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By USH
Everything we know about 3I/ATLAS to date:
On July 1, 2025, the Asteroid Terrestrial-impact Last Alert System (ATLAS) station at Río Hurtado, Chile, detected something extraordinary: a fast-moving object flagged with the provisional designation A11pl3Z, later named 3I/ATLAS, also cataloged as C/2025 N1 (ATLAS).
At first glance, it was classified as a comet. But almost immediately, astronomers realized that this visitor was anything but ordinary.
3I/ATLAS imaged by the James Webb Space Telescope's NIRSpec on 6 August 2025.
Why 3I/ATLAS is different.
1. Interstellar Origins Like ʻOumuamua (1I/2017 U1) and Borisov (2I/2019 Q4) before it, 3I/ATLAS is only the third confirmed interstellar object to enter our solar system. Its steep hyperbolic orbit—with an eccentricity greater than 1.02—proves it is not gravitationally bound to the Sun.
2. A Composition Unlike Any Comet Most comets are rich in water ice. Not 3I/ATLAS. Spectroscopic analysis from both the Hubble Space Telescope and James Webb Space Telescope (JWST) revealed it is dominated by carbon dioxide with one of the highest CO₂-to-water ratios ever measured. This makes it chemically alien compared to the comets that formed in our own solar system.
3. A Tail That Breaks the Rules Comets typically sprout tails pointing away from the Sun, driven by sublimating ice. 3I/ATLAS, however, displays a dust plume angled toward the Sun—a tail in the “wrong” direction. This phenomenon has never been observed in a natural comet and suggests either unusual physics or engineered behavior.
4. Perfectly Aligned Trajectory Instead of cutting randomly across the solar system, 3I/ATLAS travels almost exactly along the ecliptic plane, the flat orbital path where Earth, Mars, and most of the planets reside. Statistically, the odds of a random interstellar object aligning this precisely are less than 0.005%.
5. Unexplained Acceleration Data from radar tracking and JWST confirm subtle but persistent non-gravitational acceleration. Normally, such changes are explained by outgassing jets. Yet Webb detects no coma, no jets, no thermal signature to explain the push. Instead, the acceleration resembles controlled propulsion, similar to how an ion engine expels dust or gas for thrust.
6. Forward-Facing Glow: Instead of a tail behind it, 3I/ATLAS shines with a glow ahead of its motion, almost as if it were illuminating its path.
7. Stabilized Rotation: Unlike natural tumbling comets, it appears to maintain attitude control, consistent with artificial stabilization.
8. Speculations of nuclear propulsion: Harvard astrophysicist Avi Loeb, already known for his bold ʻOumuamua interpretations, has highlighted its non-gravitational acceleration and trajectory. He even speculated that 3I/ATLAS might be nuclear-powered technology, perhaps venting dust as thrust.
9. 3I/ATLAS will not simply zip past and leave. Its calculated path takes it past several key planets: Venus flyby – August 2025 Mars encounter – September 2025 Jupiter flyby – late 2026
Tilted view of 3I/ATLAS's trajectory through the Solar System, with orbits and positions of planets shown. Such a sequence of planetary passes looks less like coincidence and more like a deliberate survey trajectory.
Finally, on October 30, 2025, the object will reach perihelion, its closest approach to the Sun. Crucially, at that moment it will be hidden directly behind the Sun from Earth’s perspective, a perfect opportunity for a stealth maneuver if it is indeed under intelligent control.
10. And the latest news on this object is that 3I/ATLAS shows signs of alien electroplating. Astronomers using the Very Large Telescope (VLT) in Chile have detected something never before seen in a natural comet, a plume of pure nickel gas, laced with cyanide, but completely lacking iron.
This is not how comets behave. In every known case, nickel and iron are paired together in space rocks, asteroids, and cosmic debris. The absence of iron in 3I/ATLAS makes it impossible to explain through natural processes.
The nickel-cyanide combination looks eerily familiar to something we know from human technology: nickel-cyanide electroplating. This industrial process is used to coat and protect metals like iron, creating a corrosion-resistant shell. When heated, such a coating releases nickel vapor and cyanide gas, the exact chemical fingerprint astronomers now see venting from 3I/ATLAS.
Renowned astrophysicist Avi Loeb has already highlighted this bizarre discovery, stressing that the nickel-only signature matches industrial alloy production rather than anything we’d expect from natural comet chemistry.
Pure nickel without iron: impossible in natural comets. Nickel + cyanide plume: matches electroplated coatings. Artificial signature: hallmark of industrial processes.
Putting it all together, so far: It is an interstellar visitor on a hyperbolic escape path. It has a carbon dioxide–dominated composition, nearly devoid of water. It has a dust plume points toward the Sun, breaking cometary rules. It has a trajectory which is perfectly aligned with the ecliptic plane. It shows mysterious acceleration without visible outgassing. It exhibits a forward glow, possible radio emissions, and signs of stabilization. It will perform planetary flybys. It probably has nuclear propulsion. It has an electroplated shell.
Mainstream astronomers remain cautious, still labeling 3I/ATLAS as a comet, but with mounting evidence, we may be staring at the first tangible proof of alien technology crossing our solar system, a probe from another civilization on a reconnaissance mission, silently mapping habitable worlds before making contact.View the full article
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By NASA
Explore Hubble Science Hubble Space Telescope As NASA Missions Study… Hubble Home Overview About Hubble The History of Hubble Hubble Timeline Why Have a Telescope in Space? Hubble by the Numbers At the Museum FAQs Impact & Benefits Hubble’s Impact & Benefits Science Impacts Cultural Impact Technology Benefits Impact on Human Spaceflight Astro Community Impacts Science Hubble Science Science Themes Science Highlights Science Behind Discoveries Hubble’s Partners in Science Universe Uncovered AI and Hubble Science Explore the Night Sky Observatory Hubble Observatory Hubble Design Mission Operations Missions to Hubble Hubble vs Webb Team Hubble Team Career Aspirations Hubble Astronauts Multimedia Images Videos Sonifications Podcasts e-Books Online Activities 3D Hubble Models Lithographs Fact Sheets Posters Hubble on the NASA App Glossary News Hubble News Social Media Media Resources More 35th Anniversary Online Activities 4 min read
As NASA Missions Study Interstellar Comet, Hubble Makes Size Estimate
Hubble captured this image of the interstellar comet 3I/ATLAS on July 21, 2025, when the comet was 277 million miles from Earth. Hubble shows that the comet has a teardrop-shaped cocoon of dust coming off its solid, icy nucleus. Image: NASA, ESA, David Jewitt (UCLA); Image Processing: Joseph DePasquale (STScI) A team of astronomers has taken the sharpest-ever picture of the unexpected interstellar comet 3I/ATLAS using the crisp vision of NASA’s Hubble Space Telescope. Hubble is one of many missions across NASA’s fleet of space telescopes slated to observe this comet, together providing more information about its size and physical properties. While the comet poses no threat to Earth, NASA’s space telescopes help support the agency’s ongoing mission to find, track, and better understand near-Earth objects.
Hubble’s observations allow astronomers to more accurately estimate the size of the comet’s solid, icy nucleus. The upper limit on the diameter of the nucleus is 3.5 miles (5.6 kilometers), though it could be as small as 1,000 feet (320 meters) across, researchers report. Though the Hubble images put tighter constraints on the size of the nucleus compared to previous ground-based estimates, the solid heart of the comet presently cannot be directly seen, even by Hubble. Observations from other NASA missions including the James Webb Space Telescope, TESS (Transiting Exoplanet Survey Satellite), and the Neil Gehrels Swift Observatory, as well as NASA’s partnership with the W.M. Keck Observatory, will help further refine our knowledge about the comet, including its chemical makeup.
Hubble also captured a dust plume ejected from the Sun-warmed side of the comet, and the hint of a dust tail streaming away from the nucleus. Hubble’s data yields a dust-loss rate consistent with comets that are first detected around 300 million miles from the Sun. This behavior is much like the signature of previously seen Sun-bound comets originating within our solar system.
The big difference is that this interstellar visitor originated in some other solar system elsewhere in our Milky Way galaxy.
3I/ATLAS is traveling through our solar system at a staggering 130,000 miles (209,000 kilometers) per hour, the highest velocity ever recorded for a solar system visitor. This breathtaking sprint is evidence that the comet has been drifting through interstellar space for many billions of years. The gravitational slingshot effect from innumerable stars and nebulae the comet passed added momentum, ratcheting up its speed. The longer 3I/ATLAS was out in space, the higher its speed grew.
“No one knows where the comet came from. It’s like glimpsing a rifle bullet for a thousandth of a second. You can’t project that back with any accuracy to figure out where it started on its path,” said David Jewitt of the University of California, Los Angeles, science team leader for the Hubble observations.
The paper will be published in The Astrophysical Journal Letters. It is already available on Astro-ph.
New Evidence for Population of Wandering Space Relics
“This latest interstellar tourist is one of a previously undetected population of objects bursting onto the scene that will gradually emerge,” said Jewitt. “This is now possible because we have powerful sky survey capabilities that we didn’t have before. We’ve crossed a threshold.”
This comet was discovered by the NASA-funded Asteroid Terrestrial-impact Last Alert System (ATLAS) on July 1, 2025, at a distance of 420 million miles from the Sun. ATLAS is an asteroid impact early warning system developed by the University of Hawai’i.
In the meantime, other NASA missions will provide new insight into this third interstellar interloper, helping refine our understanding of these objects for the benefit of all. 3I/ATLAS should remain visible to ground-based telescopes through September, after which it will pass too close to the Sun to observe, and is expected to reappear on the other side of the Sun by early December.
The Hubble Space Telescope has been operating for more than three decades and continues to make ground-breaking discoveries that shape our fundamental understanding of the universe. Hubble is a project of international cooperation between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope and mission operations. Lockheed Martin Space, based in Denver, also supports mission operations at Goddard. The Space Telescope Science Institute in Baltimore, which is operated by the Association of Universities for Research in Astronomy, conducts Hubble science operations for NASA.
To learn more about Hubble, visit: https://science.nasa.gov/hubble
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Related Images & Videos
Comet 3I/ATLAS
Hubble captured this image of the interstellar comet 3I/ATLAS on July 21, 2025, when the comet was 277 million miles from Earth. Hubble shows that the comet has a teardrop-shaped cocoon of dust coming off its solid, icy nucleus.
Comet 3I/ATLAS Compass Image
This image of interstellar comet 3I/ATLAS was captured by the Hubble Space Telescope’s Wide Field Camera on July 21, 2025. The scale bar is labeled in arcseconds, which is a measure of angular distance on the sky. One arcsecond is equal an angular measurement of 1/3600 of o…
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Last Updated Aug 07, 2025 Editor Andrea Gianopoulos Location NASA Goddard Space Flight Center Contact Media Claire Andreoli
NASA’s Goddard Space Flight Center
Greenbelt, Maryland
claire.andreoli@nasa.gov
Ray Villard
Space Telescope Science Institute
Baltimore, Maryland
Related Terms
Hubble Space Telescope Astrophysics Astrophysics Division Comets Goddard Space Flight Center Small Bodies of the Solar System The Solar System
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Science Paper: Hubble Space Telescope Observations of the Interstellar Interloper 3I/ATLAS, PDF (1.57 MB)
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By European Space Agency
Image: A team of astronomers has taken the sharpest-ever picture of the unexpected interstellar comet 3I/ATLAS, using the crisp vision of the NASA/ESA Hubble Space Telescope.
ESA's Planetary Defence Office responded promptly to the discovery of the comet, and has been tracking it since the beginning of July.
Now, Hubble's observations from space are allowing astronomers to more accurately estimate the size of the comet’s solid icy nucleus. The upper limit on the diameter of the nucleus is 5.6 km, but it could be as small as 320 m across, researchers report.
Though the Hubble images put tighter constraints on the nucleus size compared to previous ground-based estimates, the solid heart of the comet presently cannot be directly seen, even by Hubble. Further observations, including by the NASA/ESA/CSA James Webb Space Telescope, will help refine our knowledge about the comet, including its chemical makeup.
Hubble also captured a dust plume ejected from the Sun-warmed side of the comet, and the hint of a dust tail streaming away from the nucleus. Hubble’s data show that the comet is losing dust in a similar manner to that from previously seen Sun-bound comets originating within our Solar System.
The big difference is that this interstellar visitor originated in some other stellar systems, elsewhere in our Milky Way galaxy.
3I/ATLAS is traveling through our Solar System at roughly 210 000 km per hour, the highest speed ever recorded for a Solar System visitor. This breathtaking sprint is evidence that the comet has been drifting through interstellar space for many billions of years. The gravitational slingshot effect from innumerable stars and nebulae the comet passed added momentum, ratcheting up its speed. The longer 3I/ATLAS was out in space, the higher its speed grew.
This comet was discovered by the Asteroid Terrestrial-impact Last Alert System (ATLAS) on 1 July 2025 at a distance of 675 million km from the Sun. 3I/ATLAS should remain visible to ground-based telescopes until September, after which it will pass too close to the Sun to observe. It is expected to reappear on the other side of the Sun by early December.
Icy wanderers such as 3I/ATLAS offer a rare, tangible connection to the broader galaxy. To actually visit one would connect humankind with the Universe on a far greater scale. To this end, ESA is preparing the Comet Interceptor mission. The spacecraft will be launched in 2029 into a parking orbit, lying in wait for a suitable target – a pristine comet from the distant Oort Cloud that surrounds our Solar System, or, unlikely but highly appealing, an interstellar object.
While it is improbable that we will discover an interstellar object that is reachable for Comet Interceptor, as a first demonstration of a rapid response mission that waits in space for its target, it will be a pathfinder for possible future missions to intercept these mysterious visitors.
The research paper based on Hubble observations will be published in The Astrophysical Journal Letters.
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By European Space Agency
Astronomers have confirmed the discovery of a rare celestial visitor: a comet from beyond our Solar System.
Officially named 3I/ATLAS, this newly identified interstellar object is only the third of its kind ever observed, following the famous 1I/ʻOumuamua in 2017 and 2I/Borisov in 2019.
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