Briefly: The Astronomer’s Telegram posts quick, short, straightforward notices… like telegrams!
ATel#17416 www.astronomerstelegram.org/?read=17416
Farnham, T. L. Feaga, L. M. Ye, Q. et al. Observations of an Asymmetric CN Coma in Interstellar Comet 3I/ATLAS 23 Sep 2025; 19:02 UT
Cyanide and cyano-compounds are frequently found in comets- both carbon and nitrogen are abundant in the universe, and -CN molecules are one way to bind both elements into some stable form. Yet these compounds are small and light enough to boil and escape when heated, making them a part of the coma and tail. Also handy is that CN has spectral features that we can detect in our spectroscopes. In this case, Farnham et al. used time on the Lowell observatory to track CN from ATLAS. The CN emissions don’t form a nice, smooth shell around the nucleus, but instead lean towards the comet’s tail. This, the authors claim, is due to release of CN from both the nucleus, and secondhand, when particles shed by the comet continue to release volatiles as they drift into free space. We call this “hyperactivity”- a comet is, in effect, trailing off ‘micro-comets’ in a recursive activity pattern.