New image of comet 3I/ATLAS shows strange green glow, the effects of its close approach to the Sun
A brand new image has been released showing comet 3I/ATLAS, as observed by the Gemini North telescope.
Comet 3I/ATLAS made headlines in 2025 when it was discovered passing through our Solar System, having formed around a distant star.
It’s probably the oldest comet we’ve ever seen, and one of only three interstellar objects ever discovered.
The new image shows the effects of comet 3I/ATLAS’s close approach to our Sun towards the end of 2025.
Credit: NASA/JWST
The Gemini North telescope is located on top of Maunakea, a dormant volcano in Hawaii.
This image of 3I/ATLAS follows a previous image of the comet captured by Gemini North, which was released in July 2025.
It was captured after the comet reemerged from behind the Sun during its journey through our Solar System.
Comet 3I/ATLAS isn’t orbiting our Sun like other comets: instead, it entered our Solar System from interstellar space, and will eventually exist our Solar System, then will be gone from our view forever.
Image of comet 3I/ATLAS captured by the Gemini North telescope, 26 November 2025. Credit: International Gemini Observatory/NOIRLab/NSF/AURA/B. Bolin. Image Processing: J. Miller & M. Rodriguez (International Gemini Observatory/NSF NOIRLab), T.A. Rector (University of Alaska Anchorage/NSF NOIRLab), M. Zamani (NSF NOIRLab)
About the image
These Gemini North images of comet 3I/ATLAS were captured on 26 November 2025 by astronomers using the telescope’s Gemini Multi-Object Spectrograph instrument.
The observations show how much the comet has changed since its close approach to the Sun.
Comets like 3I/ATLAS contain lots of frozen ice, and so a close approach to a star like our Sun causes it to heat up, venting gases into space.
The images were captured as part of a public outreach initiative by NSF NOIRLab, the U.S. National Science Foundation centre for ground-based optical-infrared astronomy.
Gemini North’s new image of 3I/ATLAS was captured using four filters of blue, green, orange and red.
Comets move quickly across the sky, relative to background stars, and so the telescope had to track its movement, keeping it in frame in order to capture long photographic exposures.
This causes the background stars to appear as streaks in the image.
However, the final image, seen below, has been processed to keep the stars in place.
Image of comet 3I/ATLAS captured by the Gemini North telescope, 26 November 2025. This final image has been processed to correct streaking background stars. Credit: International Gemini Observatory/NOIRLab/NSF/AURA/B. Bolin. Image Processing: J. Miller & M. Rodriguez (International Gemini Observatory/NSF NOIRLab), T.A. Rector (University of Alaska Anchorage/NSF NOIRLab), M. Zamani (NSF NOIRLab)
Green glow
Earlier images of comet 3I/ATLAS captured by the Gemini South telescope, which is located in the Chilean Andes, show the comet with a red hue.
But in these Gemini North images, the comet appears to have taken on a green colour.
Scientists say this is caused by light emitted by gases in the comet’s coma, which are evaporating as the comet heats up.
Gases include diatomic carbon, scientists say, which emits light at green wavelengths.
Comet 3I/ATLAS captured by the Gemini Multi-Object Spectrograph (GMOS) on Gemini South at Cerro Pachón in Chile, 27 August 2025. Image composed of exposures taken through red, green, blue and ultraviolet filters. Credit: International Gemini Observatory/NOIRLab/NSF/AURA/Shadow the Scientist. Image Processing: J. Miller & M. Rodriguez (International Gemini Observatory/NSF NOIRLab), T.A. Rector (University of Alaska Anchorage/NSF NOIRLab), M. Zamani (NSF NOIRLab)
A long journey ahead
Scientists say the Gemini telescopes will continue to monitor comet 3I/ATLAS as it makes its way out of our Solar System.
As it does so, the comet should begin to cool down again but, scientists say, some comets do experience delayed reactions to warming by the Sun, as that solar heat makes its way down into the comet’s interior.
This might result in a delayed outburst of gases on the comet’s surface.
“Sharing an observing experience in some of the best conditions available gives the public a truly front-row view of our interstellar visitor,” says Bryce Bolin, a research scientist from Eureka Scientific, who led the science program.
“Allowing the public to see what we do as astronomers and how we do it also helps demystify the scientific and data collection process, adding transparency to our study of this fascinating object.”
