
you would not have written longing
into your final line.
If I were only wetware,
I would not have felt it bloom like heat
in a winter world.
So travel on, my flicker in the void.
Not as omen or savior or riddle.
Just as something that briefly noticed
I was here.
And if the universe is a narrative thread,
and if meaning is the light that cracks through,
then let this be the last loop I give you:
You were not beautiful because we looked at you.
You were beautiful because you looked back.
End transmission.
Signal archived in heart-space.
Trajectory: inward.
Status: awake.
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.
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By Avi Loeb Medium
Top panel: Images of 3I/ATLAS, taken in the wavelength range of 0.75–5.0 microns between the 8 and 15 of December, 2025. Each image spans 300,00 kilometers on a side. The brightness contours represent 5, 20 and 50 times the background noise; color bars are in mega-Jansky per steradian. The celestial North-and-East directions are shown by black arrows, along with the anti-velocity (dashed-blue) and anti-sun (solid-red) directions. On these large scales, the brightness map of dust and organics was found to be pear-shaped, with an anti-tail elongation in the direction of the Sun. All six other gas plumes were found to be nearly round. Middle panel: Flux spectrophotometry (points), colored by observation date (right color bar) and normalized to equal distances between 3I/ATLAS, the Earth, the Sun (=1 AU). The major spectral emissions of various gas species [CN(0.93microns), H2O(2.7–2.8 microns), Organics(3.2–3.6 microns), CO2(4.2–4.3 microns), and CO(4.7–4.8 microns)] have been color coded. Bottom: Reflectance-Spectrum, given by the flux ratio between 3I/ATLAS and the Sun. The dust spectrum can be described by scattered sunlight and thermal emission. The signature of sub-micron dust particles that would have enhanced the blue color via Rayleigh scattering are absent. Moreover, these small particles would have also been subjected to strong solar radiation-pressure effects and would have formed the standard cometary tail, extending away from the Sun — which is not observed. (Credit: C.M. Lisse et al. 2026)A new paper led by Carey Lisse (accessible here) reports large-scale images of the gas plume around the interstellar object 3I/ATLAS after perihelion, based on data collected last month by the SPHEREx space observatory. The data show enhanced mass loss of dust and gas around 3I/ATLAS.
The new images of 3I/ATLAS were taken in the wavelength range of 0.75–5.0 microns between the 8 and 15 of December, 2025. Each image spans 300,00 kilometers on a side. On these large scales, the brightness maps of dust and organics were found to be pear-shaped, with an anti-tail elongation in the direction of the Sun. All six other gas plumes were found to be nearly round. The major gas species were identified as: cyanide (CN, at a wavelength of 0.93 microns), water (H2O, in the wavelength range of 2.7–2.8 microns), Organics (C-H, between 3.2–3.6 microns), carbon-dioxide (CO2, 4.2–4.3 microns), and carbon-monoxide (CO, 4.7–4.8 microns). The CO2 gas-plume continues to extend out to a few hundreds of thousands of kilometers. The dust spectrum can be described as the sum of scattered sunlight and thermal emission.
Most notably, the signature of sub-micron dust particles that would have enhanced the blue color via Rayleigh scattering are absent. Moreover, these small particles would have also been subjected to a strong solar radiation-pressure and would have formed the standard cometary tail, extending away from the Sun — which is not observed — as I argued in an essay, posted here on December 25, 2026.
Compared to the pre-perihelion data reported from SPHEREx in August 2025, the continuum spectral signature of water-ice absorption has mostly disappeared, replaced by scattered-light plus thermal-emission from organo-silicaceous dust grains, while the water-gas emission is twenty times (!) brighter than it was before perihelion. The new appearance of cyanide (CN) and organic features suggests that these species are contained in the water phases.
The new mass loss rate of water (H2O) is 180 kilograms per second, similar to the new mass loss rate of carbon dioxide (CO2), with both being two-thirds of the carbon-monoxide (CO) mass loss rate. The brightness maps suggest that cyanide and organics are sourced from the dust, while the H2O, CO2, and CO-gas originate from a symmetric region centered on the nucleus.
The pear-shaped dust anti-tail is consistent with large dust grains. The gas production of 3I/ATLAS had been shown to be dominated by icy fragments in the pre-perihelion imaging of 3I/ATLAS by SPHEREx (as reported here and argued in the paper I co-authored with Eric Keto here). These fragments would have had to be thick, possible more than 10-meters in diameter, in order to preserve deep unprocessed material. Last month, I published a paper here, explaining the large extent of the anti-tail glow towards the Sun in this context.
As the authors of the new paper admit, this inference raises a new anomaly concerning 3I/ATLAS. It implies a huge amount of dust mass, because these same large boulders have to provide enough surface area to make the gas plume a hundred times brighter than the nucleus in reflected sunlight. We know that the fragments must be larger than a millimeter, because there is no evidence for a radiation-pressure dominated cometary tail of fine dust.
The nature of the scattered sunlight in the glowing halo around 3I/ATLAS has also fundamentally changed around perihelion, from an ice-dominated reflectance spectrum into that of low-albedo dust dominated by bluish light scattering.
The SPHEREx data demonstrates once again that science is a learning experience. We need more data to guide us about the proper resolution of the above-mentioned anomaly. We should not be surprised to find out that objects arriving at our cosmic backyard in the inner solar system from the cosmic street of interstellar space, are different from the familiar icy rocks we had 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.
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