78P/Gehrels
{{short description|Periodic comet with 7 year orbit}}
{{Infobox comet
| name=78P/Gehrels
| image=78P 2019-01-27 image ZTF-sso-446-zr-fov-5.6arcmin.png
| discoverer=Tom Gehrels
| discovery_date=September 29, 1973
| designations=1973 XI; 1981 XVII; 1989 XVII
| epoch=March 6, 2006
| semimajor=3.735 AU
| perihelion=2.009 AU
| aphelion=5.462 AU
| eccentricity=0.4622
| period=7.22 yr
| inclination= 6.2530°
| last_p=April 2, 2019
January 12, 2012
October 27, 2004
}}
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.
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.
Outward migration
Comet 78P/Gehrels' aphelion (furthest distance from the Sun) of 5.4AU is in the zone of control of the gas giant Jupiter and the orbit of the comet is frequently perturbed by Jupiter. On September 15, 2029, the comet will pass within 0.018 AU (2.7 million kilometers) of Jupiter 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. This outward migration from a perihelion of 2AU to a perihelion of ~5AU could cause the comet to go dormant.
| class=wikitable style="text-align:center"
|+ The Outward Migration of 78P/Gehrels !Year (epoch)!!2009!!2030!!2200 | |||
| Semi-major axis | 3.73 | 6.02 | 9.37 |
| Perihelion | 2.00 | 4.08 | 4.99 |
| Aphelion | 5.46 | 7.96 | 13.7 |
File:Comet78P2029.png of Jupiter in 2029.]]
See also
References
{{Reflist|refs=
|date=2006-10-03
|title=78P/Gehrels 2
|publisher=Seiichi Yoshida's Comet Catalog
|author=Seiichi Yoshida
|url=http://www.aerith.net/comet/catalog/0078P/index.html
|access-date=2010-02-24}}
|title=78P/Gehrels Orbit
|url=https://www.minorplanetcenter.net/db_search/show_object?object_id=78P
|publisher=Minor Planet Center
|access-date=2020-06-29}}
|date=2009-04-20
|title=78P/Gehrels 2 (NK 1760)
|publisher=OAA Computing and Minor Planet Sections
|author=Syuichi Nakano
|author-link=Syuichi Nakano
|url=http://www.oaa.gr.jp/~oaacs/nk/nk1760.htm
|access-date=2010-02-24}}
|date=2011-06-10
|title=78P/Gehrels 2 (NK 2102)
|publisher=OAA Computing and Minor Planet Sections
|author=Syuichi Nakano
|author-link=Syuichi Nakano
|url=http://www.oaa.gr.jp/~oaacs/nk/nk2102.htm
|access-date=2012-02-18}}
|title= 78P/Gehrels 2
|first=Gary W |last=Kronk
|publisher= Cometography
|url= http://cometography.com/pcomets/078p.html
|access-date= 25 February 2015}}
|type=2011-05-21 last obs
|title=JPL Small-Body Database Browser: 78P/Gehrels 2
|url=http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=78P
|access-date=2009-05-11}}
|type=2006-02-26 last obs
|title=JPL Close-Approach Data: 78P/Gehrels 2
|url=http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=78P;cad=1#cad
|access-date=2009-05-11}}
|title=Orbital Elements of 78P/Gehrels in 2200
|author=Heider
|url=http://home.surewest.net/kheider/astro/78P2200.txt
|archive-url=https://web.archive.org/web/20150606092400/http://home.surewest.net/kheider/astro/78P2200.txt
|archive-date=2015-06-06
|url-status=dead
|access-date=2009-05-11}}
}}
External links
- {{JPL Small Body|id=1000030}}
- [https://www.minorplanetcenter.net/db_search/show_object?object_id=78P 78P/Gehrels] – Minor Planet Center
- [http://www.aerith.net/comet/catalog/0078P/2012.html 78P/Gehrels 2 (2012)]
- [http://cometography.com/pcomets/078p.html 78P at Kronk's Cometography]
- [https://web.archive.org/web/20110827020226/http://severastro.narod.ru/sla/com/lc/current/78p.gif Lightcurve] ([https://web.archive.org/web/20110528003850/http://severastro.narod.ru/sla/com/lc.htm Artyom Novichonok])
- 78P as seen by 10" [https://web.archive.org/web/20101230061406/http://wiki.global-rent-a-scope.com/GRAS_Telescopes.ashx GRAS-04] on [http://picasaweb.google.com/104133965506763777371/PICASA#5603186575585444690 2011-05-03] (120 sec x 6)
- 78P as seen by {{convert|0.3|m|in|adj=on}} Schmidt-Cassegrain on [https://www.flickr.com/photos/cbellh47/6015881842/ 2011 08 06] (3 x 748 sec) and [https://www.flickr.com/photos/cbellh47/6052745194/ 2011 08 09] (6 x 600 sec)
{{PeriodicComets Navigator|77P/Longmore|79P/du Toit–Hartley}}
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{{2019 in space}}
{{DEFAULTSORT:Gehrels, 078P}}