3200 Phaethon

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3200 Phaethon
Asteroid Phaethon 25dec2010 stack.jpg
Asteroid (3200) Phaethon imaged on December 25, 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 December 9, 2014 (JD 2457000.5)
Aphelion 2.4023055 AU (359.37979 Gm)
Perihelion 0.1400373 AU (20.94928 Gm)
1.2711714 AU (190.16453 Gm)
Eccentricity 0.889836
1.43326 a (523.4854325174181 d)
19.98 km/s (12.41 mi/s)
Inclination 22.23995071185812°
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 Apollo 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 formally 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, and it later received the numerical designation and name 3200 Phaethon in 1985.

Orbital characteristics[edit]

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 as a result of its high orbital eccentricity. The surface temperature at perihelion could reach around 1,025 K (750 °C; 1,390 °F).

Physical characteristics[edit]

Phaethon is an asteroid with fairly unusual characteristics in that its orbit more closely resembles that of a comet than an asteroid; it 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 its discovery, several other objects were found exhibiting mixed cometary and asteroidal features, 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 found to be brighter than expected.[9][10] During its approach, the STEREO-A spacecraft detected an unexpected brightening, roughly 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: September 3, 2014; arc: 30.89 years). Jet Propulsion Laboratory. Retrieved October 14, 2014. 
  2. ^ JPL Small-Body Database Search Engine results for asteroids with q<0.141 AU Retrieved September 5, 2011. 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 Sutherland, Paul (September 10, 2013). "Why an asteroid is crumbling into meteor dust". Skymania.com. Retrieved September 10, 2013. 
  7. ^ Whipple, F. L. (October 25, 1983). Marsden, B. G., ed. "1983 TB and the Geminid Meteors". IAU Circular 3881. 1. Bibcode:1983IAUC.3881....1W. 
  8. ^ "(3200) Phaethon". NEODyS-2. University of Pisa Department of Mathematics. Retrieved May 18, 2009. 
  9. ^ Shanklin, Jonathan (2009). "Comet Section: 2009 News". British Astronomical Association. Retrieved September 20, 2009. 
  10. ^ Battams, K.; Watson, A. (June 2009). "(3200) Phaethon". IAU Circular 9054. 3. Bibcode:2009IAUC.9054....3B. 

External links[edit]

Media related to 3200 Phaethon at Wikimedia Commons