Lexell's Comet
D/1770 L1, popularly known as Lexell's Comet after its orbit computer Anders Johan Lexell, was a comet discovered by astronomer Charles Messier in June 1770. It is notable for having passed closer to Earth than any other comet in recorded history, approaching to a distance of only 0.015 astronomical units (2,200,000 km; 1,400,000 mi), or six times the distance from the Earth to the Moon. The comet has not been seen since 1770 and is considered a lost comet.
| Discovery | |
|---|---|
| Discovered by | Charles Messier |
| Discovery date | June 14, 1770 |
| Designations | |
| 1770 I, P/Lexell, Lexell's Comet | |
| Orbital characteristics | |
| Epoch | 1770-Aug-14 (JD 2367764.5) |
| Aphelion | 5.6184 ± 0.0409 AU |
| Perihelion | 0.6746 ± 0.003 AU (before Jupiter encounter of 1779) |
| Semi-major axis | 3.1465 ± 0.0206 AU |
| Eccentricity | 0.7856 ± 0.0013 |
| Orbital period | 5.58 years (2039 days) |
| Inclination | 1.550 ± 0.004° |
| Longitude of perihelion | 359.48 ± 0.24 |
| Last perihelion | August 14, 1770 |
| Next perihelion | unknown/Lost |
| Physical characteristics | |
| Dimensions | ~4–30 km |
| Discovery | |
|---|---|
| Discovered by | MLS |
| Discovery site | Mount Lemmon Obs. |
| Discovery date | May 6, 2010 |
| Designations | |
| (529668) 2010 JL33 | |
| 2010 JL33 D/1770 L1 (Lexell) (possibly) | |
| Apollo · NEO · PHA | |
| Orbital characteristics | |
| Epoch 2022-Aug-09 (JD 2459800.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 22.75 yr (8,309 d) |
| Earliest precovery date | 4 June 1997 |
| Aphelion | 4.649 AU |
| Perihelion | 0.70971 AU |
| 2.6793 AU | |
| Eccentricity | 0.73512 |
| 4.39 yr (1,601 d) | |
| 250.87° | |
| 0° 13m 28.56s / day | |
| Inclination | 5.3772° |
| 52.452° | |
| 2.32° (good match for Lexell) | |
| 7 December 2023 | |
| 309.87° | |
| Earth MOID | 0.031 AU (12 LD) |
| Venus MOID | 0.00074 AU (110 thousand km) |
| Mars MOID | 0.039 AU |
| Jupiter MOID | 0.84 AU |
| TJupiter | 2.911 |
| Physical characteristics | |
Mean diameter | 1.778±0.034 km |
| 9.443±0.002 h | |
| 0.047±0.009 | |
| 17.9 | |
Lexell's Comet's 1770 passing still holds the record of closest observed approach of Earth by a comet. However, if approaches deduced from orbit calculations are included, it may have been beaten by a small sungrazing comet, P/1999 J6 (SOHO), which may have passed even closer at about 0.012 AU (1,800,000 km; 1,100,000 mi) from Earth on June 12, 1999, but the uncertainties are around ±1.5 million km as the P/1999 J6 approach was unobserved.