120P/Mueller

120P/Mueller
Discovery
Discovered by	Jean E. Mueller
Discovery site	Palomar Observatory
Discovery date	18 October 1987
Designations
MPC designation	P/1987 U2; P/1995 O2
Alternative designations	Mueller 1; 1987 XXXI, 1987a1
Orbital characteristics
Epoch	6 September 2007 (JD 2454349.5)
Observation arc	34.14 years
Number of; observations	147
Aphelion	5.527 AU
Perihelion	2.744 AU
Semi-major axis	4.136 AU
Eccentricity	0.33654
Orbital period	8.412 years
Inclination	8.791°
Longitude of; ascending node	4.443°
Argument of; periapsis	30.008°
Mean anomaly	125.57°
Last perihelion	7 May 2021
Next perihelion	5 April 2029
TJupiter	2.917
Earth MOID	1.754 AU
Jupiter MOID	0.265 AU
Physical characteristics
Mean radius	0.77 km (0.48 mi)
Comet total; magnitude (M1)	6.6
Comet nuclear; magnitude (M2)	16.4

120P/Mueller, also known as Mueller 1, is a Jupiter-family comet with an 8.4-year orbit around the Sun. It is one of 15 comets discovered by American astronomer, Jean Mueller.

Observational history

Jean Mueller first spotted the comet on photographic plates exposed from the Palomar Observatory on the night of 18 October 1987.^[1] She described the new comet as a diffuse 17th-magnitude object within the constellation Pisces.^[a] A condensation and an apparent tail about 20–30 arcseconds in length towards the south-southwest was also noted.^[6] Orbital calculations using follow-up observations until 27 October 1987 helped Daniel W. E. Green to determine Mueller's comet as periodic, at the time having an orbital period of roughly 8.21 years.^[7]

James V. Scotti recovered the comet from the Kitt Peak Observatory on 30 July 1995 as P/1995 O1.^[8] It was a 22nd-magnitude object at the time of its recovery.^[8] The comet was observed from every subsequent apparition since. It most recently came to perihelion in May 2021^[3] and underwent a 1.4 magnitude outburst in August 2021.^[9]

Physical characteristics

Initial estimates of the size of its nucleus in 2004 was approximately 3.0 km (1.9 mi) in diameter.^[10] Optical photometry obtained in 2007 revised this to half of the previous estimate, currently about 1.54 km (0.96 mi) in diameter.^[5]

Notes

↑ Reported initial position upon discovery was: α = 1^h 12^m 47.4^s, δ = 12° 25′ 50″^[6]

References

1 2 J. E. Mueller; N. Reid; A. Maury (19 October 1987). D. W. Green (ed.). "Comet Mueller (1987a1)". IAU Circular. 4472 (2). Bibcode:1987IAUC.4472....2M.
1 2 "120P/Mueller 1 – JPL Small-Body Database Lookup". ssd.jpl.nasa.gov. Jet Propulsion Laboratory. Retrieved 5 December 2025.
1 2 "120P/Mueller Orbit". Minor Planet Center. Retrieved 17 June 2014.
↑ "Horizons Batch for 120P/Mueller 1 on 2029-Apr-05" (Perihelion occurs when rdot flips from negative to positive). JPL Horizons. Retrieved 13 September 2021. (JPL#20/Soln.date: 2021-Apr-15)
1 2 C. S. Snodgrass; S. C. Lowry; A. Fitzsimmons (2007). "Optical observations of 23 distant Jupiter Family Comets, including 36P/Whipple at multiple phase angles" (PDF). 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. S2CID 55536237.
1 2 G. W. Kronk; M. Meyer; D. A. J. Seargent (2017). Cometography: A Catalog of Comets. Vol. 6: 1983–1994. Cambridge: Cambridge University Press. pp. 320–322. ISBN 978-0-521-87216-4.
↑ E. M. Shoemaker; C. S. Shoemaker; H. Holt; et al. (27 October 1987). D. W. Green (ed.). "Periodic Comet Mueller (1987a1)". IAU Circular. 4480 (1). Bibcode:1987IAUC.4480....1S.
1 2 J. V. Scotti; S. Nakano (3 August 1995). B. G. Marsden (ed.). "Comet P/1995 O1 (Mueller)". IAU Circular. 6199 (1). Bibcode:1995IAUC.6199....1S.
↑ M. S. P. Kelley. "Small Apparent Outburst of Comet 120P/Mueller 1". The Astronomer's Telegram. 14876: 1. Bibcode:2021ATel14876....1K.
↑ P. L. Lamy; I. Toth; Y. R. Fernández; H. A. Weaver (2004). "The Sizes, Shapes, Albedos, and Colors of Cometary Nuclei" (PDF). Comets II. University of Arizona Press. pp. 223–264. Bibcode:2004come.book..223L. doi:10.2307/j.ctv1v7zdq5.22. ISBN 978-0-8165-2450-1. JSTOR j.ctv1v7zdq5.22. Archived from the original (PDF) on 9 October 2022. Retrieved 5 December 2025.

External links

120P/Mueller at the JPL Small-Body Database
- Close approach · Discovery · Ephemeris · Orbit viewer · Orbit parameters · Physical parameters
120P/Mueller at Seiichi Yoshida's website
120P/Mueller at Gary W. Kronk's Cometography

Numbered comets

Previous
119P/Parker–Hartley

120P/Mueller

Next
121P/Shoemaker–Holt

[7] Reported initial position upon discovery was: α = 1^h 12^m 47.4^s, δ = 12° 25′ 50″^[6]

[IAUC_4472-1] 1 2 J. E. Mueller; N. Reid; A. Maury (19 October 1987). D. W. Green (ed.). "Comet Mueller (1987a1)". IAU Circular. 4472 (2). Bibcode:1987IAUC.4472....2M.

[jpldata-2] 1 2 "120P/Mueller 1 – JPL Small-Body Database Lookup". ssd.jpl.nasa.gov. Jet Propulsion Laboratory. Retrieved 5 December 2025.

[MPC-3] 1 2 "120P/Mueller Orbit". Minor Planet Center. Retrieved 17 June 2014.

[Horizons2029-4] "Horizons Batch for 120P/Mueller 1 on 2029-Apr-05" (Perihelion occurs when rdot flips from negative to positive). JPL Horizons. Retrieved 13 September 2021. (JPL#20/Soln.date: 2021-Apr-15)

[Snodgrass_2007-5] 1 2 C. S. Snodgrass; S. C. Lowry; A. Fitzsimmons (2007). "Optical observations of 23 distant Jupiter Family Comets, including 36P/Whipple at multiple phase angles" (PDF). 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. S2CID 55536237.

[Kronk_2017-6] 1 2 G. W. Kronk; M. Meyer; D. A. J. Seargent (2017). Cometography: A Catalog of Comets. Vol. 6: 1983–1994. Cambridge: Cambridge University Press. pp. 320–322. ISBN 978-0-521-87216-4.

[IAUC_4480-8] E. M. Shoemaker; C. S. Shoemaker; H. Holt; et al. (27 October 1987). D. W. Green (ed.). "Periodic Comet Mueller (1987a1)". IAU Circular. 4480 (1). Bibcode:1987IAUC.4480....1S.

[IAUC_6199-9] 1 2 J. V. Scotti; S. Nakano (3 August 1995). B. G. Marsden (ed.). "Comet P/1995 O1 (Mueller)". IAU Circular. 6199 (1). Bibcode:1995IAUC.6199....1S.

[Kelley_2021-10] M. S. P. Kelley. "Small Apparent Outburst of Comet 120P/Mueller 1". The Astronomer's Telegram. 14876: 1. Bibcode:2021ATel14876....1K.

[Lamy_2004-11] P. L. Lamy; I. Toth; Y. R. Fernández; H. A. Weaver (2004). "The Sizes, Shapes, Albedos, and Colors of Cometary Nuclei" (PDF). Comets II. University of Arizona Press. pp. 223–264. Bibcode:2004come.book..223L. doi:10.2307/j.ctv1v7zdq5.22. ISBN 978-0-8165-2450-1. JSTOR j.ctv1v7zdq5.22. Archived from the original (PDF) on 9 October 2022. Retrieved 5 December 2025.

[1]

[2]

[3]

[4]

[5]

[a]

[6]

[7]

[8]

[9]

[10]