78P/Gehrels

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78P/Gehrels
78P 2019-01-27 image ZTF-sso-446-zr-fov-5.6arcmin.png
Comet Gehrels 2 photographed from the Zwicky Transient Facility on 27 January 2019
Discovery [1]
Discovered by Tom Gehrels
Discovery site Palomar Observatory, Arizona, USA
Discovery date29 September 1973
Designations
P/1973 S1, P/1981 L1
  • 1973 XI, 1981 XVII
  • 1989 XVII
  • 1973n, 1981f, 1989n
Orbital characteristics [2] [3]
Epoch 21 November 2025 (JD 2461000.5)
Observation arc 52.247 years
Number of
observations		8,640
Aphelion 5.461 AU
Perihelion 2.005 AU
Semi-major axis 3.733 AU
Eccentricity 0.46299
Orbital period 7.212 years
Inclination 6.257°
210.49°
Argument of
periapsis 		192.78°
Mean anomaly 330.47°
Last perihelion2 April 2019 [4] [5]
Next perihelion25 June 2026
TJupiter 2.887
Earth MOID 1.022 AU
Jupiter MOID 0.024 AU
Physical characteristics [2]
Mean radius
4.28 km (2.66 mi) [6]
Comet total
magnitude (M1)		9.1
Comet nuclear
magnitude (M2)		12.5

78P/Gehrels, also known as Gehrels 2, is a Jupiter-family comet with a current orbital period of 7.22 years. It is the second periodic comet discovered by American astronomer, Tom Gehrels

Contents

Observational history

It was discovered by Tom Gehrels at the Palomar Observatory, Arizona, USA on photographic plates exposed between 29 September and 5 October 1973 at the Palomar Observatory. [1] 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. [7]

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. [7] It has subsequently been observed on every apparition since. [4]

Orbit

Comet 78P/Gehrels' aphelion at a distance of 5.4 AU (810 million km) from the Sun meant that its orbit is frequently perturbed by Jupiter. [2] On 15 September 2029, the comet will pass within 0.018 AU (2.7 million km) of Jupiter and be strongly perturbed. [2] By the year 2200, the comet will have a centaur-like orbit with a perihelion (closest distance to the Sun) near Jupiter at . [8] This outward migration from a perihelion of 2.01 AU (301 million km) to 5.057 AU (756.5 million km) could cause the comet to go dormant.

The Outward Migration of 78P/Gehrels
Year (epoch)2009 [2] 20302200 [8]
Semi-major axis 3.736.029.37
Perihelion 2.004.084.99
Aphelion5.467.9613.7
Comet 78P passing within 0.018 AU (2.7 million km) of Jupiter in 2029. Comet78P2029.png
Comet 78P passing within 0.018 AU (2.7 million km) of Jupiter in 2029.

References

  1. 1 2 T. Gehrels; R. Adams; C. Vesely; et al. (31 October 1973). B. G. Marsden (ed.). "Comet Gehrels (1973n)". IAU Circular. 2589 (1). Bibcode:1973IAUC.2589....1G.
  2. 1 2 3 4 5 6 "78P/Gehrels 2 – JPL Small-Body Database Lookup". ssd.jpl.nasa.gov. Jet Propulsion Laboratory . Retrieved 11 May 2009.
  3. ↑ "78P/Gehrels Orbit". Minor Planet Center . Retrieved 29 June 2020.
  4. 1 2 S. Yoshida (3 October 2006). "78P/Gehrels 2". www.aerith.net. Retrieved 24 February 2010.
  5. ↑ S. Nakano (10 June 2011). "78P/Gehrels 2 (NK 2102)". OAA Computing and Minor Planet Sections. Retrieved 18 February 2012.
  6. ↑ C. S. Snodgrass; S. C. Lowry; A. Fitzsimmons (2007). "Optical observations of 23 distant Jupiter Family Comets, including 36P/Whipple at multiple phase angles" (PDF). Monthly Notices of the Royal Astronomical Society. 385 (2): 737–756. arXiv: 0712.4204 . Bibcode:2008MNRAS.385..737S. doi: 10.1111/j.1365-2966.2008.12900.x . S2CID   55536237.
  7. 1 2 Kronk, Gary W. "78P/Gehrels 2". Cometography. Retrieved 25 February 2015.
  8. 1 2 "Barycentric Osculating Orbital Elements for Comet 78P/Gehrels 2 in epoch 1800 and 2200". JPL Horizons On-Line Ephemeris System . Jet Propulsion Laboratory . Retrieved 11 May 2009. (Solution using the Solar System's barycenter (Sun+Jupiter). Select Ephemeris Type:Elements and Center:@0) }}
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