322P/SOHO
Kracht sungrazer comet
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322P/SOHO is the first periodic comet to be discovered using the automated telescopes of the Solar and Heliospheric Observatory (SOHO) spacecraft, and second to be given a numbered designation, after 321P/SOHO.[8] At perihelion, it is six times closer to the Sun than the planet Mercury.
| Discovery | |
|---|---|
| Discovered by | SOHO |
| Discovery date | 4 September 1999 |
| Designations | |
| |
| SOHO-85[1] SOHO-661 | |
| Orbital characteristics[2][3] | |
| Epoch | 15 September 2015 (JD 2457280.5) |
| Observation arc | 15.93 years |
| Earliest precovery date | 27 November 254?[4] |
| 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)[5] |
| 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[5] |
| TJupiter | 2.347 |
| Earth MOID | 0.092 AU |
| Jupiter MOID | 1.044 AU |
| Physical characteristics[6][7] | |
| Dimensions | ~150–320 m (490–1,050 ft) |
Mean density | ~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 |
Observational history
The comet was first spotted by Terry Lovejoy after analyzing SOHO imagery on 4 September 1999.
After Kazimieras Černis spotted another SOHO comet in 2003, Sebastian F. Hönig, later determined that both P/1999 R1 and P/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 as P/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]
Possible connection with the Great Comet of 254 AD
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.[4][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]
Physical characteristics
322P/SOHO is either an extinct comet or an active asteroid.[14] Light-curve and infrared observations by Spitzer in 2016 suggest that its nucleus is probably only 150–320 m (490–1,050 ft) in diameter, with a rotation period lasting 2.8±0.3 hours.[7]
Orbit
| 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 the Kracht 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.[2][16]
Exploration
On 2 September 2019, NASA's Parker 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]