Interstellar comet 3I/ATLAS likely formed where its star's light couldn't touch it
In late 2025, astronomers were able to analyze charged particles in the tail of interstellar comet 3I/ATLAS, revealing it contains more nitrogen than typical comets from our solar system. This finding suggests that 3I/ATLAS likely formed in extremely cold conditions far from its home star, as Lea Ferellec, a research fellow at Northumbria University, explained.
The team used the William Herschel Telescope's WEAVE instrument in Spain's Canary Islands to perform spectroscopy, which splits incoming light into its spectrum, allowing them to identify chemical elements and their fingerprints. By comparing the nitrogen to carbon monoxide ratio in 3I/ATLAS' tail, the researchers estimated that the comet formed somewhere colder than -240°C.
This discovery provides a rare opportunity to study material from a distant star system, helping scientists better understand how planets form around other stars.
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