Comet Encke
The comet with the shortest period of any well-known comet, and the source of the Taurids and their bright fireballs.
Key facts
- Designation
- 2P/Encke
- Type
- Jupiter-family comet (an unusual one, almost free of Jupiter)
- Orbital period
- 3.3 years
- Closest to the Sun
- 0.34 AU (about 50 million km), inside Mercury's orbit
- Farthest from the Sun
- 4.1 AU, inside Jupiter's orbit
- Tilt of orbit
- about 12°
- Nucleus
- about 4.8 km across
- Discovered
- by Pierre Méchain in Paris on 17 January 1786; its orbit was worked out by Johann Encke in 1819
- Returns
- seen at every return since 1818; it was at perihelion in October 2023 and is due again in early 2027
Orbit
Encke goes round the Sun every 3.3 years, the shortest period of any comet that is easily seen. Its orbit stays wholly inside Jupiter's, which is rare: most short-period comets cross Jupiter's path and are thrown about by it. Close to the Sun it passes inside Mercury's orbit. Its dust meets Earth at a fairly slow 27 to 30 km/s.
Size and nature
The nucleus is about 4.8 km across, with a dark surface and only small active areas. Because it has passed the Sun thousands of times, much of its ice is buried under dust. In 2007 a spacecraft watching the Sun saw a burst of solar wind tear its tail away, and it soon grew a new one.
History
Pierre Méchain first saw it in 1786, Caroline Herschel found it again in 1795, and Jean-Louis Pons in 1818. The German astronomer Johann Encke showed that these were one comet returning every 3.3 years, only the second comet known to be periodic, so it bears his name. Encke also noticed that it returned a few hours early each time. This was later explained by jets of gas acting like small rockets, the first evidence that comets are icy bodies that lose material.
Meteor showers
Encke lies within a broad stream of debris called the Taurid complex, built up over perhaps 20,000 years and probably from the break-up of a larger comet. Earth passes through it in October and November, giving the Southern and Northern Taurids, and again in June, in daylight, giving the Beta Taurids and Zeta Perseids that only radar can detect. The Taurids are famous for slow, bright fireballs, and in some years, such as 2005 and 2015, Earth meets a swarm of larger particles.
Missions
The CONTOUR spacecraft was meant to fly past Encke in 2003, but it was lost soon after launch in 2002.
Its meteor showers
- The Southern Taurids peak broad maximum from about 10 October to early November (often quoted around 5 November); about 5 an hour at best; 27 km/s
- The Northern Taurids peak around 11–12 November; about 5 an hour at best; 29 km/s
- The Daytime Beta Taurids peak around 28 June; about moderate on radio; very few seen by eye an hour at best; 29 km/s
- The Daytime Zeta Perseids peak around 9 June; about strong on radio; very few seen by eye an hour at best; 29 km/s
- The Chi Orionids peak around 2–10 December (historically listed); about 2–3 an hour at best; 28 km/s
Space missions
- CONTOUR A mission to compare comets that was lost six weeks after launch.
Key dates
| Date | What happened |
|---|---|
| 17 January 1786 | Pierre Méchain discovered the comet later named after Johann Encke. |
Did you know?
Encke's Comet has been seen at more returns than any other comet: over 60 since 1786.
The MESSENGER spacecraft found that Mercury gains calcium-rich vapour each time it crosses Encke's dust stream.
Some astronomers have suggested the Tunguska object of 1908 came from the Taurid complex, but this has never been shown.