3200 Phaethon
From Wikipedia, the free encyclopedia
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Discovery
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| Discovered by | Simon Green and John K. Davies/IRAS |
| Discovery date | October 11, 1983 |
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Designations
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| Alternative names | 1983 TB |
| Minor planet category |
Apollo asteroid, Mercury-crosser asteroid, Venus-crosser asteroid, Mars-crosser asteroid |
| Epoch July 14, 2004 (JD 2453200.5) | |
| Aphelion | 359.456 Gm (2.403 AU) |
| Perihelion | 20.922 Gm (0.140 AU) |
| Semi-major axis | 190.189 Gm (1.271 AU) |
| Eccentricity | 0.890 |
| Orbital period | 523.586 d (1.43 a) |
| Average orbital speed | 19.98 km/s |
| Mean anomaly | 200.798° |
| Inclination | 22.169° |
| Longitude of ascending node | 265.427° |
| Argument of perihelion | 321.978° |
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Physical characteristics
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| Dimensions | 5.1 km |
| Mass | 1.4×1014 kg |
| Mean density | 2 ? g/cm³ |
| Equatorial surface gravity | 0.0014 m/s² |
| Escape velocity | 0.0027 km/s |
| Rotation period | ? d |
| Albedo | 0.1 ? |
| Temperature | ~247 K |
| Spectral type | B-type asteroid |
| Absolute magnitude | 14.6 |
3200 Phaethon (pronounced /ˈfeɪəθɒn/ fay'-ə-thon, sometimes incorrectly spelled Phaeton) is an Apollo and Mercury-, Venus-, Earth- and Mars-crosser asteroid with unusual properties, and may be an extinct comet.
Simon F. Green and John K. Davies, while searching Infrared Astronomical Satellite (IRAS) data for moving objects, discovered 3200 Phaethon (1983 TB) in images from October 11, 1983. 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. It was the first asteroid to be discovered by a spacecraft. It measures 5.10 km in diameter.
Phaethon's most remarkable distinction is that it approaches the Sun closer than any other numbered asteroid; its perihelion is only 0.140 AU — less than half Mercury's perihelion distance. The surface temperature at perihelion could reach ~1025 K, or 1400 F. For this reason, it was named after the Greek myth of Phaëton, son of the sun god Helios.
Phaethon's attributes can be argued as being cometary, except that Phaethon has never been caught exhibiting a coma, gas jets, or dust trail. However IAUC 3881 soon after discovery of 3200 Phaethon reported Fred Whipple's observation that "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". Phaethon thus turned out to be the long-sought parent body of the Geminids meteor shower of mid-December. It is classified as an Apollo asteroid because of its orbital qualities, also much in common with comets and is also classified as a B-type asteroid because it is composed of dark material; this too fits well with the cometary origin hypothesis. There are several asteroid/comet mixed type objects now known for sure. See 133P/Elst-Pizarro for example.
Phaethon approached to 18.1 Gm on December 10, 2007. It will draw nearer in 2017, 2050, 2060, and closer still on December 14, 2093, passing within 0.0198 AU (3.0 Gm).
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