100P/Hartley

100P/Hartley
Discovery
Discovered by	Malcolm Hartley
Discovery site	UK Schmidt Telescope
Discovery date	13 June 1985
Designations
MPC designation	P/1985 L1; P/1991 E1
Alternative designations	Hartley 1; 1985 VII, 1991 VII; 1985f, 1991j;
Orbital characteristics
Epoch	13 September 2023 (JD 2460200.5)
Observation arc	37.17 years
Number of; observations	658
Aphelion	4.844 AU
Perihelion	2.018 AU
Semi-major axis	3.416 AU
Eccentricity	0.41183
Orbital period	6.354 years
Inclination	25.567°
Longitude of; ascending node	37.687°
Argument of; periapsis	181.96°
Mean anomaly	67.750°
Last perihelion	10 August 2022
Next perihelion	15 December 2028
TJupiter	2.851
Earth MOID	1.003 AU
Jupiter MOID	0.133 AU
Physical characteristics
Mean radius	< 1.2 km (0.75 mi)
Comet total; magnitude (M1)	10.0
Comet nuclear; magnitude (M2)	16.2

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 AU (72.9 million km; 45.3 million mi) from Earth.^[2]

Observational history

Discovery

Malcolm Hartley discovered the comet from CCD images taken from the UK Schmidt Telescope in Australia on 13 June 1985.^[1] 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.^[6]

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.^[7] James B. Gibson obtained the only known Northern hemisphere observations of the comet during its first apparition on 27–29 July 1985.^[6] It was last detected by Alan C. Gilmore on 14 August 1985.^[6]

The small number of observations during its 1985 apparition has caused uncertainties in revising its orbit that it was almost considered lost.^[8] It was successfully recovered by David H. Levy, Carolyn and Eugene Shoemaker on the night of 12 March 1991,^[9] about 16 degrees from its predicted position.^[10] Marsden later noted that the comet made a close encounter with Jupiter in February 1988, passing within 0.36 AU (54 million km) from the giant planet.^[10]

References

Notes

↑ Reported initial position upon discovery was: α = 11^h 48^m , δ = 4° 21′^[6]

Citations

1 2 M. Hartley (20 June 1985). B. G. Marsden (ed.). "Comet Hartley (1985f)". IAU Circular. 4077 (1). Bibcode:1985IAUC.4077....1H.
1 2 3 "100P/Hartley 1 – JPL Small-Body Database Lookup". ssd.jpl.nasa.gov. Jet Propulsion Laboratory. Retrieved 22 May 2025.
↑ "100P/Hartley Orbit". Minor Planet Center. Retrieved 1 November 2014.
↑ "Horizons Batch for 100P/Hartley 1 on 2028-Dec-15" (Perihelion occurs when rdot flips from negative to positive). JPL Horizons. Retrieved 29 April 2023. (JPL#38/Soln.date: 20 August 2022)
↑ 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. JSTOR j.ctv1v7zdq5.22. Archived from the original (PDF) on 9 October 2022. Retrieved 23 May 2025.
1 2 3 4 Kronk, Meyer & Seargent 2017, pp. 149–150.
↑ M. Hartley (18 July 1985). B. G. Marsden (ed.). "Periodic Comet Hartley (1985f)". IAU Circular. 4084 (1). Bibcode:1985IAUC.4084....1H.
↑ G. W. Kronk. "100P/Hartley 1". Cometography.com. Retrieved 22 May 2025.
↑ Kronk, Meyer & Seargent 2017, pp. 574–575.
1 2 C. S. Shoemaker; E. M. Shoemaker; D. H. Levy; et al. (16 March 1991). D. W. Green (ed.). "Periodic Comet Hartley (1991j)". IAU Circular. 5209 (1). 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.

External links

100P/Hartley at the JPL Small-Body Database
- Close approach · Discovery · Ephemeris · Orbit viewer · Orbit parameters · Physical parameters
100P/Hartley at Seiichi Yoshida's website

Numbered comets

Previous
99P/Kowal

100P/Hartley

Next
101P/Chernykh

[7] Reported initial position upon discovery was: α = 11^h 48^m , δ = 4° 21′^[6]

[IAUC_4077-1] 1 2 M. Hartley (20 June 1985). B. G. Marsden (ed.). "Comet Hartley (1985f)". IAU Circular. 4077 (1). Bibcode:1985IAUC.4077....1H.

[jpldata-2] 1 2 3 "100P/Hartley 1 – JPL Small-Body Database Lookup". ssd.jpl.nasa.gov. Jet Propulsion Laboratory. Retrieved 22 May 2025.

[MPC-3] "100P/Hartley Orbit". Minor Planet Center. Retrieved 1 November 2014.

[Horizons2028-4] "Horizons Batch for 100P/Hartley 1 on 2028-Dec-15" (Perihelion occurs when rdot flips from negative to positive). JPL Horizons. Retrieved 29 April 2023. (JPL#38/Soln.date: 20 August 2022)

[Lamy_2004-5] 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. JSTOR j.ctv1v7zdq5.22. Archived from the original (PDF) on 9 October 2022. Retrieved 23 May 2025.

[FOOTNOTEKronkMeyerSeargent2017149–150-6] 1 2 3 4 Kronk, Meyer & Seargent 2017, pp. 149–150.

[IAUC_4084-8] M. Hartley (18 July 1985). B. G. Marsden (ed.). "Periodic Comet Hartley (1985f)". IAU Circular. 4084 (1). Bibcode:1985IAUC.4084....1H.

[cometography-9] G. W. Kronk. "100P/Hartley 1". Cometography.com. Retrieved 22 May 2025.

[FOOTNOTEKronkMeyerSeargent2017574–575-10] Kronk, Meyer & Seargent 2017, pp. 574–575.

[IAUC_5209-11] 1 2 C. S. Shoemaker; E. M. Shoemaker; D. H. Levy; et al. (16 March 1991). D. W. Green (ed.). "Periodic Comet Hartley (1991j)". IAU Circular. 5209 (1). Bibcode:1991IAUC.5209....1S.

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