December 12, 2025 - New images taken with the Gemini North telescope in Hawaii confirm that the interstellar comet 3I/ATLAS has gotten brighter and greener since its close flyby of the sun in October.

1 week ago - 3I/ATLAS is a faint comet that does not get very close to Earth or the Sun and was not expected to get brighter than about apparent magnitude 11.5 as seen from Earth. Even at its peak brightness, the comet was not visible to an observer on Earth using the naked eye or smaller binoculars.

November 7, 2025 - "As far as we know, the comet just 'changed color' once when its gas coma first became visible/bright, and it's still like that now (only brighter)," Zhang said. "However, this was already beginning to happen by early September before it got ...

October 30, 2025 - New images of the interstellar object 3I/ATLAS as it approached perihelion on October 29, 2025, reveal rapid brightening and a color bluer…

December 18, 2025 - Hawaii’s Gemini North telescope has captured new images of interstellar comet 3I/ATLAS with a green glow as it remerges from behind the sun.

December 17, 2025 - Discovered over the summer, it ... coma and unusual jets. Recent telescope images show it has grown brighter and greener since passing near the Sun in late October....

March 18, 2026 - The calculated trajectory improved on previous determinations by a factor of 10, thanks to the triangulation between observations from Earth and those from Mars. The improved positional accuracy should help in allowing future observations to ...

November 7, 2025 - The comet is a lot brighter when viewed with bluer filters than redder filters, though the bluer filters are more of a mix of green and blue, and not actually that sensitive to pure blue.

November 3, 2025 - (NOAA/Lockheed Martin) The comet reached perihelion on October 29, and the team's calculations suggest it may have brightened to around magnitude 9, bright enough to be visible through smaller amateur telescopes.

November 4, 2025 - The optical observations show that 3I/ATLAS is now even brighter than when it went in.

The following chart shows the light curve of comet 3I/ATLAS, i.e., its apparent magnitude as a function of time. The curve is calculated using the latest ephemerides provided by JPL Horizons. The magnitude data is sampled with the interval of 2 days. Because of this sampling, inaccuracies may occur for objects that have large variations of brightness over a few days. For comets, large discrepancies can arise between the calculated brightness and the observations due to their highly dynamic, and not always precisely predictable, behavior.

In late November and early December, X-ray telescopes XRISM and XMM-Newton observed the comet, revealing a diffuse X-ray glow around the comet nucleus. This makes 3I/ATLAS the first interstellar comet to have been observed in X-ray light.

November 4, 2025 - New observations reveal that 3I/ATLAS may be turning blue.

April 27, 2026 - 5. Anti-tail: 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.

December 15, 2025 - "Interstellar comet 3I/ATLAS has a post-perihelion greenish glow in time for the holidays," said Bryce Bolin, a research scientist from Eureka Scientific who led the observations, in a

November 1, 2025 - The comet reached perihelion on October 29, and the team's calculations suggest it may have brightened to around magnitude 9, bright enough to be visible through smaller amateur telescopes.

November 2, 2025 - The interstellar comet 3I/ATLAS showed a sharp increase in brightness and also changed color. The reason for this sudden activity remains a mystery to scientists.