3200 Phaethon

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3200 Phaethon
Asteroid Phaethon 25dec2010 stack.jpg
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
Named after
1983 TB
Orbital characteristics
Epoch July 14, 2004 (JD 2453200.5)
Aphelion 2.403 AU (359.5 Gm)
Perihelion 0.140 AU (20.9 Gm)
1.271 AU (190.1 Gm)
Eccentricity 0.890
1.43 a (523.586 d)
19.98 km/s (12.41 mi/s)
Inclination 22.169°
Physical characteristics
Dimensions 5.1 ± 0.2 km (3.17 ± 0.12 mi)[1]
3.604 hr[1]
Albedo 0.1066±0.011[1]
Temperature ~247 K
Spectral type
B-type asteroid

3200 Phaethon (/ˈf.əθɒn/ 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).[2] For this reason, it was named after the Greek myth of Phaëton, son of the sun god Helios. It is 5.1 ± 0.2 km (3.17 ± 0.12 mi) in mean diameter.[1]


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, as 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.[3]

Phaethon's most remarkable distinction is that it approaches the Sun closer than any other named asteroid: its perihelion is only 0.140 AU (20,900,000 km; 13,000,000 mi) — less than half of Mercury's perihelion distance. It is a Mercury-, Venus-, Earth-, and Mars-crosser. The surface temperature at perihelion could reach around 1,025 K (750 °C; 1,390 °F).

Physical characteristics[edit]

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".[4] In recent studies performed by NASA's STEREO spacecraft, dust tails have been observed,[5] and in 2010 Phaethon was detected ejecting dust.[6] It is possible that the Sun's heat is causing fractures similar to mudcracks in a dry lake bed.[6]

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.

Meteor shower[edit]

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".[7] In other words, Phaethon is the long-sought parent body of the Geminids meteor shower of mid-December.

Recent close approaches[edit]

Phaethon approached to 0.120895 AU (18,085,600 km; 11,237,900 mi) of Earth on December 10, 2007.[1] On December 10, 2017, it will pass 0.06893 AU (10,312,000 km; 6,407,000 mi) from Earth. Then on December 14, 2093, it will pass 0.0198 AU (2,960,000 km; 1,840,000 mi) from Earth.[1][8]

When Phaethon came to perihelion in July 2009, it was brighter than expected.[9][10] As Phaethon approached perihelion in June 2009, the STEREO-A spacecraft detected an unexpected brightening, by a factor of two.[4]


  1. ^ a b c d e f g "JPL Small-Body Database Browser: 3200 Phaethon (1983 TB)" (last observation: 2014-09-03; arc: 30.89 years). Jet Propulsion Laboratory. Retrieved 2014-10-14. 
  2. ^ 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).
  3. ^ "Exploding Clays Drive Geminids Sky Show?", 2010 October 12
  4. ^ a b Jewitt, David; Li, Jing (2010). "Activity in Geminid Parent (3200) Phaethon". The Astronomical Journal 140 (5): 1519. arXiv:1009.2710. Bibcode:2010AJ....140.1519J. doi:10.1088/0004-6256/140/5/1519. 
  5. ^ Jewitt, David; Li, Jing; Agarwal, Jessica (2013). "The Dust Tail of Asteroid (3200) Phaethon". The Astrophysical Journal Letters 771 (2): L36. arXiv:1306.3741. Bibcode:2013ApJ...771L..36J. doi:10.1088/2041-8205/771/2/L36. 
  6. ^ a b Paul Sutherland (2013-09-10). "Why an asteroid is crumbling into meteor dust". Retrieved 2013-09-10. 
  7. ^ Whipple, F. L. (1983). "1983 TB and the Geminid Meteors". IAU Circulars 3881: 1. Bibcode:1983IAUC.3881....1W. Retrieved 2009-05-18. 
  8. ^ "NEODyS (3200) Phaethon". Department of Mathematics, University of Pisa, ITALY. Retrieved 2009-05-18. 
  9. ^ Jonathan Shanklin (2009). "BAA Comet section Old News (2009)". British Astronomical Association Comet Section. Retrieved 2009-09-20. 
  10. ^ Battams, K.; Watson, A. (2009). "(3200) Phaethon". IAU Circulars 9054: 3. Bibcode:2009IAUC.9054....3B. 

External links[edit]