121P/Shoemaker–Holt
| Discovery | |
|---|---|
| Discovered by | Carolyn S. Shoemaker Eugene Merle Shoemaker Henry E. Holt |
| Discovery date | March 9, 1989 |
| Designations | |
| 1989j; 1988 XI; 1995 Q3 | |
| Orbital characteristics | |
| Epoch | March 6, 2006 |
| Aphelion | 5.376 AU |
| Perihelion | 2.65 AU |
| Semi-major axis | 4.013 AU |
| Eccentricity | 0.3396 |
| Orbital period | 8.039 a |
| Inclination | 17.7218° |
| Last perihelion | September 8, 2013 September 1, 2004 |
| Next perihelion | 2023-Jun-28 |
| Physical characteristics | |
Mean radius | 3.61 km (2.24 mi) |
| ~10 hours | |
| (V–R) = 0.53±0.03 | |
121P/Shoemaker–Holt, also known as Shoemaker-Holt 2, is a periodic comet in the Solar System with an orbital period of about 8 years. The comet was discovered by Carolyn S. Shoemaker, Eugene M. Shoemaker, and Henry E. Holt on 9 March 1989. The comet then had an apparent magnitude of 13, was diffuse and had a tail about 2 arcminutes long. It was recovered by James V. Scotti on 29 August 1995 in images obtained as part of the Spacewatch survey.
The nucleus of the comet is estimated to have a radius of 3.87 km based on infrared imaging by the Spitzer Space Telescope, when the comet displayed dust emission. Observations of the comet from the Isaac Newton Telescope indicate an effective radius of 3.61 kilometers. The rotational period was calculated to be 10 hours, but with high uncertainty.