For other comets of the same name, see Comet Hartley.
100P/Hartley
DiscovererMalcolm Hartley
Discovery siteUK Schmidt Telescope
Discovery date13 June 1985
Mpc nameP/1985 L1
P/1991 E1
Designations
  • Hartley 1
  • 1985 VII, 1991 VII
  • 1985f, 1991j
Epoch13 September 2023 (JD 2460200.5)
Observation arc37.17 years
Obs658
Perihelion2.018 AU
Aphelion4.844 AU
Semimajor3.416 AU
Eccentricity0.41183
Period6.354 years
Inclination25.567°
Asc node37.687°
Arg peri181.96°
Mean67.750°
Tjup2.851
Earth moid1.003 AU
Jupiter moid0.133 AU
Mean radius< 1.2 km (0.75 mi)[1]
M 110.0
M 216.2
Last p10 August 2022
Next p15 December 2028[2]

Comet Hartley 1, also known as 100P/Hartley, is a Jupiter family comet with a 6.35-year orbit around the Sun. It is one of 12 comets discovered by Australian astronomer, Malcolm Hartley.

On 29 April 2164, the comet will pass 0.487 astronomical units from Earth.[3]

Observational history

Discovery

Malcolm Hartley discovered the comet from CCD images taken from the UK Schmidt Telescope in Australia on 13 June 1985.[4] At the time, the comet was a 16th-magnitude object within the constellation Virgo,[a] with a prominent tail extending about 1 arcminute towards the southeast. Despite the discovery announcement, Hartley remained the comet's only observer for the next three weeks.[5]

Follow-up observations

An additional observation by Hartley on 10 July 1985 has allowed Brian G. Marsden to compute the elliptical orbit of the comet for the first time, revealing that it was a short-period comet with a 5.66-year orbit around the Sun.[6] James B. Gibson obtained the only known Northern hemisphere observations of the comet during its first apparition on 27–29 July 1985.[5] It was last detected by Alan C. Gilmore on 14 August 1985.[5]

The small number of observations during its 1985 apparition has caused uncertainties in revising its orbit that it was almost considered lost.[7] It was successfully recovered by David H. Levy, Carolyn and Eugene Shoemaker on the night of 12 March 1991,[8] about 16 degrees from its predicted position.[9] Marsden later noted that the comet made a close encounter with Jupiter on February 1988, passing within 0.36 astronomical units from the giant planet.[9]

References

Notes

  1. ^ Reported initial position upon discovery was: α = , δ = [5]

Citations

  1. ^ P. L. Lamy; I. Toth; Y. R. Fernández; H. A. Weaver (2004). "The Sizes, Shapes, Albedos, and Colors of Cometary Nuclei". Comets II. pp. 223–264. JSTOR j.ctv1v7zdq5.22
  2. ^ "Horizons Batch for 100P/Hartley 1 on 2028-Dec-15" (Perihelion occurs when rdot flips from negative to positive). JPL Horizons. Retrieved 2023-04-29. (JPL#38/Soln.date: 20 August 2022)
  3. ^ "100P/Hartley 1 – JPL Small-Body Database Lookup". ssd.jpl.nasa.gov. Jet Propulsion Laboratory. Retrieved 2025-05-22.
  4. ^ M. Hartley (1985-06-20). "Comet Hartley (1985f)". IAU Circular. 4077 (1). B. G. Marsden (ed.). Bibcode:1985IAUC.4077....1H
  5. ^ Kronk, Meyer & Seargent 2017, pp. 149–150.
  6. ^ M. Hartley (1985-07-18). "Periodic Comet Hartley (1985f)". IAU Circular. 4084 (1). B. G. Marsden (ed.). Bibcode:1985IAUC.4084....1H
  7. ^ G. W. Kronk. "100P/Hartley 1". Cometography.com. Retrieved 2025-05-22.
  8. ^ Kronk, Meyer & Seargent 2017, pp. 574–575.
  9. ^ C. S. Shoemaker; E. M. Shoemaker; D. H. Levy et al. (1991-03-16). "Periodic Comet Hartley (1991j)". IAU Circular. 5209 (1). D. W. Green (ed.). Bibcode:1991IAUC.5209....1S

Bibliography

  • Kronk, Gary W.; Meyer, Maik; Seargent, David A. J. (2017). Cometography: A Catalog of Comets. Vol. 6: 1983–1993. Cambridge University Press. ISBN 978-0-521-87216-4.