121P/Shoemaker–Holt

Not to be confused with 128P/Shoemaker–Holt. For other comets discovered by Carolyn and Eugene Shoemaker, see Comet Shoemaker.
121P/Shoemaker-Holt
Infrared image of Comet Shoemaker–Holt from the Spitzer Space Telescope on 1 August 2006
Discovery[1]
Discovered byCarolyn S. Shoemaker
Eugene Merle Shoemaker
Henry E. Holt
Discovery date9 March 1989
Designations
P/1989 E2, P/1995 Q3
  • Shoemaker–Holt 2[2]
  • 1988 XI, 1989j
Orbital characteristics[3][4]
Epoch21 November 2025 (JD 2461000.5)
Observation arc37.19 years
Earliest precovery date4 March 1989
Number of
observations		798
Aphelion5.448 AU
Perihelion3.733 AU
Semi-major axis4.591 AU
Eccentricity0.18669
Orbital period9.835 years
Inclination20.162°
94.104°
Argument of
periapsis		12.047°
Mean anomaly87.563°
Last perihelion28 June 2023
Next perihelion5 May 2033[5]
TJupiter2.858
Earth MOID2.620 AU
Jupiter MOID0.131 AU
Physical characteristics[3]
Mean radius
3.61 km (2.24 mi)[6]
~10 hours[7]
(V–R) = 0.53±0.03[8]
Comet total
magnitude (M1)		6.7
Comet nuclear
magnitude (M2)		12.6

121P/Shoemaker–Holt, also known as Shoemaker–Holt 2, is a Jupiter-family comet with an orbital period of about 10 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.[1] It was recovered by James V. Scotti on 29 August 1995 in images obtained as part of the Spacewatch survey.[9]

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.[8] 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.[7]

References

  1. 1 2 C. S. Shoemaker; E. M. Shoemaker; H. E. Holt (10 March 1989). D. W. Green (ed.). "Comet Shoemaker–Holt (1989j)". IAU Circular. 4755 (1).
  2. ↑ "Periodic Comet Names and Designations". Planetary Data System: Small Body Node. NASA. Retrieved 14 July 2026.
  3. 1 2 "121P/Shoemaker–Holt 2 – JPL Small-Body Database Lookup". ssd.jpl.nasa.gov. Jet Propulsion Laboratory. Retrieved 13 July 2026.
  4. ↑ "121P/Shoemaker–Holt Orbit". Minor Planet Center. Retrieved 16 April 2026.
  5. ↑ "Horizons Batch for 121P/Shoemaker-Holt 2 (90001019) on 2033-May-05" (Perihelion occurs when rdot flips from negative to positive). JPL Horizons. Retrieved 16 April 2026.
  6. ↑ M. M. Knight; R. Kokotanekova; N. H. Samarasinha (2024). "Physical and Surface Properties of Comet Nuclei from Remote Observations". In K. J. Meech (ed.). Comets III. University of Arizona Press. pp. 361–404. arXiv:2304.09309. JSTOR jj.21819446.18.
  7. 1 2 C. Snodgrass; S. C. Lowry; A. Fitzsimmons (2008). "Optical observations of 23 distant Jupiter Family Comets, including 36P/Whipple at multiple phase angles". Monthly Notices of the Royal Astronomical Society. 385 (2): 737–756. arXiv:0712.4204. Bibcode:2008MNRAS.385..737S. doi:10.1111/j.1365-2966.2008.12900.x.
  8. 1 2 Y. R. Fernández; M. S. P. Kelley; P. L. Lamy; I. Toth; O. Groussin; et al. (2013). "Thermal properties, sizes, and size distribution of Jupiter-family cometary nuclei". Icarus. 226 (1): 1138–1170. arXiv:1307.6191. Bibcode:2013Icar..226.1138F. doi:10.1016/j.icarus.2013.07.021.
  9. ↑ J. V. Scotti; D. W. Green; B. G. Marsden (1 September 1995). "Comet P/1995 Q3 (Shoemaker-Holt 2)". IAU Circular. 6219 (2). Bibcode:1995IAUC.6219....2S. ISSN 0081-0304.
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