Monster Oort Cloud Comet Observed in the Outer Solar System

Comet C/2014 UN271 is one of the largest Oort Cloud comets ever observed, measuring 140 km across. It’s currently at a distance of 16.5 AU from the Sun, which makes it tough to observe with all but the largest telescopes. Astronomers have used ALMA in Chile to observe the comet, watching as jets of carbon monoxide gas are erupting from its nucleus. This is a surprising level of activity for a comet that’s so far from the Sun.