Greenish Glow of Interstellar Comet 3I/ATLAS | Gemini North Telescope

Greenish Glow of Interstellar Comet 3I/ATLAS | Gemini North Telescope

Gemini North captured this new image of Comet 3I/ATLAS after it reemerged from behind the Sun on its path out of the Solar System. On November 26, 2025, scientists used the Gemini Multi-Object Spectrograph (GMOS) on Gemini North at Maunakea in Hawai‘i to obtain this image of the third-ever detected interstellar object, Comet 3I/ATLAS. The new observation reveals how the comet has changed after making its closest approach to the Sun. Gemini North is one half of the International Gemini Observatory, partly funded by the U.S. National Science Foundation (NSF) and operated by NSF NOIRLab.

After emerging from behind the Sun, 3I/ATLAS reappeared in the sky close to Zaniah, a triple-star system located in the constellation Virgo. This image is composed of exposures taken through four filters—blue, green, orange, and red. As exposures are taken, the comet remains fixed in the center of the telescope’s field of view. However, the positions of the background stars change relative to the comet, causing them to appear as colorful streaks in the final image.

What remains unknown is how the comet will behave as it leaves the Sun's vicinity and cools down. Many comets have a delayed reaction in experiencing the Sun's heat due to the lag in time that it takes for heat to make its way through the interior of the comet. A delay can activate the evaporation of new chemicals or trigger a comet outburst. Gemini will continue to monitor the comet as it leaves the Solar System and detect changes in its gas composition and outburst behavior.

Learn more about the Gemini North Telescope:
https://noirlab.edu/public/programs/gemini-observatory/gemini-north/

Image 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)
Image Date: Nov. 26, 2025
Release Date: Dec. 12, 2025

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