Research conducted by astronomer Matthew Hopkins and his team at Oxford University suggests that 3i/Atlas, the second interstellar comet discovered near our solar system, may have been on its trajectory over 3 billion years ago.
Top view of the Milky Way displaying the predicted orbits of our Sun and 3i/Atlas. Comets are represented by dashed red lines, while the sun is indicated by a dashed yellow line. The comet’s route to the outer thick disc is mostly clear, whereas the sun remains close to the nucleus of the galaxy. Image credit: M. Hopkins / Otautahi Oxford Team / ESA / Gaia / DPAC / Stefan Payne-Wardenaar / CC-SA 4.0.
“All comets formed alongside our solar system, like Halley’s comets, are up to 4.5 billion years old,” Dr. Hopkins explained.
“In contrast, interstellar visitors can be significantly older. Our statistical analyses indicate that 3i/Atlas is very likely to be the oldest comet we’ve observed thus far.”
Unlike 1i/Oumuamua and 2i/Borisov, the two previous interstellar objects that passed through our solar system, 3i/Atlas appears to be on a more inclined path through the Milky Way.
A recent study forecasts that 3i/Atlas is likely to be rich in water ice, as it probably formed around the star of the ancient, thick disc.
“This is an aspect of the galaxy that we’ve never encountered before,” said Chris Lintot, a professor at Oxford University and host of The Sky at Night.
“I believe there is a two-thirds chance that this comet predates the solar system and has been drifting through interstellar space ever since.”
As it nears the Sun, the heat from sunlight activates 3i/Atlas, generating a coma and tail composed of steam and dust.
Initial observations indicate that the comet is already active and may even be larger than any of its interstellar predecessors.
If this is validated, it could influence the detection of similar objects by future telescopes, such as the upcoming Vera C. Rubin Observatory.
Furthermore, it could offer insights into the role that ancient interstellar comets play in the formation of stars and planets throughout the galaxy.
“We’re in an exciting phase. 3i/Atlas is already displaying signs of activity,” remarked Dr. Michele Bannister, an astronomer at the University of Canterbury.
“The gases we might observe in the future, as 3i/Atlas is heated by the Sun, will help us evaluate our models.”
“Some of the world’s largest telescopes are currently monitoring this new interstellar entity. One of them may make a significant discovery!”
The astronomers presented their findings today at the National Astronomical Conference of the Royal Astronomical Society 2025 in Durham, England.
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Matthew Hopkins et al. Intergalactic interstellar object population in LSST. NAM 2025
Source: www.sci.news
