78P/Gehrels

78P/Gehrels
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

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.^[6]

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.^[6] It has subsequently been observed in 2004 when it reached magnitude 10, 2012, and 2018.^[1]

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