Interstellar Comet 3I/ATLAS Reveals a Green Glow After Closest approach to the Sun
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A newly released image of interstellar comet 3I/ATLAS showcases a striking greenish hue, offering astronomers valuable insights into the comet’s composition and behavior as it journeys away from the Sun. Observations captured on November 26, 2025, using the Gemini Multi-Object Spectrograph (GMOS) on the Gemini North telescope in Hawai’i, reveal changes in the comet following its closest approach to our star on October 30, 2025.
A Visitor From Beyond Our solar System
3I/ATLAS is a unique celestial object, originating from outside our solar system. After emerging from behind the Sun, the comet became visible near zaniah, a triple-star system within the constellation Virgo. The recent observations provide a rare opportunity to study an interstellar visitor up close, shedding light on the building blocks of planetary systems beyond our own.
Unveiling the Comet’s Composition Thru color
The images, obtained through a public outreach initiative organized by NSF NOIRLab in collaboration with Shadow the Scientists, reveal a significant shift in the comet’s appearance. While earlier observations,taken at Gemini South in Chile,showed a reddish tint,the latest data displays a faint greenish glow.
According to astronomers, this color change is due to the evaporation of gases within the comet’s coma – the cloud of gas and dust surrounding its icy nucleus. Specifically, the glow is attributed to light emitted by diatomic carbon, a highly reactive molecule composed of two carbon atoms that emits light at green wavelengths as it heats up.
“Sharing an observing experience in some of the best conditions available gives the public a truly front-row view of our interstellar visitor,” a researcher with Eureka Scientific stated. “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 openness to our study of this fascinating object.”
How the Images Were Captured
The new images are a composite of exposures taken using four filters: blue, green, orange, and red. As the telescope observed 3I/ATLAS,the comet remained stationary in the field of view,while the background stars appeared as colorful streaks due to their relative motion. This technique allowed for a detailed analysis of the comet’s coma and the gases it releases.
What Lies Ahead for 3I/ATLAS?
Despite these recent discoveries, many questions remain about the comet’s future behavior. Astronomers acknowledge that comets often exhibit a delayed reaction to solar heating, as it takes time for the heat to penetrate the comet’s interior.
“What remains unknown is how the comet will behave as it leaves the sun’s vicinity and cools down,” astronomers noted. This delay could trigger the evaporation of new
Why: Astronomers are studying interstellar comet 3I/ATLAS to understand the composition and origins of planetary systems beyond our own.
Who: The observations were made by astronomers using the Gemini Multi-Object Spectrograph (GMOS) on the Gemini North telescope in Hawai’i, with public outreach support
