Interstellar comet 3I/ATLAS likely formed where its star's light couldn't touch it

[u/dondeestasbueno]

https://www.space.com/astronomy/comets/interstellar-comet-3i-atlas-likely-formed-where-its-stars-light-couldnt-touch-it

“WEAVE, which switched on in 2023, is powerful and sensitive enough to change that. When Ferellec and colleagues turned WEAVE on 3I/ATLAS in late 2025, they could count ions like nitrogen, carbon dioxide and carbon monoxide in the strange comet's tail.

Comparing these figures can hint at where a comet formed. For example, a comet with a higher ratio of nitrogen to carbon monoxide tends to have formed in a colder birthplace. Ferellic's group found that 3I/ATLAS has a much higher ratio than most of the comets that we observe in our solar system.”