3200 Phaethon
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| Discovery A (http://cfa-www.harvard.edu/iau/lists/NumberedMPs.html) | |
|---|---|
| Discoverer | Simon Green and John K. Davies/IRAS |
| Discovery date | October 11, 1983 |
| Alternate designations | 1983 TB B (http://cfa-www.harvard.edu/iau/MPDes.html) |
| Category | Apollo asteroid, Mercury-crosser asteroid, Venus-crosser asteroid, Mars-crosser asteroid |
| Orbital elements C (http://asteroid.lowell.edu/) Epoch July 14, 2004 (JD 2453200.5) | |
| Eccentricity (e) | 0.890 |
| Semi-major axis (a) | 190.189 Gm (1.271 AU) |
| Perihelion (q) | 20.922 Gm (0.140 AU) |
| Aphelion (Q) | 359.456 Gm (2.403 AU) |
| Orbital period (P) | 523.586 d (1.43 a) |
| Mean orbital speed | 26.42 km/s |
| Inclination (i) | 22.169° |
| Longitude of the ascending node (Ω) | 265.427° |
| Argument of perihelion (ω) | 321.978° |
| Mean anomaly (M) | 200.798° |
| Physical characteristics | |
| Dimensions | 5.1 km |
| Mass | 1.4×1014 kg |
| Density | 2 ? g/cm³ |
| Surface gravity | 0.0014 m/s² |
| Escape velocity | 0.0027 km/s |
| Rotation period | ? d |
| Spectral class | B-type asteroid |
| Absolute magnitude | 14.6 |
| Albedo | 0.1 ? |
| Mean surface temperature | ~247 K |
3200 Phaethon (sometimes incorrectly spelled Phaeton) is an Apollo and Mercury-, Venus- and Mars-crosser asteroid with unusual properties, and may be an extinct comet.
Simon 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. IAUC 3881 soon 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.
Phaethon's most remarkable distinction is that it approaches the Sun closer than any other numbered asteroid; its perihelion is only 0.140 AU —, which is 58% of Mercury's orbital radius). The surface temperature at perihelion could reach ~1025 K. For this reason, it was named after the Greek myth of Phaëton, son of the sun god Helios.
Phaethon's attributes (orbit, size, reflectivity, and association with an annual meteor shower) can be argued as being cometary, except that Phaethon has never been caught exhibiting a coma, gas jets, or dust trail. Thus it is classified as an Apollo asteroid but is believed to be an inactive or extinct comet nucleus.
Phaethon is classified as a B-type asteroid because it is composed of dark material; this too fits well with the cometary origin hypothesis. It measures 5.10 km in diameter.
Phaethon will approach relatively close to the Earth on December 14, 2093, passing within 0.0194 AU (2.9 Gm).
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| (For a complete listing, see: List of asteroids. For pronunciation, see: Pronunciation of asteroid names.) |