96P/Machholz
Comet 96P/Machholz or 96P/Machholz 1 is a short-period sungrazing comet discovered on May 12, 1986, by amateur astronomer Donald Machholz on Loma Prieta peak, in central California using 130 millimetres (5.1 in) binoculars. On June 6, 1986, 96P/Machholz passed 0.404 AU (60,400,000 km; 37,600,000 mi) from the Earth. 96P/Machholz last came to perihelion on January 31, 2023. The comet has an estimated diameter of around 6.4 km (4.0 mi).
96P/Machholz as seen by STEREO-A in April 2007 | |
| Discovery | |
|---|---|
| Discovered by | Donald Machholz |
| Discovery date | May 12, 1986 |
| Designations | |
Alternative designations | 96P, Machholz, Machholz 1, 1986 J2, 1991 XII, 1986e, 1986 VII |
| Orbital characteristics | |
| Epoch | 2028-May-29 (JD 2461920.5) |
| Aphelion | 5.944 AU |
| Perihelion | 0.1160 AU (38% of Mercury's perihelion) |
| Semi-major axis | 3.030 AU |
| Eccentricity | 0.9617 |
| Orbital period | 5.27 yr |
| Max. orbital speed | 122 km/s (440,000 km/h) |
| Inclination | 57.49° |
| Last perihelion | January 31, 2023, 02:02 UTC October 27, 2017, 23:03 UTC |
| Next perihelion | ≈May 12, 2028 |
96P/Machholz is unusual among comets in several respects. Other than small SOHO comets, its highly eccentric 5.29 year orbit has the smallest perihelion distance known among numbered/regular short-period comets, bringing it considerably closer to the Sun than the orbit of Mercury. It is also the only known short-period comet with both high orbital inclination and high eccentricity. In 2007, 96P/Machholz was found to be both carbon-depleted and cyanogen-depleted, a chemical composition nearly unique among comets with known compositions. The chemical composition implies a different and possible extrasolar origin.