Astronomers are tracking a rare visitor from beyond our solar system as it makes its closest approach to both the Sun and Earth. Interstellar comet 3I/ATLAS is currently exhibiting a period of heightened activity, including a striking greenish glow, as revealed in new images from the Gemini North telescope. This comet – only the third interstellar object ever detected – offers a unique opportunity to study the building blocks of planetary systems around other stars, and scientists are closely monitoring its behavior as it continues its journey through our cosmic neighborhood.
New images from the Gemini North telescope confirm that the interstellar comet 3I/ATLAS is experiencing a period of intense activity, becoming brighter and exhibiting a mysterious greenish glow as it made its closest approach to the Sun at the end of October.
This surge in activity suggests the potential for further bright outbursts of cometary material as 3I/ATLAS moves toward its closest approach to Earth next week. The ability to study interstellar comets provides a unique window into the formation of planetary systems beyond our own.
The images, captured on November 26 by the Gemini North telescope atop Mauna Kea in Hawaii, showcase the comet at one of its peak activity levels to date. As the comet nears the Sun, its icy components are sublimating – transitioning directly from solid to gas – and releasing substantial amounts of dust and gas into space.
This ejected material forms a bright, nebulous atmosphere, known as the coma, around the comet’s core, and a long, glowing tail trailing behind it. The observation highlights the dynamic processes occurring within these celestial bodies as they interact with solar radiation.
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Greenish Glow
Astronomers utilized the Gemini North telescope with four filters – blue, red, orange, and green – to capture the detailed view. Analysis revealed a faint greenish hue emanating from the gas in the comet’s coma, a feature not present in earlier observations made months prior.
The source of this glow isn’t extraterrestrial, but a well-understood chemical phenomenon in cometary astrophysics. The 3I/ATLAS is releasing diatomic carbon – a molecule composed of two carbon atoms – which emits a characteristic green light when exposed to intense sunlight, according to a statement from NOIRLab (National Science Foundation’s NOIRLab), which operates the Gemini North and South telescopes.
Many comets within our solar system exhibit this greenish coloration when activated by the Sun, including “Comet Mother of Dragons” (12P/Pons-Brooks), observed last year, and the recently discovered Comet C/2025 F2 (SWAN). This phenomenon provides clues about the composition of these icy travelers.
Notably, when 3I/ATLAS was first observed by Gemini South in August – months before its close encounter with the Sun – it appeared distinctly reddish, NOIRLab reported. This color change is crucial evidence: as the comet heats up, it’s releasing new molecules into space, offering unprecedented insights into its mysterious composition and history.
Earth Approach
The comet 3I/ATLAS is approaching its closest point to Earth on December 19, when it will pass at a comfortable distance of 270 million kilometers (170 million miles). Astronomers are prepared for what could be a period of even more dramatic activity.
The biggest question now centers on how the comet will behave as it moves away from the Sun and cools down. “What remains unknown is how the comet will behave as it leaves the Sun’s vicinity and cools,” representatives from NOIRLab stated.
Many comets exhibit a delayed reaction to solar heating due to the time it takes for the heat to penetrate their nuclei. This delay can trigger the evaporation of new chemical compounds or initiate a cometary outburst, significantly increasing its brightness.
Interstellar Visitor
3I/ATLAS holds a special place in astronomy as only the third interstellar object ever discovered, following 1I/’Oumuamua and 2I/Borisov. It was detected in late June, traveling through our solar system at an impressive speed of approximately 210,000 km/h (130,000 mph) in a hyperbolic orbit – shaped like a “U”. This trajectory means it will not revisit our neighborhood.
The comet is considered the largest and likely the oldest interstellar object observed to date. While it displays intriguing characteristics – such as large jets of material directed toward the Sun and signs of irradiation during its billions of years of interstellar travel – the vast majority of astronomers and space agencies agree that it is a typical comet. This definitively refutes viral claims suggesting it could be an artificial alien technology.
Dozens of observatories and spacecraft around the solar system are closely monitoring 3I/ATLAS. In-depth study of its composition, trajectory, and origin could reveal crucial details about the mysterious edge of our galaxy and provide new information about the formation of some of the oldest star systems in the Milky Way.
The observation window remains open, and scientists anticipate further surprises from 3I/ATLAS, offering a unique opportunity to unravel the secrets of visitors from beyond our solar system.
