Free Astronomy Magazine September-October 2026

46 SEPTEMBER-OCTOBER 2026 ASTRO PUBLISHING I nterstellar comets are icy objects formed around a star other than the Sun that occasionally wander into our Solar System. “They are sort of fossils from a planetary formation process that happened very far away, but that we get the chance to study from much closer,” says astronomer Cyrielle Opitom, a researcher at the 3I/ATLAS might be older than the Sun by ESO Bárbara Ferreira T he above image of interstellar comet 3I/ATLAS was taken on 18 January 2026 with the FORS2 instrument on ESO’s Very Large Telescope (VLT). It is a stack of several images spanning 14 minutes. As the comet moves on the sky, the stars appear as trails in the background. [ESO/O. Hainaut] University of Edinburgh, United Kingdom. Together with Jean Man- froid and Damien Hutsemékers of the University of Liège, Belgium, Opitom led a study of 3I/ATLAS pub- lished in Nature Astronomy . 3I/ATLAS is the third interstellar ob- ject ever discovered, after 1I/ ‘ Oumua- mua and 2I/Borisov. It was found as it was approaching the Sun, spend- ing enough time in our Solar System for astronomers to study it in detail. While it was difficult to measure the composition of the first two inter- stellar objects — in the first as- tronomers didn’t detect gas and the