C/2016 R2 (PanSTARRS)
C/2016 R2 photographed from the Mount Lemmon Observatory on 16 January 2018. The comet's blue color comes from ionized carbon monoxide (CO+ ). | |
| Discovery | |
|---|---|
| Discovered by | Pan-STARRS |
| Discovery site | Haleakalā Observatory |
| Discovery date | 7 September 2016 |
| Orbital characteristics | |
| Epoch | 29 May 2018 (JD 2458267.5) |
| Observation arc | 1,762 days (4.82 years) |
| Number of observations | 4,319 |
| Aphelion | ≈1,600 AU (inbound) ≈1,100 AU (outbound) |
| Perihelion | 2.602 AU |
| Semi-major axis | ≈780 AU (inbound) ≈530 AU (outbound) |
| Eccentricity | 0.99631 |
| Orbital period | ≈22,000 years (inbound) ≈12,000 years (outbound) |
| Inclination | 58.224° |
| 80.569° | |
| Argument of periapsis | 33.192° |
| Mean anomaly | 0.001° |
| Last perihelion | 9 May 2018 |
| TJupiter | 1.060 |
| Earth MOID | 1.720 AU |
| Jupiter MOID | 2.117 AU |
| Physical characteristics | |
Mean diameter | 5–30 km (3–19 mi) |
| Comet total magnitude (M1) | 7.3 |
| Comet nuclear magnitude (M2) | 11.2 |
| 9.8 (2018 apparition) | |
C/2016 R2 (PanSTARRS), or simply C/2016 R2, is an unusual long-period comet that is extremely rich in carbon monoxide and nitrogen, but contains very little water. It was discovered on 7 September 2016 by the Pan-STARRS astronomical survey at Haleakalā Observatory in Hawaiʻi. The comet attracted attention from many astronomers as it approached its closest point to the Sun in May 2018 when it was inside of the asteroid belt at 2.6 AU. It has been observed to have a very complex tail. The comet nucleus is estimated to be 5–30 km (3–19 mi) in diameter.
Inbound, the comet orbited the Sun on a 22,000 year orbit, which took it out about 1600 AU. It was found to differ from typical comets, and was found to be rich in carbon monoxide (CO) but depleted in hydrogen cyanide (HCN), resulting in a blue coma. The blue color is thought to come from the rich amounts of carbon monoxide being ionized. The comet made its closest approach to the Sun in May 2018.