84P/Giclas
DiscovererHenry L. Giclas
Discovery siteLowell Observatory, USA
Discovery date8 September 1978
Mpc name
  • D/1931 R1,[1] P/1978 R2
  • P/1985 M1
Designations
  • 1978 XXII, 1985 XV
  • 1992 XXV, 1978k, 1985g
  • 1992l
Epoch21 November 2025 (JD 2461000.5)
Observation arc89.43 years
Earliest precovery date12 September 1931[2]
Obs1,792
Perihelion1.719 AU
Aphelion5.381 AU
Semimajor3.550 AU
Period6.689 years
Eccentricity0.51562
Inclination7.553°
Asc node108.08°
Arg peri281.74°
Mean293.89°
Tjup2.872
Earth moid0.862 AU
Jupiter moid0.555 AU
Mean radius0.90 ± 0.05 km (0.56 ± 0.031 mi)[3]
Albedo0.04 (assumed)
M 114.2
Last p3 June 2020
Next p12 February 2027[4]

84P/Giclas is a Jupiter-family comet with a 6.69-year orbit around the Sun. It is the only comet discovered by American astronomer, Henry L. Giclas.

Observational history

1931 apparition

It was announced in 1995 that Clyde W. Tombaugh had observed a previously unknown comet for three nights in September 1931.[2] Designated as D/1931 R1,[1] it was later confirmed to be an earlier apparition of 84P/Giclas upon reconstructing its orbit using non-gravitational accelerations in a 1996 study by Grzegorz Sitarski.[5]

1979 apparition

The comet was discovered by Henry L. Giclas from the Lowell Observatory on 8 September 1978.[6] At the time it was a diffuse 15th-magnitude object within the constellation Cetus.[a] He confirmed his discovery about two days later,[7] where Brian G. Marsden soon determined that it follows a 6.74-year periodic orbit around the Sun.[8] Throughout its 1978–1979 apparition, it remained mostly a photographic object.[9]

Follow-up observations

During the 2020 apparition, it was not more than 60 degrees from the Sun until September 2020. On 11 June 2033, the comet will pass 0.0387 astronomical units from the asteroid 4 Vesta.[10]

Physical characteristics

Based on observations by the Hubble Space Telescope in 1999–2000, the nucleus of the comet has a radius of 0.90 ± 0.05 km, assuming a geometric albedo of 0.04.[3]

Notes

  1. ^ Reported initial position upon discovery was: α = , δ = [9]

References

  1. ^ B. A. Skiff & D. H. Levy (1995-04-13). "Comet D/1931 R1". IAU Circular. 6161 (3). D. W. Green (ed.). ISSN 0081-0304
  2. ^ R. J. Bouma (1995-05-05). "Comet 84P/Giclas". IAU Circular. 6168 (4). D. W. Green (ed.). ISSN 0081-0304
  3. ^ P. L. Lamy; I. Toth; H. A. Weaver; M. F. A'Hearn; L. Jorda (2009). "Properties of the nuclei and comae of 13 ecliptic comets from Hubble Space Telescope snapshot observations". Astronomy & Astrophysics. 508 (2): 1045–1056. Bibcode:2009A&A...508.1045L. doi:10.1051/0004-6361/200811462. S2CID 125249770
  4. ^ "Horizons Batch for 84P/Giclas (90000868) on 2027-Feb-12" (Perihelion occurs when rdot flips from negative to positive). JPL Horizons. Retrieved 2022-06-19. (JPL#49 Soln.date: 2021-Mar-29)
  5. ^ G. Sitarski (1996). "On the Identity of the Periodic Comets 84P/Giclas and D/1931 R1". Acta Astronomica. 46 (1): 47–49. Bibcode:1996AcA....46...47S
  6. ^ H. L. Giclas & M. L. Kantz (1978-09-13). "Comet Giclas (1978k)". IAU Circular. 3264 (2). B. G. Marsden (ed.). Bibcode:1978IAUC.3264....2G
  7. ^ H. L. Giclas & M. L. Kantz (1978-09-14). "Comet Giclas (1978k)". IAU Circular. 3266 (1). B. G. Marsden (ed.). Bibcode:1978IAUC.3266....1G
  8. ^ C. Y. Shao (1978-09-18). "Periodic Comet Giclas (1978k)". IAU Circular. 3269 (2). B. G. Marsden (ed.). Bibcode:1978IAUC.3269....2S
  9. ^ G. W. Kronk & M. Meyer (2010). Cometography: A Catalog of Comets. Vol. 5: 1960–1982. Cambridge University Press. pp. 613–614. ISBN 978-0-521-87226-3.
  10. ^ "84P/Giclas – JPL Small-Body Database Lookup". ssd.jpl.nasa.gov. Jet Propulsion Laboratory. Retrieved 2012-02-18.