26P/Grigg–Skjellerup

26P/Grigg–Skjellerup
Comet Grigg–Skjellerup photographed from the European Southern Observatory on 29 June 1992
Discovery
Discovered byJohn Grigg
John Francis Skjellerup
Discovery date23 July 1902
17 May 1922
Designations
  • P/1808 C1, P/1902 O1
  • P/1922 K1, P/1927 F1
  • 1808 III, 1902 II, 1922 I
  • 1927 V, 1932 II, 1937 III
  • 1942 V, 1947 II, 1952 IV
  • 1957 I, 1961 IX, 1967 I
  • 1972 II, 1977 VI, 1982 IV
  • 1987 X, 1992 XVIII
Orbital characteristics[4][5]
Epoch17 October 2024 (JD 2460600.5)
Observation arc216.67 years
Earliest precovery date6 February 1808[1]
Number of
observations		827
Aphelion4.947 AU
Perihelion1.084 AU
Semi-major axis3.015 AU
Eccentricity0.64056
Orbital period5.236 years
Max. orbital speed36.6 km/s[2]
Inclination22.433°
211.54°
Argument of
periapsis		2.136°
Mean anomaly55.845°
Last perihelion25 December 2023
Next perihelion18 March 2029[3]
TJupiter2.804
Earth MOID0.085 AU
Jupiter MOID0.006 AU
Physical characteristics
Mean radius
1.3 km (0.81 mi)[6]
12 hours[7]
(V–R) = 0.42±0.10[7]
Comet total
magnitude (M1)		16.5

Comet Grigg–Skjellerup (formally designated 26P/Grigg–Skjellerup) is a periodic comet. It was visited by the Giotto probe in July 1992.[8] The spacecraft came as close as 200 km, but could not take pictures because some instruments were damaged from its encounter with Halley's Comet.[9] The comet last came to perihelion (closest approach to the Sun) on 25 December 2023,[5][2][10] but was 1.8 AU from Earth and only 31 degrees from the Sun.[2]

Observational history

The comet was discovered in 1902 by John Grigg of New Zealand, and rediscovered in its next appearance in 1922 by John Francis Skjellerup, an Australian then living and working for about two decades in South Africa where he was a founder member of the Astronomical Society of Southern Africa. In 1987, it was belatedly discovered by Ľubor Kresák that the comet had been observed in 1808 as well, by Jean-Louis Pons. Pons observed the comet on 6 and 9 February, which was insufficient to calculate an approximate orbit.[1]

In 1972 the comet was discovered to produce a meteor shower, the Pi Puppids, and its current orbit makes them peak around 23 April, for observers in the southern hemisphere, best seen when the comet is near perihelion.

During the comet's 1982 approach it was detected using radar by the Arecibo Observatory.[11]

The apparition of 2002 was very unfavorable due to solar conjunctions, thus no observations were conducted at that time.[12][5]

Orbit

The comet has often suffered the gravitational influence of Jupiter, which has altered its orbit considerably. For instance, its perihelion distance has changed from 0.77 AU in 1725 to 0.89 AU in 1922 to 0.99 AU in 1977 and to 1.12 AU in 1999.

Physical characteristics

The comet nucleus is estimated to be 2.6 km (1.6 mi) in diameter.[6] Light-curve analysis from the Giotto flyby in 1992 revealed that Grigg–Skjellerup is surprisingly an old comet compared to 1P/Halley, suggesting that 26P is estimated to be around 89 comet-years in age.[12] Ground-based photometry of the comet reveal a non-spherical nucleus with a rotation period longer than 12 hours.[7]

The comet is a type locality for the mineral brownleeite.[13][14]

Exploration

Main article: Giotto (spacecraft)

In 1987, Grigg–Skjellerup was selected as the second comet targeted by the Giotto mission due to its perihelion in 1992 occurring very close to the Earth's orbit itself.[15]

By February 1990, the mission control at the European Space Agency reactivated the spacecraft after four years of hibernation following the Halley mission, subsequently executing the first ever Earth flyby in space exploration history to reach 26P on July 1990.[16] Giotto reached Grigg–Skjellerup on 10 July 1992 at a distance of 200 km (120 mi), much closer than its approach to Halley's Comet, but was unable to obtain images as its camera was destroyed during the Halley rendezvous in 1986. Despite this, the spacecraft was able to measure the interaction of the solar wind and how it affects the coma of this comet.[17]

Giotto was deactivated just 13 days after its flyby of Grigg–Skjellerup on 23 July 1992.

Cancelled proposals

Not to be confused with International Cometary Explorer.

In 1972, a NASA spacecraft mission based from the Explorer 47/50 satellite called Cometary Explorer was proposed to intercept Grigg–Skjellerup at a distance of 1,000 km (620 mi) by April 1977,[18] with an option to flyby 21P/Giacobini–Zinner on a potential mission extension in 1979.[19] This would serve as a precursor mission for an eventual mission to Halley in 1986,[18] however it was rejected due to budget cuts.[19]

See also

References

  1. ^ a b L. Kresak (1987). "The 1808 Apparition and the Long-Term Physical Evolution of Periodic Comet Grigg Skjelierup". Bulletin of the Astronomical Institutes of Czechoslovakia. 38 (2): 65–75. Bibcode:1987BAICz..38...65K. ISSN 0004-6248.
  2. ^ a b c "Horizons Batch for 26P/Grigg-Skjellerup (90000377) on 2023-Dec-25" (Perihelion occurs when rdot flips from negative to positive). JPL Horizons. Archived from the original on 16 February 2023. Retrieved 11 February 2023. (JPL#K234/7 Soln.date: 2022-Dec-19)
  3. ^ "Horizons Batch for 26P/Grigg-Skjellerup (90000377) on 2029-Mar-18" (Perihelion occurs when rdot flips from negative to positive). JPL Horizons. Retrieved 26 September 2025. (JPL#K234/25 Soln.date: 2024-Oct-11)
  4. ^ "26P/Grigg–Skjellerup – JPL Small-Body Database Lookup". ssd.jpl.nasa.gov. Jet Propulsion Laboratory. Retrieved 29 September 2020.
  5. ^ a b c "26P/Grigg–Skjellerup Orbit". Minor Planet Center. Retrieved 16 June 2014.
  6. ^ a b P. L. Lamy; I. Toth; Y. R. Fernández; H. A. Weaver (2004). "The Sizes, Shapes, Albedos, and Colors of Cometary Nuclei" (PDF). Comets II. pp. 223–264. Bibcode:2004come.book..223L. JSTOR j.ctv1v7zdq5.22.
  7. ^ a b c H. Boehnhardt; N. Rainer; K. Birkle; G. Schwehm (1999). "The nuclei of comets 26P/Grigg–Skjellerup and 73P/Schwassmann–Wachmann 3". Astronomy & Astrophysics. 341: 912–917. Bibcode:1999A&A...341..912B.
  8. ^ "Giotto, ESA's first deep-space mission: 25 years ago". European Space Agency. 11 March 2011. Archived from the original on 17 October 2011.
  9. ^ "Giotto's second comet encounter". European Space Agency. 10 March 2006. Archived from the original on 19 January 2012.
  10. ^ Kinoshita, Kazuo (3 July 2018). "26P/Grigg-Skjellerup past, present and future orbital elements". Comet Orbit. Archived from the original on 20 May 2011. Retrieved 24 July 2023.
  11. ^ J. K. Harmon; D. B. Campbell; S. J. Ostro; M. C. Nolan. "Radar Observations of Comets" (PDF). Planetary and Space Science. 47 (12): 1409–1422. Bibcode:1999P&SS...47.1409H. doi:10.1016/S0032-0633(99)00068-9.
  12. ^ a b I. Ferrin (2007). "Secular light curve of Comet 28P/Neujmin 1 and of spacecraft target Comets 1P/Halley, 9P/Tempel 1, 19P/Borrelly, 21P/Giacobinni–Zinner, 26P/Grigg–Skjellerup, 67P/Churyumov–Gerasimenko, and 81P/Wild 2". Icarus. 191 (2): 22–44. Bibcode:2007Icar..191S..22F. doi:10.1016/j.icarus.2005.05.023.
  13. ^ "Comet 26P/Grigg-Skjellerup, Outer Space". www.mindat.org. Archived from the original on 20 May 2017. Retrieved 3 April 2017.
  14. ^ "NASA Finds New Type of Comet Dust Mineral". www.nasa.gov. 12 June 2008. Retrieved 3 April 2017.
  15. ^ R. Reinhard (September 1987). The Giotto Extended Mission. Proceedings of the International Symposium on the Diversity and Similarity of Comets. Noordwijk, Netherlands. pp. 523–529. Bibcode:1987ESASP.278..523R.
  16. ^ H. R. Nye; A. Morani (1993). "The Giotto Extended Mission (GEM) – High risk, high payoff". ESA Bulletin. ISSN 0376-4265.
  17. ^ M. G. Lebedev (2000). "Comet Grigg–Skjellerup Atmosphere Interaction With the Oncoming Solar Wind". Astrophysics and Space Science. 274 (1/2): 221–230. Bibcode:2000Ap&SS.274..221L. doi:10.1023/A:1026568511203.
  18. ^ a b R. W. Farquhar; N. F. Ness (1972). Early missions to comets (PDF) (Report). NASA / GSFC. NASA-TM-X-66026.
  19. ^ a b P. Butler; et al. (1973). System definition for Cometary Explorer: A mission to intercept the comets Grigg-Skjellerup (1977) and Giacobini-Zinner (1979) (PDF) (Report). NASA / GSFC. NASA-TM-X-70561.
  20. ^ N. Stephenson (2015). "Pioneers and Prospectors". Seveneves: A Novel. Harper Collins. pp. 416–418. ISBN 978-0-062-19041-3.


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