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10P/Tempel
	Comet Tempel 2 in 1946 from Lick Observatory
Discovery
Discovered by	Ernst Wilhelm Leberecht Tempel
Discovery date	July 4, 1873
Designations
Alternative designations	1873 II; 1878 III; 1894 III;; 1899 IV; 1904 III; 1915 I;; 1920 II; 1925 IV; 1930 VII;; 1946 III; 1951 VIII; 1957 II;; 1962 VI; 1967 X; 1972 X;; 1978 V; 1983 X; 1988 XIV;; 1994 VII;
Orbital characteristics
Epoch	2026-07-19; (JD 2461240.5)
Aphelion	4.71 AU
Perihelion	1.418 AU
Semi-major axis	3.065 AU
Eccentricity	0.5374
Orbital period	5.37 yr
Inclination	12.03°
Longitude of; ascending node	117.8°
Argument of; periapsis	195.5°
Last perihelion	24 March 2021; 14 November 2015; 4 July 2010
Next perihelion	2026-Aug-02
Earth MOID	0.41 AU (61 million km)
Physical characteristics
Dimensions	10.6 km

10P/Tempel, also known as Tempel 2, is a periodic Jupiter-family comet with a 5-year orbital period. It was discovered on July 4, 1873 by Wilhelm Tempel.^[7] At the perihelion passage on 2 August 2026 the solar elongation is calculated at 164 degrees, with apparent magnitude approximately 8,^[4] with closest approach to Earth on 3 August 2026 at a distance of 0.414 AU (61.9 million km).^[1]

10P/Tempel closest Earth approach on 2026-Aug-03^[1]
Date & time of closest approach	Earth distance (AU)	Sun distance (AU)	Velocity wrt Earth (km/s)	Velocity wrt Sun (km/s)	Uncertainty region (3-sigma)	Reference
2026-Aug-03 20:59 ± 1 min	0.414 AU (61.9 million km; 38.5 million mi; 161 LD)	1.42 AU (212 million km; 132 million mi)	6.5	31.0	± 204 km	Horizons

The comet nucleus is estimated to be roughly the size of Halley's Comet at 10.6 kilometers in diameter with a low albedo of 0.022.^[1] The nucleus is dark because hydrocarbons on the surface have been converted to a dark, tar like substance by solar ultraviolet radiation. The nucleus is large enough that even near aphelion (furthest distance from the Sun which is near the orbit of Jupiter) the comet remains brighter than about magnitude 21.

During the 2010 apparition the comet brightened to about apparent magnitude 8.^[4] The most favorable apparition of 10P/Tempel 2 was in 1925 when it came within 0.35 AU (52 million km; 33 million mi) of Earth with an apparent magnitude of 6.5.^[7]

Proposed exploration

The Jet Propulsion Laboratory proposed a flyby of the comet with a flight spare of Mariner 4.^[8] The probe was instead used for a Venus flyby as Mariner 5.^[8]

References

^ ^a ^b ^c ^d ^e "JPL Small-Body Database Browser: 10P/Tempel 2" (last observation: 2014-03-29; arc: 67.91 years). Jet Propulsion Laboratory. Retrieved 2010-02-24.
^ ^a ^b ^c ^d "10P/Tempel Orbit". Minor Planet Center. Retrieved 2023-08-06.
^ 10P at Kazuo Kinoshita home page
^ ^a ^b ^c Seiichi Yoshida (2008-01-27). "10P/Tempel 2". Seiichi Yoshida's Comet Catalog. Retrieved 2010-02-24.
^ Syuichi Nakano (2007-04-10). "10P/Tempel 2 (NK 1460)". OAA Computing and Minor Planet Sections. Retrieved 2010-02-24.
^ "Horizons Batch for 10P/Tempel 2 (90000213) on 2026-Aug-02" (Perihelion occurs when rdot flips from negative to positive). JPL Horizons. Retrieved 2022-06-27. (JPL#K214/33 Soln.date: 2022-May-02)
^ ^a ^b Kronk, Gary W. "10P/Tempel 2". Archived from the original on 22 February 2010. Retrieved 2010-02-24. (Cometography Home Page)
^ ^a ^b Ulivi, Paolo; Harland, David M (2007). Robotic Exploration of the Solar System Part I: The Golden Age 1957-1982. Springer. pp. 57–58. ISBN 9780387493268.