Comet Encke
Comet Encke /ˈɛŋki/, or Encke's Comet (official designation: 2P/Encke), is a periodic comet that completes an orbit of the Sun once every 3.3 years. (This is the shortest period of a reasonably bright comet; the faint main-belt comet 311P/PanSTARRS has a period of 3.2 years.) Encke was first recorded by Pierre Méchain on 17 January 1786, but it was not recognized as a periodic comet until 1819 when its orbit was computed by Johann Franz Encke. Like Halley's Comet, it is unusual in its being named after the calculator of its orbit rather than its discoverer. Like most comets, it has a very low albedo, reflecting only 4.6% of the light its nucleus receives, although comets generate a large coma and tail that can make them much more visible during their perihelion (closest approach to the Sun). The diameter of the nucleus of Encke's Comet is 4.8 km.
| Discovery | |
|---|---|
| Discovered by | Pierre Méchain; Johann Franz Encke (recognition of periodicity) |
| Discovery date | 17 January 1786 |
| Designations | |
Alternative designations | 1786 I; 1795; 1805; 1819 I; 1822 II; 1825 III; 1829; 1832 I; 1835 II; 1838; 1842 I; 1845 IV |
| Orbital characteristics | |
| Epoch | 2023 September 13 |
| Aphelion | 4.098 AU |
| Perihelion | 0.33960 AU |
| Semi-major axis | 2.2187 AU |
| Eccentricity | 0.8469 |
| Orbital period | 3.30 yr 3y 3m 27d (perihelion to perihelion) |
| Max. orbital speed | 69.5 km/s (250,000 km/h) |
| Inclination | 11.34° |
| Argument of periapsis | 187.3° |
| Last perihelion | 22 October 2023 |
| Next perihelion | 9 February 2027 |
| TJupiter | 3.025 |
| Earth MOID | 0.17 AU (25 million km) |
| Physical characteristics | |
| Dimensions | 4.8 km |