78P/Gehrels
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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.
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.[1]
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.[1] It has subsequently been observed in 2004 when it reached magnitude 10, 2012, and 2018.[2]
Outward migration
Comet 78P/Gehrels' aphelion (furthest distance from the Sun) of 5.4AU[3] is in the zone of control of the gas giant Jupiter and the orbit of the comet is frequently perturbed by Jupiter.[4] On September 15, 2029, the comet will pass within 0.018 AU (2.7 million kilometers) of Jupiter[4] and be strongly perturbed. By the year 2200, the comet will have a centaur-like orbit with a perihelion (closest distance to the Sun) near Jupiter.[5] This outward migration from a perihelion of 2AU to a perihelion of ~5AU could cause the comet to go dormant.
| Year (epoch) | 2009[3] | 2030 | 2200[5] |
|---|---|---|---|
| Semi-major axis | 3.73 | 6.02 | 9.37 |
| Perihelion | 2.00 | 4.08 | 4.99 |
| Aphelion | 5.46 | 7.96 | 13.7 |
See also
References
External links
- Template:JPL Small Body
- 78P/Gehrels – Minor Planet Center
- 78P/Gehrels 2 (2012)
- 78P at Kronk's Cometography
- Lightcurve (Artyom Novichonok)
- 78P as seen by 10" GRAS-04 on 2011-05-03 (120 sec x 6)
- 78P as seen by Template:Convert Schmidt-Cassegrain on 2011 08 06 (3 x 748 sec) and 2011 08 09 (6 x 600 sec)
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