78P/Gehrels
78P/Gehrels, also known as Gehrels 2, is a Jupiter-family periodic comet in the Solar System with a current orbital period of 7.22 years.
| Discovery | |
|---|---|
| Discovered by | Tom Gehrels |
| Discovery date | September 29, 1973 |
| Designations | |
Alternative designations | 1973 XI; 1981 XVII; 1989 XVII |
| Orbital characteristics | |
| Epoch | March 6, 2006 |
| Aphelion | 5.462 AU |
| Perihelion | 2.009 AU |
| Semi-major axis | 3.735 AU |
| Eccentricity | 0.4622 |
| Orbital period | 7.22 yr |
| Inclination | 6.2530° |
| Last perihelion | April 2, 2019 January 12, 2012 October 27, 2004 |
| Next perihelion | 2026-06-25 |
It was discovered by Tom Gehrels at the Lunar and Planetary Laboratory, Arizona, USA on photographic plates exposed between 29 September and 5 October 1973 at the Palomar Observatory. It had a brightness of apparent magnitude of 15. Brian G. Marsden computed the parabolic and elliptical orbits which suggested an orbital period of 8.76 years, later revising the data to give a perihelion date of 30 November 1963 and orbital period of 7.93 years.
The comet's predicted next appearance in 1981 was observed by W. and A. Cochran at the McDonald Observatory, Texas on 8 June 1981. It was observed again in 1989 and in 1997, when favourable conditions meant that brightness increased to magnitude 12. It has subsequently been observed in 2004 when it reached magnitude 10, 2012, and 2018.