322P/SOHO
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) on 21 August 2023 at around apparent magnitude 6 and only 3 degrees from the Sun. At perihelion it is six times closer to the Sun than the planet Mercury is at perihelion.
| Discovery | |
|---|---|
| Discovered by | T. Lovejoy K. Černis B. Zhou S. F. Hönig |
| Discovery date | September 4, 1999 |
| Designations | |
Alternative designations | P/1999 R1, P/2003 R5, P/2007 R5, P/2011 R4 |
| Orbital characteristics | |
| Epoch | 2019-08-25 (JD 2458720.5) |
| Observation arc | 15.9 years |
| Number of observations | 318 |
| Aphelion | 4.967 AU |
| Perihelion | 0.0507 AU (16% of Mercury's perihelion) |
| Semi-major axis | 2.509 AU |
| Eccentricity | 0.9798 |
| Orbital period | 3.97 yr |
| Max. orbital speed | 187 km/s (2023) |
| Min. orbital speed | 1.9 km/s (2017-Sep-01) |
| Inclination | 11.46° |
| Last perihelion | August 31, 2019 September 4, 2015 September 7, 2011 September 11, 2007 |
| Next perihelion | August 21, 2023 |
| TJupiter | 2.347 |
| Earth MOID | 0.092 AU (13,800,000 km) |
| Physical characteristics | |
| Dimensions | ~100-200 m |
| Comet total magnitude (M1) | 19.00 ± 0.09 |
| Perihelion distance at different epochs | |||||||
| 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 | ||||||
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.
As it passed to within 7.9 million kilometres of the Sun, around 0.05 AU, it brightened by a factor of around a million. This is common behavior for a comet.
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.
Discovery credit goes to Terry Lovejoy (Australia, 1999), Kazimieras Černis (Lithuania, 2003), and Bo Zhou (China, 2007).
The second periodic comet discovered by SOHO is P/2003 T12 (SOHO).
It was observed again in September 2019. On April 11, 1947 it passed about 7.1 ± 0.22 million km (4.4 ± 0.14 million mi) from Earth.