| Discovery | |
|---|---|
| Discovered by | SOHO |
| Discovery date | 4 September 1999 |
| Designations | |
| |
| SOHO-85[1] SOHO-661 | |
| Orbital characteristics[4][5] | |
| Epoch | 15 September 2015 (JD 2457280.5) |
| Observation arc | 15.93 years |
| Earliestprecovery date | 27 November 254?[2] |
| Number of observations | 319 |
| Aphelion | 4.979 AU |
| Perihelion | 0.0507 AU |
| Semi-major axis | 2.516 AU |
| Eccentricity | 0.97869 |
| Orbital period | 3.992 years |
| Max.orbital speed | 187 km/s (2023)[3] |
| Min.orbital speed | 1.9 km/s (2017) |
| Inclination | 12.583° |
| 359.48° | |
| Argument of periapsis | 49.098° |
| Mean anomaly | 2.700° |
| Last perihelion | 21 August 2023[3] |
| TJupiter | 2.347 |
| EarthMOID | 0.092 AU |
| JupiterMOID | 1.044 AU |
| Physical characteristics[6][7] | |
| Dimensions | ~150–320 m (490–1,050 ft) |
Meandensity | ~1.00 g/cm3 |
| 2.8±0.3 hours | |
| 0.09–0.42 | |
| (V–R) =0.41±0.04 (R–I) =0.24±0.09 | |
| Comet total magnitude (M1) | 19.0 |
322P/SOHO is the firstperiodic comet to be discovered using the automated telescopes of theSolar and Heliospheric Observatory (SOHO) spacecraft, and second to be given a numbered designation, after321P/SOHO.[8] At perihelion, it is six times closer to the Sun than the planetMercury.
The comet was first spotted byTerry Lovejoy after analyzing SOHO imagery on 4 September 1999.
AfterKazimieras Černis spotted another SOHO comet in 2003,Sebastian F. Hönig, later determined that bothP/1999 R1 andP/2003 R5 might be the same object, where he predicted its return in 2007.[9][10] His calculations were later proven correct when it was successfully recovered by Bo Zhou asP/2007 R5 after analyzing SOHO images on 10 September 2007.[11] It became one of the first comets that SOHO has discovered that is confirmed to be periodic.
Bo Zhou recovered the comet once again on September 6, 2011.[6] It was observed again in September 2019.[12]
It has been suggested that 322P/SOHO is associated with a comet observed in November–December 254 AD and is mentioned in East Asian sources to have an extremely long tail.[2][13] If the association is correct, it is possible that the comet split in 254 AD, resulting in intense cometary activity, but activity decreased afterwards as the comet lost most of its volatiles, and no longer displays a tail or a prominent coma. Current activity is fueled by sodium sublimation.[13]
322P/SOHO is either anextinct comet or anactive asteroid.[14] Light-curve and infrared observations bySpitzer in 2016 suggest that itsnucleus is probably only 150–320 m (490–1,050 ft) in diameter, with a rotation period lasting2.8±0.3 hours.[7]
| Perihelion distance at different epochs[15] | |||||||
| Perihelion date | Perihelion (AU) | ||||||
|---|---|---|---|---|---|---|---|
| 1955-04-18 | 0.0651 | ||||||
| 1983-08-08 | 0.0597 | ||||||
| 1999-09-05 | 0.0563 | ||||||
| 2015-09-04 | 0.0535 | ||||||
| 2019-08-31 | 0.0506 | ||||||
| 2023-08-21 | 0.0501 | ||||||
| 2027-08-11 | 0.0505 | ||||||
| 2031-08-01 | 0.0479 | ||||||
| 2047-05-23 | 0.0451 | ||||||
322P/SOHO is a member of theKracht sungrazer family of comets.[1] On April 11, 1947 it passed about 7.1 ± 0.22 million km (4.4 ± 0.14 million mi) from Earth.[4][16]
On 2 September 2019, NASA'sParker Solar Probe incidentally passed the tail of 322P/SOHO at a distance of 0.012 AU (1.8 million km), making direct measurements of the comet as it interacts with the solar wind.[17]
| Numbered comets | ||
|---|---|---|
| Previous 321P/SOHO | 322P/SOHO | Next 323P/SOHO |
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