3I Atlas
3IAtlas is a rare interstellar comet, detected on July 1, 2025.[1]
It was discovered by the Asteroid Terrestrial-impact Last Alert System -- hence the "atlas" part of its name.[1] The "3i" prefix was prepended because it is Atlas's third interstellar comet.
Astronomers can distinguish interstellar comets from local comets by their velocity.[1] All comets from the Solar System's Oort Cloud or Kuiper Belt will be traveling at less than the Solar System's escape velocity. Interstellar comets' velocities will always be greater than the Solar System's escape velocity.
31 Atlas is both significantly faster than, and considerably larger and more massive, than Ounamoonu and comet Borisov, the two other knonw interstellar comets.[1]
The comet passed near Planet Jupiter on March 16, 2026, on the outward leg of its passage through the Solar System.[2]
On March 20, 2026, NASA opened a database of observations of the comet.[3]
According to New Scientist, scientists who studied the spectra from light reflected from the comet have made several exciting observations.[4] In particular, the Hydrogen in the water and methane from the comet has a much higher isotopic percentage of Dueterium than found in the Solar System.
References
[edit | edit source]- ↑ 1.0 1.1 1.2 1.3 "3I/ATLAS Facts and FAQS". NASA. 2025-11-13. Retrieved 2026-03-01.
- ↑
Avi Loeb (2026-03-16). "3I/ATLAS is Fading Away, Leaving Us to Ponder Over Its 22 Mysterious Anomalies". Medium. Retrieved 2026-03-22.
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.
- ↑
Lauren Leese (2026-03-20). "How Open NASA Data on Comet 3I/ATLAS Will Power Tomorrow's Discoveries". NASA Science. Retrieved 2026-03-22.
The interstellar comet 3I/ATLAS will soon leave our solar system, never to return, but the observations of the comet will live on in NASA’s public data archives. More than a dozen NASA science missions turned their instruments to observe the comet, which is only the third identified object to be visiting our solar system from interstellar space.
- ↑
Alex Wilkins (2026-03-17). "3I/ATLAS: Interstellar comet has water unlike any in our solar system". New Scientist. Retrieved 2026-03-22.
The interstellar comet 3I/ATLAS contains water and carbon molecules at levels never before seen in our solar system. This suggests that it formed around an alien star radically different from and much older than the sun.