C/1985 R1 (Hartley–Good)
| Discovery[1] | |
|---|---|
| Discovered by | Malcolm Hartley A. R. Good |
| Discovery site | Siding Spring Observatory |
| Discovery date | 11 September 1985 |
| Designations | |
| 1985 XVII, 1985l[2] | |
| Orbital characteristics[3] | |
| Epoch | 2 November 1985 (JD 2446371.5) |
| Observation arc | 187 days |
| Earliest precovery date | 21 August 1985 |
| Number of observations | 165 |
| Aphelion | ~12,300 AU |
| Perihelion | 0.695 AU |
| Semi-major axis | ~6,160 AU |
| Eccentricity | 0.99989 |
| Orbital period | ~480,000 years |
| Inclination | 79.929° |
| 358.39° | |
| Argument of periapsis | 87.033° |
| Mean anomaly | 359.99° |
| Last perihelion | 9 December 1985 |
| TJupiter | 0.182 |
| Earth MOID | 0.221 AU |
| Jupiter MOID | 2.966 AU |
| Physical characteristics[5][6] | |
Mean radius | 0.88±0.05 km |
| Mass | 1.10×1012 kg |
Mean density | 490±70 kg/m3 |
| Comet total magnitude (M1) | 8.3 |
| 6.3–6.6 (1985 apparition)[4] | |
Comet Hartley–Good, formally designated as C/1985 R1, is a non-periodic comet that was observed from September 1985 to March 1986.[4] It is the sixth comet discovered overall by Malcolm Hartley and the only one for A. R. Good.[1]
Physical characteristics
Ground observations from the comet reveal the presence of organic molecules like CN, CH, C
2 and C
3 within its coma.[7][8] In comparison to comets like 21P/Giacobini–Zinner, the dust-to-gas production ratio for Hartley–Good is relatively low, noting that its dust production is inversely proportional to its distance from the Sun.[9]
Narrow-band photometry measurements reveal that the nucleus of Hartley–Good has an effective radius of roughly 1.7 km (1.1 mi),[10] however this was later revised to 0.88±0.05 km.[5][6] Recorded light-curve data from the comet suggests that water ice from its surface had started to sublimate at a distance of 2.8 AU (420 million km) from the Sun, while also remaining active throughout its most recent apparition.[11]
References
- ^ a b M. Hartley; A. R. Good (13 September 1985). B. G. Marsden (ed.). "Comet Hartley–Good (1985l)". IAU Circular. 4107 (1).
- ^ "Comet Names and Designations". International Comet Quarterly. Retrieved 26 June 2025.
- ^ "C/1985 R1 (Hartley–Good) – JPL Small-Body Database Lookup". ssd.jpl.nasa.gov. Jet Propulsion Laboratory. Retrieved 26 June 2025.
- ^ a b G. W. Kronk; M. Meyer; D. A. J. Seargent (2017). Cometography: A Catalog of Comets. Vol. 6: 1983–1993. Cambridge University Press. pp. 160–165. ISBN 978-0-521-87216-4.
- ^ a b M. L. Paradowski (2022). "A New Indirect Method of Determining Density of Cometary Nuclei" (PDF). Acta Astronomica. 72 (2): 141–159. Bibcode:2022AcA....72..141P. doi:10.32023/0001-5237/72.2.4. ISSN 0001-5237.
- ^ a b A. Sosa; J. A. Fernández (2011). "Masses of long-period comets derived from non-gravitational effects". Monthly Notices of the Royal Astronomical Society. 416 (1): 767–782. Bibcode:2011MNRAS.416..767S. doi:10.1111/j.1365-2966.2011.19111.x.
- ^ B. S. Rautela; P. S. Goraya; B. B. Sanwal; S. K. Gupta (1989). "Spectrophotometry of comet Hartley–Good (1985l)" (PDF). Earth, Moon, and Planets. 44 (3): 233–242. Bibcode:1989EM&P...44..233R. doi:10.1007/BF00054239.
- ^ P. D. Singh; W. F. Huebner; R. D. D. Costa; S. J. C. Landaberry; J. A. de Freitas Pacheco (1997). "Gas and dust release rates and color of dust in comets P/Halley (1986 III), P/Giacobini–Zinner (1985 XIII), and P/Hartley–Good (1985 XVII)". Planetary and Space Science. 45 (4): 455–467. Bibcode:1997P&SS...45..455S. doi:10.1016/S0032-0633(96)00123-7.
- ^ S. J. C. Landaberry; P. D. Singh; J. A. de Freitas Pacheco (1991). "Ground-based observations of Comets Giacobini–Zinner (1984e) and Hartley–Good (1985l)". Astronomy & Astrophysics. 246 (2): 597–602. Bibcode:1991A&A...246..597L. ISSN 0004-6361.
- ^ K. I. Churyumov; V. K. Rosenbush (1991). "Peculiarities of gas and dust production rates in comets P/Halley (1986 III), P/Giacobini–Zinner (1985 XIII), P/Hartley–Good (1985 XVII) and P/Thiele (1985 XIX)". Astronomische Nachrichten. 312 (6): 385–391. Bibcode:1991AN....312..385C. doi:10.1002/asna.2113120610. ISSN 0004-6337.
- ^ P. S. Goraya (1988). "Update on Comet Hartley–Good's light curve" (PDF). Earth, Moon, and Planets. 41 (3): 253–255. Bibcode:1988EM&P...41..253G. doi:10.1007/BF00113987.
External links
- C/1985 R1 at the JPL Small-Body Database
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