|Discovered by||T. Lovejoy|
S. F. Hönig
|Discovery date||September 4, 1999|
|P/1999 R1, P/2003 R5, P/2007 R5, P/2011 R4|
|Orbital characteristics A|
|Epoch||January 1, 2013 (JD 2456293.5)|
|Observation arc||16 years|
|Semi-major axis||2.5158179 AU|
|Orbital period||3.99 yr|
|Max. orbital speed||186 km/s (2019)|
|Min. orbital speed||1.9 km/s (2017-Sep-01)|
|Earth MOID||0.092 AU (13,800,000 km)|
|19.00 ± 0.09|
|Last perihelion||August 31, 2019|
September 4, 2015
September 7, 2011
September 11, 2007
Comet 322P/SOHO, also designated P/1999 R1, P/2003 R5, P/2007 R5, and P/2011 R4, is the first periodic comet to be discovered using the automated telescopes of the SOHO (SOlar and Heliospheric Observatory) spacecraft, and second to be given a numbered designation, after 321P/SOHO. JPL Horizons next predicts 322P to come to perihelion (closest approach to the Sun) at 2019-Aug-31 12:25 UT.
The periodicity of this comet was predicted by Sebastian Hönig, a German graduate student and prolific asteroid discoverer, in 2006. The announcement of the new periodic comet was made after the predicted return was confirmed by SOHO and observer Bo Zhou on 10 September 2007. Out of approximately 1,350 SOHO-observed sungrazer comets, this is the first to be verified as a short-period comet; most sungrazers are long-period comets on near-parabolic orbits that do not repeat for thousands of years, if at all.
P/2007 R5 is probably an extinct comet. Extinct comets are those that have expelled most of their volatile ice and have little left to form a tail or coma. They are theorized to be common objects amongst the celestial bodies orbiting close to the Sun. P/2007 R5 (SOHO) is probably only 100–200 meters in diameter.
It was expected to return in September 2011, and was recovered by B. Zhou on September 6, 2011. It has a 2.8 hour light curve period suggesting its rotation. It is uncertain whether to classify it as a dead comet or asteroid.
It was observed again in September 2019.
- "322P/SOHO Orbit". Minor Planet Center. Retrieved April 10, 2017.
- Jaggard, Victoria (September 25, 2007). "Photo in the News: Sun Probe Spies New Periodic Comet". National Geographic News. National Geographic Society. Retrieved September 25, 2007.
- Marsden, Brian (September 18, 2007), "MPEC 2007-S16 : COMET P/1999 R1 = 2003 R5 = 2007 R5 (SOHO)", Minor Planet Electronic Circular (2007-S16)
- "SOHO's new catch: its first officially periodic comet". European Space Agency. September 25, 2007. Retrieved November 19, 2007.
- Rainer Kracht (September 7, 2011). "Recent comet discoveries 2123-2137". Yahoo Groups: SOHO Hunter. Retrieved September 11, 2011.
- Karl Battams (January 30, 2012). "The tale of a very shy comet..." Sungrazing Comets @ Navy.mil. Retrieved January 30, 2012.
- The case of the Sun-diving asteroid that thinks it's a comet Phil Plait, September 4, 2019