3I/ATLAS Update: Gemini North Captures Interstellar Guest Emitting Reactive Carbon

In a cosmic game of hide and seek, our third-ever known visitor from another star system is finally revealing its true colours. For months, astronomers have been tracking a mysterious wanderer known as 3I/ATLAS, a visitor that has travelled across the unimaginable void of interstellar space just to graze the edges of our Sun.

While most of us were looking at the familiar stars, this frozen relic was undergoing a dramatic chemical transformation, shifting from a dull, dusty red to a vibrant, ghostly green. It is a spectacle that reminds us how little we truly know about the space beyond our backyard.

The Galactic Traveller: What New Glows Reveal About 3I/ATLAS

First detected on 1 July 2025 by the Asteroid Terrestrial-impact Last Alert System (ATLAS), 3I/ATLAS has been under the relentless gaze of the world's most powerful instruments. From the Hubble Space Telescope and the James Webb Space Telescope to the Very Large Telescope, every major observatory has taken a turn documenting its hyperbolic flight.

The comet reached its solar conjunction on 21 October and made its closest approach to the Sun on 29 October at a distance of roughly 12.9 million miles (0.139 AU). However, it is the recent images from the Gemini North Telescope on Maunakea, Hawaii, that have sparked the most excitement.

When the comet was first imaged by Gemini South in Chile back in September, it appeared with a distinct red hue. Now, as it retreats from its fiery encounter with the Sun, it has developed a faint green glow. This isn't just a trick of the light; it is a direct result of the Sun's heat penetrating the comet's icy core. As the temperature rises, diatomic carbon—an extremely reactive substance common in cometary bodies—evaporates and emits that signature emerald radiance.

The speed of this object is equally staggering. While it slowed down slightly after passing the Sun due to gravitational pull, it remains on a trajectory to escape our Solar System entirely. It is moving significantly faster than its famous predecessors, 1I/'Oumuamua and 2I/Borisov, clocking speeds of approximately 150,000 miles per hour (67 km/s), making it the most energetic interstellar object (ISO) we have ever recorded.

Shadowing the Scientists: Public Access to 3I/ATLAS Observations

Perhaps the most human element of this story is how we are watching it. Rather than keeping the data locked behind university doors, a programme called Shadow the Scientists is bringing the public into the control room. Led by Bryce Bolin, a research scientist from Eureka Scientific, the initiative invites students from Hawaii and Chile to join astronomers via live Zoom sessions. These budding scientists get to watch in real time as the massive telescopes are manoeuvred and data is harvested.

'Sharing an observing experience in some of the best conditions available gives the public a truly front-row view of our interstellar visitor,' Bolin remarked. He noted that allowing people to see the raw process helps to demystify science, providing transparency to the study of such a 'fascinating object.'

The mystery of 3I/ATLAS is far from solved. While nickel has been detected in the comet, iron—which usually appears in equal measure—is curiously absent. Astronomers are hopeful that as the heat continues to soak into the nucleus, the iron will finally make an appearance.

This absence is particularly baffling because most Solar System comets maintain a 1:1 ratio of these two metals; the lack of iron suggests 3I/ATLAS may have formed in a vastly different chemical environment than our own planets.

Looking ahead, the scientific community is already planning for the next visitor. While it is currently impossible to launch a mission to catch an ISO once it is spotted, concepts for a 'comet interceptor' are in the works by the European Space Agency (ESA), scheduled for launch in 2029.

These spacecraft would sit in orbit at the Sun-Earth L2 Lagrange point, waiting for the Vera Rubin Observatory and its Legacy Survey of Space and Time (LSST) to flag a new arrival. With estimates suggesting we could find at least ten more objects like 3I/ATLAS in the near future, the era of interstellar exploration is only just beginning.

As 3I/ATLAS begins its long journey back into the infinite darkness of interstellar space, it leaves behind more questions than answers about the chemical makeup of other star systems. The absence of iron and the dramatic shift to a vibrant green glow suggest that our celestial visitor is far more alien than we first imagined.