Free Astronomy Magazine March-April 2026

19 ASTRO PUBLISHING MARCH-APRIL 2026 C omet 3I/ATLAS streaks across stars and galaxies in this im- age captured by the Gemini Multi- Object Spectrograph (GMOS) on Gemini North on Maunakea in Hawai’i, one half of the Interna- tional Gemini Observatory, partly funded by the U.S. National Sci- ence Foundation (NSF) and oper- ated by NSF NOIRLab. This image is composed of exposures taken through four filters — blue, green, orange, and red. As expo- sures are taken, the comet re- mains fixed in the center of the telescope’s field of view. How- ever, the positions of the back- ground stars change relative to the comet, causing them to ap- pear as colorful streaks in the final image. [International Gemini Observatory/NOIRLab/NSF/AURA/ B. Bolin. Image Processing: J. Miller & M. Rodriguez (Interna- tional Gemini Observatory/NSF NOIRLab), T.A. Rector (University of Alaska Anchorage/NSF NOIR- Lab), M. Zamani (NSF NOIRLab)] A deep image of inter- stellar Comet 3I/ATLAS captured by the Gemini Multi-Object Spectrograph (GMOS) on Gemini North on Mau- nakea in Hawai’i, one half of the International Gemini Observatory, partly funded by the U.S. National Science Founda- tion (NSF) and operated by NSF NOIRLab. The image shows the comet’s coma — a cloud of gas and dust that forms around the comet’s icy nucleus in the vicinity of the Sun. 3I/ATLAS is only the third confirmed interstellar visitor to our Solar System. The exposures tracked the comet as it traveled across the sky, and the final image is composed to freeze the stars in place during the observation. [International Gemini Obser- vatory/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)] 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 de- tect changes in its gas composition and outburst behavior. This collabo- ration with Shadow the Scientists builds on NOIRLab’s tradition of combining cutting-edge science with public engagement, ensuring that remarkable cosmic events are shared as widely as possible. By involving learners directly in ob- serving sessions and data collection, programs like this one not only ad- vance knowledge but also inspire the next generation of explorers. “Sharing an observing experience in some of the best conditions avail- able gives the public a truly front- row view of our interstellar visitor,” says Bolin. “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.” posed 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. How- ever, the positions of the background stars change relative to the comet, causing them to appear as colorful streaks in the final image. In earlier images of the comet, captured dur- ing a Shadow the Scientists session hosted at Gemini South in Chile, it appears to have a red hue. However, in the new image it appears to have a faint greenish glow. This is due to light emitted by gases in the comet’s coma that are evaporating as the comet heats up, including diatomic carbon (C 2 ), a highly reactive mole- cule of two carbon atoms that emits light at green wavelengths. 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 !