C/2016 R2 (PanSTARRS)

C/2016 R2 (PanSTARRS) is a comet discovered by the Pan-STARRS survey on September 7, 2016. It is notable for its unusual chemical composition, exhibiting strong emissions from carbon monoxide (CO+) and nitrogen ions (N2+) in its coma. This contrasts with many other comets, which are primarily dominated by water-ice outgassing. The presence of these volatile species suggests that C/2016 R2 (PanSTARRS) likely formed in a very cold region of the protoplanetary disk further away from the Sun than many other comets. Its perihelion occurred in May 2018, bringing it within approximately 2.7 astronomical units (AU) of the Sun. Observations of the comet have helped astronomers understand the distribution of volatile compounds in the early solar system and the origins of comets from different formation regions.