What is Known about Comet Wirtanen?
Studies of comet Wirtanen over the past few apparitions have revealed some of the characteristics of the nucleus, though much is still unknown. Best estimates of some properties are listed here.
Nucleus Physical Properties
| Property | Value | Reference |
|---|---|---|
| Effective Radius | 0.56 km | Boehnhardt et al (2002) A&A 387, 1107-1113 |
| 0.7 km | Howell et al.; Radar measurements from 10-18 Dec 2018 | |
| Axial Ratio (prolate ellipsoid) | >1.4 | Boehnhardt et al (2002) A&A 387, 1107-1113 |
| Rotation Period | 7.6 hr 6.0 hr | Meech et al (1997) A&A 326, 1268-1276 |
| 6.0 hr | Lamy et al. (1998) A&A 335, L25-29 | |
| 8.91 hr | Farnham et al. (2018) CBET 4571 | |
| 9.2 hr | Jehin et al. (2018) CBET 4585 | |
| Spin Axis | Unknown | |
| Peak Water Production | 1.3×1028 molec/s | Groussin & Lamy (2003) A&A 412, 879-891 |
| 1.7×1028 molec/s | Kobayashi & Kawakita (2010) Pub. Ast. Soc. Japan 62, 1025-1033 | |
| 7.2×1027 molec/s | D.G. Schleicher, measured 16 Dec 2018 | |
| Peak Afρ | 150 cm | Average of many measurements |
| 117 cm | D.G. Schleicher, measured 16 Dec 2018 | |
| Active Fraction | 100% | Groussin & Lamy (2003) A&A 412, 879-891 |
Other Phenomena
- Radar measurements from 10-18 Dec 2018 detected large grains (~2 cm) in the coma.
- Earliest solid detection of coma is at 3.3 AU inbound
- Possible outbursts were seen in 2002 and 2008.
- Samarasinha et al. (Planet Space Sci 44, 275-281, 1996) suggest that the nucleus is likely in non-principal axis rotation.