External links
- 100P/Hartley at the JPL Small-Body Database
- 100P/Hartley at Seiichi Yoshida's website
| Discovery [1] | |
|---|---|
| Discovered by | Malcolm Hartley |
| Discovery site | UK Schmidt Telescope |
| Discovery date | 13 June 1985 |
| Designations | |
| P/1985 L1 P/1991 E1 | |
| |
| Orbital characteristics [2] [3] | |
| 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° |
| 37.687° | |
| Argument of periapsis | 181.96° |
| Mean anomaly | 67.750° |
| Last perihelion | 10 August 2022 |
| Next perihelion | 15 December 2028 [4] |
| TJupiter | 2.851 |
| Earth MOID | 1.003 AU |
| Jupiter MOID | 0.133 AU |
| Physical characteristics [2] | |
Mean radius | < 1.2 km (0.75 mi) [5] |
| 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]
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]
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 on February 1988, passing within 0.36 AU (54 million km) from the giant planet. [10]
