Asteroid (3200) Phaethon imaged on 25 Dec 2010 with the 37 cm F14 Cassegrain telescope of Winer Observatory, Sonoita (MPC 857) by Marco Langbroek.
|Discovered by||Simon Green and
John K. Davies/IRAS
|Discovery date||October 11, 1983|
|Alternative names||1983 TB|
|Minor planet category||Apollo asteroid,
|Epoch July 14, 2004 (JD 2453200.5)|
|Aphelion||2.403 AU (359.456 Gm)|
|Perihelion||0.140 AU (20.922 Gm)|
|Semi-major axis||1.271 AU (190.189 Gm)|
|Orbital period||1.43 a (523.586 d)|
|Average orbital speed||19.98 km/s|
|Longitude of ascending node||265.427°|
|Argument of perihelion||321.978°|
|Rotation period||3.604 hr|
|Spectral type||B-type asteroid|
|Absolute magnitude (H)||14.6|
3200 Phaethon (// FAY-ə-thon, sometimes incorrectly spelled Phaeton) is an asteroid with an unusual orbit that brings it closer to the Sun than any other named asteroid (though there are several unnamed asteroids, including three numbered ones, with smaller perihelia, e.g. (137924) 2000 BD19). For this reason, it was named after the Greek myth of Phaëton, son of the sun god Helios. It is 5.10 km in mean diameter.
Phaethon was the first asteroid to be discovered using images from a spacecraft. Simon F. Green and John K. Davies discovered it in images from October 11, 1983 while searching Infrared Astronomical Satellite (IRAS) data for moving objects. It was announced on October 14 in IAUC 3878 along with optical confirmation by Charles T. Kowal, who reported it to be asteroidal in appearance. Its provisional designation was 1983 TB.
It is categorized as an Apollo asteroid (because its semi-major axis is greater than that of the Earth's and its perihelion is less than 1.017 AU). It is also suspected to be a member of the Pallas family of asteroids.
Phaethon's most remarkable distinction is that it approaches the Sun closer than any other named asteroid: its perihelion is only 0.140 AU — less than half of Mercury's perihelion distance. It is a Mercury-, Venus-, Earth-, and Mars-crosser. The surface temperature at perihelion could reach ~1025 K (750°C, 1400°F).
Phaethon is an asteroid with unusual characteristics in that its orbit looks more like that of a comet than an asteroid, and has been referred to as a "rock comet".  In recent studies done with NASA's STEREO spacecraft, dust tails have been observed  and in 2010, Phaethon was detected ejecting dust. It is possible that the Sun’s heat is causing fractures such as mudcracks in a dry lake bed.
Phaethon's composition fits the notion of its cometary origin; it is classified as a B-type asteroid because it is composed of dark material. Since Phaethon, several other objects showing mixed cometary and asteroidal features have been discovered, such as 133P/Elst–Pizarro.
Shortly after its discovery, Fred Whipple observed that the "orbital elements of 1983 TB shown on IAUC 3879 are virtually coincident with the mean orbital elements of 19 Geminid meteors photographed with the super-Schmidt meteor cameras". In other words, Phaethon is the long-sought parent body of the Geminids meteor shower of mid-December.
Recent close approaches
When Phaethon came to perihelion in July 2009, it was brighter than expected. As Phaethon approached perihelion in June 2009, the STEREO-A spacecraft detected an unexpected brightening, by a factor of two.
- "JPL Small-Body Database Browser: 3200 Phaethon (1983 TB)". Jet Propulsion Laboratory. 2012-02-25 last obs. Retrieved 2012-06-19.
- JPL Small-Body Database Search Engine results for asteroids with q<0.141 AU Retrieved 2011-09-05. Take notice of the orbit condition number (the lower the number, the lower the orbit's uncertainty).
- "Exploding Clays Drive Geminids Sky Show?", 2010 October 12
- Jewitt, David; Li, Jing (2010). "Activity in Geminid Parent (3200) Phaethon". arXiv:1009.2710.
- Jewitt, David; Li, Jing (2013). "The Dust Tail of Asteroid (3200) Phaethon". arXiv:1306.3741.
- Paul Sutherland (2013-09-10). "Why an asteroid is crumbling into meteor dust". Retrieved 2013-09-10.
- Brian G. Marsden (1983-10-25). "IAUC 3881: 1983 TB and the Geminid Meteors 1983 SA; KR Aur". International Astronomical Union Circular. Retrieved 2009-05-18.
- "NEODyS (3200) Phaethon". Department of Mathematics, University of Pisa, ITALY. Retrieved 2009-05-18.
- Jonathan Shanklin (2009). "BAA Comet section Old News (2009)". British Astronomical Association Comet Section. Retrieved 2009-09-20.
- IAUC 9054 (2009 June 29)
- Orbital simulation from JPL (Java)
- "The Geminid Meteor Shower". NASA. 2004-12-06. Archived from the original on 25 November 2007. Retrieved 2007-11-08.
- (3200) Phaethon discussed on a blog
- ScienceCasts: Rock Comet Meteor Shower (Science@NASA YouTube channel : Nov 29, 2012)