We just spotted the third comet ever to visit our solar system from another star.
March 25, 2026
Original Paper
Perihelion observations of interstellar comet 3I/ATLAS with the IRAM 30-m telescope
arXiv · 2603.23240
The Takeaway
Following the famous 'Oumuamua and Borisov, this new visitor from another star system, 3I/ATLAS, provides a rare chance to study the chemistry of a different sun. Its unusual gas expansion suggests it might be shedding heavy molecules or icy grains as it approaches our Sun.
From the abstract
3I/ATLAS is the third interstellar comet identified as passing through the Solar System. Its high outgassing activity and favourable perihelion passage on October 29, 2025 UT provided an excellent opportunity to investigate the composition of its coma gases through millimeter spectroscopy. We present observations undertaken with the IRAM 30-m telescope on November 1--3, 2025 at an heliocentric distance of 1.36--1.37 au. Lines of HCN, CH$_3$OH, CO, and H$_2$CO are well detected, and $\sim$4$\sigm