Interstellar comet glows green in telescope images from Hawaii

An interstellar comet that wandered into our solar system is putting on a subtle but striking show as it heads back out. Last month, the Gemini North telescope in Hawaii captured new images of Comet 3I/ATLAS after it emerged from behind the sun, revealing a faint greenish glow that wasn't visible in earlier observations.

The shift in color tells a story about what's happening inside the comet. In previous images taken from Chile, 3I/ATLAS appeared reddish. But as it passed closest to the sun and began heating up, new gases started evaporating from its surface. The green hue comes from diatomic carbon—a reactive molecule made of two carbon atoms—glowing as it rises off the comet's icy body.

A Comet Watched by the World

The November 26 observations were collected by research scientist Bryce Bolin and his team using the Gemini Multi-Object Spectrograph at Maunakea. But here's the unusual part: they weren't alone. Students from around the world joined the observing session remotely, watching in real time as astronomers tracked this rare visitor. It's part of a program called Shadow the Scientists, which lets the public sit in on actual research using some of Earth's most powerful telescopes.

The images themselves are made from four separate exposures taken through different colored filters—blue, green, orange, and red. As the telescope held the comet steady in its field of view, background stars appeared to drift, creating colorful streaks across the frame. The effect is a technical necessity of how the telescope works, but it also makes the comet's isolation stand out: one steady point while the universe moves around it.

What happens next is still an open question. As 3I/ATLAS continues its journey away from the sun, it will cool down. But comets don't always respond immediately to heat—sometimes the warmth takes weeks or months to penetrate deep into the interior, triggering new outbursts or changes in composition. Gemini will keep watching, tracking how the comet's gases shift and whether it experiences any sudden eruptions as it leaves the solar system's influence.

This is only the third interstellar object ever detected passing through our corner of space. The first was 'Oumuamua in 2017, a mysterious visitor that sparked years of debate about its origin. Having a second one gives astronomers a chance to compare notes, to see whether these visitors follow patterns or whether each one is genuinely strange in its own way. And this time, thousands of people got to watch the observation happen live—a small but meaningful shift in how science gets done.