3I/ATLAS Mystery: Oxford Professor Reveals Interstellar Comet From A Dead Star

In the velvet darkness of our cosmic backyard, a ghost has appeared—and it may be older than the stars we know. Discovered on 1 July 2025 by the Asteroid Terrestrial-impact Last Alert System (ATLAS) in Río Hurtado, Chile, the interstellar comet known as 3I/ATLAS is not just a visitor; it is a time capsule from a forgotten era.

While our own solar system is a relatively youthful 4.6 billion years old, this icy wanderer is estimated to be between 8 and 14 billion years old. To put that into perspective, 3I/ATLAS may have begun its journey before our Sun even ignited, potentially originating from a star that has long since flickered out and died.

For Associate Professor Michele Bannister, an astrophysicist at the University of Canterbury (UC), this is the moment she has spent her entire career preparing for. Speaking to Astrobiology, Bannister described the comet as a 'once in a lifetime opportunity' and a 'calling card from the past.'

After the mysterious 'Oumuamua in 2017 and 2I/Borisov in 2019, 3I/ATLAS is the third confirmed interstellar object to come to Earth. It lets us see the chemistry of old, faraway planetary systems in a way that isn't common. The object was about 420 million miles (670 million km) from the Sun when it was found, and it was already showing signs of activity that set it apart from other objects that had been found before it.

The Ancient Origin Of The 3I/ATLAS 'Dusty Snowball'

The discovery has caused a lot of excitement in the scientific community, mostly because of the work of the UC team and Professor Chris Lintott at the University of Oxford. Researchers were able to figure out the comet's incredible age based on its high speed by using the 'Ōtautahi-Oxford model,' which is a theoretical framework for tracking the movements and origins of interstellar objects. The comet came into our system at a hyperbolic excess velocity of 58 km/s (about 130,000 mph), which is much faster than any object that is held by the Sun's gravity.

'That's the great joy of interstellar objects,' Bannister explained. 'They're giving us clues, because they're made up of the building blocks of planet formation elsewhere in the galaxy.' The fact that 3I/ATLAS likely formed around a star in the Milky Way's 'thick disk'—a region populated by the galaxy's oldest inhabitants—suggests it carries the chemical signatures of a prehistoric universe.

Bannister affectionately refers to the object as a 'dusty wee snowball,' a nod to its composition of ice and dust that reflects the sun's rays. However, Hubble Space Telescope observations have refined our understanding of its scale, placing the diameter of the nucleus between 440 metres and 3.5 miles. As it breached our skies, it revealed an 'unusually rich atomic nickel and iron emission,' a chemical fingerprint that speaks volumes about the extreme environment in which it was forged billions of years ago.

Deciphering The Two Tails Of 3I/ATLAS

What makes this visitor particularly striking is its visual profile. Unlike local comets, 3I/ATLAS sports a dual-tail structure: a traditional dust tail and a rarer 'anti-tail' that appears to point directly toward the Sun. This phenomenon, while occasionally seen in domestic comets, is providing critical data for the Ōtautahi-Oxford model.

The anti-tail is formed by larger debris particles that are less affected by solar radiation pressure, creating the illusion of a sunward spike. These tails are not just aesthetic; they are the comet's way of 'talking' to us, shedding material that allows scientists to measure its rotation and thermal properties.

The clock, however, is ticking. 'We only have a few hundred days to try and interpret what it's telling us,' Bannister warned. Following its closest approach to the Sun (perihelion) on 29 October 2025 at a distance of 1.36 AU, the comet passed 168 million miles from Earth on 19 December. Because it is travelling on a hyperbolic trajectory, 3I/ATLAS is not bound by our Sun's gravity. It is merely passing through, moving far too fast to ever be captured.

After it leaves our neighborhood, it will disappear into the empty space between stars, taking its secrets with it. For now, scientists all over the world are working hard to gather as much information as they can.

3I/ATLAS is teaching us that the building blocks of worlds are the same everywhere, but they are also older than we can imagine. It is a haunting reminder that we are part of a much bigger, older, and more mysterious story that started in the heart of a star that may no longer exist.