125P/Spacewatch is a Jupiter-family comet with a 5.53-year orbit around the Sun. It was discovered on 8 September 1991 by Tom Gehrels using the 0.91 m Spacewatch telescope at the Kitt Peak National Observatory.[6] It was the first comet discovered with the use of a CCD,[7] and also the faintest comet upon discovery up to that point.[6] Its nucleus has a diameter of 1.66 km (1.03 mi).[5]
 Comet 125P/Spacewatch photographed from the Zwicky Transient Facility on 3 June 2024 | |
| Discovery[1] | |
|---|---|
| Discovered by | Spacewatch Tom Gehrels |
| Discovery site | Kitt Peak Observatory |
| Discovery date | 8 September 1991 |
| Designations | |
| P/1991 R2, P/1996 F1 | |
| 1990 XXIX, 1991x | |
| Orbital characteristics[2][3] | |
| Epoch | 11 August 2015 (JD 2457245.5) |
| Observation arc | 33.12 years |
| Number of observations | 1,297 |
| Aphelion | 4.728 AU |
| Perihelion | 1.523 AU |
| Semi-major axis | 3.126 AU |
| Eccentricity | 0.51269 |
| Orbital period | 5.526 years |
| Inclination | 9.988° |
| 153.19° | |
| Argument of periapsis | 87.145° |
| Mean anomaly | 161.39° |
| Last perihelion | 7 March 2024 |
| Next perihelion | 15 September 2029[4] |
| TJupiter | 2.975 |
| Earth MOID | 0.554 AU |
| Jupiter MOID | 0.810 AU |
| Physical characteristics[2] | |
Mean radius | 0.83 km (0.52 mi)[5] |
| Comet total magnitude (M1) | 12.9 |
| Comet nuclear magnitude (M2) | 16.7 |
Observational history
editThe comet was discovered in images taken by the 0.91 m Spacewatch telescope at the Kitt Peak National Observatory by Tom Gehrels on September 8, 1991, as an essentially stellar object with an apparent magnitude of 21, with a tail more than 5 arcminutes long.[1] Brian G. Marsden calculated a parabolic and an elliptical orbit, with the elliptical orbit suggesting an orbital period of 5.58 years and a perihelion date on 18 December 1990.[8]
The comet was recovered on 21 March 1996 by the Spacewatch telescope from James V. Scotti and J. Montani, with an apparent magnitude of 17.6, a tail measuring 0.66 arcminutes long and a coma measuring 15 arcseconds across. The orbit calculated after the recovery indicates an orbital period of 5.56 years.[9] During that apparition the comet experienced an outburst in late July 1996 and brightened to a magnitude of 14.5.[6] During the 2002 apparition the comet brightened to a magnitude of 18.[6]
References
edit- 1 2 J. V. Scotti; T. Gehrels (10 September 1991). B. G. Marsden (ed.). "Comet Spacewatch (1991x)". IAU Circular. 5341 (1). Bibcode:1991IAUC.5341....1S. ISSN 0081-0304.
- 1 2 "125P/Spacewatch – JPL Small-Body Database Lookup". ssd.jpl.nasa.gov. Jet Propulsion Laboratory. Retrieved 2 June 2013.
- ↑ "125P/Spacewatch Orbit". Minor Planet Center. Retrieved 17 June 2014.
- ↑ "Horizons Batch for 125P/Spacewatch (90001031) on 2029-Sep-15" (Perihelion occurs when rdot flips from negative to positive). JPL Horizons. Retrieved 16 April 2026. (JPL#58 Soln.date: 2024-Oct-29)
- 1 2 G. Tancredi; J. A. Fernández; H. Rickman; J. Licandro (2006). "Nuclear magnitudes and the size distribution of Jupiter family comets". Icarus. 182 (2): 527–549. Bibcode:2006Icar..182..527T. doi:10.1016/j.icarus.2006.01.007.
- 1 2 3 4 G. W. Kronk. "125P/Spacewatch". Cometography.com. Retrieved 2 June 2013.
- ↑ "SPACEWATCH® News and History". spacewatch.lpl.arizona.edu. Retrieved 11 August 2024.
- ↑ J. V. Scotti; T. Gehrels (12 September 1991). B. G. Marsden (ed.). "Comet Spacewatch (1991x)". IAU Circular. 5343 (1). Bibcode:1991IAUC.5343....1S. ISSN 0081-0304.
- ↑ J. V. Scotti; J. Montani; S. Nakano (22 March 1996). B. G. Marsden (ed.). "Comet P/1996 F1 (Spacewatch)". IAU Circular. 6349 (1). Bibcode:1996IAUC.6349....1S. ISSN 0081-0304.
External links
edit- 125P/Spacewatch at the JPL Small-Body Database
- 125P/Spacewatch at Gary W. Kronk's Cometography
- 125P/Spacewatch at Seiichi Yoshida's website