04/23/2026
One of our comet observers let us know:
3I/ATLAS has dominated the comet news in the past year, and JCMT was prominently involved in the submillimeter observing effort.
We (Kuan et Coulson et al) were first to detect hydrogen cyanide in its coma.
This occurred early September 2025 when 3I was 2.1 AU from the Sun.
In December and January, post-perihelion, we observed strong methanolvemissions, enabling us to determine that the abundance of methanol compared to water was several times larger than has ever been measured in Solar System
comets, and that the temperature of the gas in the coma was a very cold 20 K.
Emission line widths were extremely (and, in a sense, commensurately) narrow;
3I/ATLAS has been in the deep-freeze for the past 10 billion years, after all!
We also detected carbon monoxide while other observers detected formaldehyde, amongst other organic chemicals.
All the chemicals mentioned are common in Solar System comets.
- Two 'telegrams' were issued at the time (CBET 5608 and CBET 5628), the HCN detection was reported in MNRAS (Vol 546, p1) , and a further paper is in preparation.
Thanks to Iain Coulson!