 Radar image of 3200 Phaethon taken by Arecibo, December 17, 2017 | |
| Discovery | |
|---|---|
| Discovered by | |
| Discovery date | October 11, 1983 |
| Designations | |
| (3200) Phaethon | |
| Pronunciation | /ˈfeɪ.əθɒn/ |
Named after | Phaëthon |
| 1983 TB | |
| Adjectives | Phaethonian/feɪəˈθoʊniən/[2] |
| Orbital characteristics[1] | |
| Epoch April 27, 2019 (JD 2458000.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 12,941 days (35.43 yr) |
| Aphelion | 2.4028 AU (359 million km) |
| Perihelion | 0.13998 AU (20.9 million km) |
| 1.2714 AU (190 million km) | |
| Eccentricity | 0.88990 |
| 523.6 days (1.434 yr) | |
Averageorbital speed | 19.9 km/s (45,000 mph) |
| 313.94° | |
| 0° 41m 15.108s / day | |
| Inclination | 22.260° |
| 265.22° | |
| May 15, 2022[3] | |
| 322.19° | |
| Earth MOID | 0.01955 AU (2.92 million km) |
| Venus MOID | 0.0469 AU (7.02 million km)[4] |
| Jupiter MOID | 2.7375 AU (410 million km) |
| TJupiter | 4.510 |
| Physical characteristics | |
| Dimensions | 6.13±0.05 ×4.40±0.06 km[5] |
| 5.8 km (3.6 mi)[6] | |
| 3.604hours (0.1502 d)[1] | |
| 0.1066±0.011[1] | |
| F-type asteroid[1][7] | |
| 10.7 (December 14, 2017) | |
| 14.6[1] | |
3200 Phaethon (/ˈfeɪ.əˌθɒn/; previously sometimes spelledPhæton),provisionally designated1983 TB, is anactive[8]Apollo asteroid with an orbit that brings it closer to theSun than any othernamed asteroid (though there are numerous unnamed asteroids with smaller perihelia, such as(137924) 2000 BD19).[9] For this reason, it was named after theGreek Hero,Phaëthon, son of the sun godHelios. It is 5.8 km (3.6 mi) indiameter[6] and is theparent body of theGeminidsmeteor shower of mid-December. With anobservation arc of 35+ years, it has a very welldetermined orbit.[1] The 2017 Earth approach distance of about 10 million km was known with an accuracy of ±700 m.[1]
Phaethon was the first asteroid to be discovered using images from a spacecraft.Simon F. Green andJohn K. Davies discovered it in images from October 11, 1983, while searchingInfrared Astronomical Satellite (IRAS) data for moving objects. It was formally announced on October 14 in IAUC 3878 along with optical confirmation byCharles T. Kowal, who reported it to be asteroidal in appearance. Its provisional designation was1983 TB, and it later received the numerical designation and name3200 Phaethon in 1985.
Phaethon is categorized as anApollo asteroid, as its orbitalsemi-major axis is greater than that of theEarth's at 1.27 AU (190 million km; 118 million mi). It is also suspected to be a member of thePallas family of asteroids.[10]
Its most remarkable distinction is that it approaches the Sun closer than any other named asteroid: itsperihelion is only 0.14 AU (20.9 million km; 13.0 million mi) — less than half ofMercury's perihelial distance. It is aMercury-,Venus-,Earth-, andMars-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).
Phaethon is a possible candidate for detectinggeneral relativistic and/or solaroblateness effects in its orbital motion due to the frequent close approaches to the Sun.[11] The Apollo asteroids(155140) 2005 UD and(225416) 1999 YC share similar orbits with Phaethon, suggesting a possible common breakup origin.[12][13]
Phaethon is categorized as apotentially hazardous asteroid (PHA),[1][14] but that does not mean there is a near-term threat of an impact. It is a potentially hazardous asteroid merely as a result of its size (absolute magnitudeH ≤ 22) and Earthminimum orbit intersection distance(Earth MOID ≤ 0.05 AU).[15] The Earth minimum orbit intersection distance (E-MOID) is 0.01945 AU (2,910,000 km; 1,808,000 mi), which is defined by the shortest distance between the orbit of Phaethon and the orbit of Earth.[1] With a 30+ year observation arc, the orbit of Phaethon is very well understood with very small uncertainties.[1] Close approaches of Phaethon are well constrained for the next 400 years.[11]
| PHA | Date | Approach distance inlunar distances | Abs. mag (H) | Diameter (C) (m) | Ref (D) | ||
|---|---|---|---|---|---|---|---|
| Nominal (B) | Minimum | Maximum | |||||
| (143651) 2003 QO104 | 1981-05-18 | 2.761 | 2.760 | 2.761 | 16.0 | 1333–4306 | data |
| 2014 LJ21 | 1989-08-01 | 7.034 | 6.843 | 7.224 | 16.0 | 1333–4306 | data |
| 4179 Toutatis | 1992-12-08 | 9.399 | 9.399 | 9.399 | 15.30 | 2440–2450 | data |
| 4179 Toutatis | 2004-09-29 | 4.031 | 4.031 | 4.031 | 15.30 | 2440–2450 | data |
| (159857) 2004 LJ1 | 2038-11-16 | 7.719 | 7.719 | 7.719 | 15.4 | 1746–4394 | data |
| (4953) 1990 MU | 2058-06-05 | 8.986 | 8.984 | 8.988 | 14.1 | 3199–10329 | data |
| 4179 Toutatis | 2069-11-05 | 7.725 | 7.724 | 7.725 | 15.30 | 2440–2450 | data |
| (52768) 1998 OR2 | 2079-04-16 | 4.611 | 4.611 | 4.612 | 15.8 | 1462–4721 | data |
| (415029) 2011 UL21 | 2089-06-25 | 6.936 | 6.935 | 6.938 | 15.7 | 1531–4944 | data |
| 3200 Phaethon | 2093-12-14 | 7.714 | 7.709 | 7.718 | 14.6 | 4900–5300 | data |
| (52768) 1998 OR2 | 2127-04-16 | 6.536 | 6.510 | 6.563 | 15.8 | 1462–4721 | data |
| (A) This list includes near-Earth approaches of less than 10lunar distances (LD) of objects withH brighter than 16. (B)Nominal geocentric distance from the center of Earth to the center of the object (Earth has aradius of approximately 6,400 km). (C) Diameter: estimated, theoretical mean-diameter based onH andalbedo range between X and Y. (D) Reference: data source from theJPL SBDB, withAU converted into LD (1 AU≈390 LD) (E) Color codes: unobserved at close approach observed during close approach upcoming approaches | |||||||
Phaethon is an asteroid with fairly unusual characteristics in that its orbit more closely resembles that of acomet than an asteroid; it has been referred to as a "rock comet".[16] In studies performed byNASA'sSTEREO spacecraft in 2009 and 2012, rapid brightening and dust tail have been observed.[17][18][19]It is possible that the Sun's heat is causing fractures similar tomudcracks in adry lake bed.[20] This occurs because Phaethon's orbit takes it closer to the Sun than any other named asteroid (0.14 AU atperihelion) causing extreme heating and enoughsolar radiation pressure to push any separated pieces off the asteroid's surface. Since its discovery, several other objects were found exhibiting mixed cometary and asteroidal features, such as133P/Elst–Pizarro, leading to a new class of objects dubbed "active asteroids".[8]
In 2018, observations revealed that Phaethon was blue in color. This is extremely rare, as most asteroids tend to be grey or red.[21][22] In 2020,polarimetric study revealed Phaethon has a surface with steep slopes covered by a mix ofregolith with larger pebbles.[23] Phaethon's composition fits the notion of its cometary origin; it is classified as aF-type asteroid because it is composed of dark material[1][7] or a B-type asteroid because of its blue color.[24] In 2022 it was shown[25][26] how Phaethon's blue color and its rock-comet-like emission activity can be explained by the effects of the intense solar heating at perihelion causing sublimation of any darkish-red refractory organic, nano-phase iron (nFe0), and pyroxene materials on its surface.
Analysis of a mid-infrared spectral emissivity spectrum from theSpitzer Space Telescope showed Phaethon to be linked to the rare Yamato-type (CY)carbonaceous chondrites.[27] This link appears speculative and partial.[28] Further analysis of this spectrum confirmed the presence of Mg-richolivine,carbonates, and Fe-sulfides. These minerals decompose at the temperatures that Phaethon reaches at perihelion, resulting in outgassing, in a process calledthermal decomposition. It is believed that this process leads to dust ejection and can explain the formation of the Geminid meteor stream.
Shortly after its discovery,Fred Whipple noted that Phaethon'sorbital elements were extremely similar to those of theGeminid meteor shower,[29] indicating that Phaethon was the meteor shower's long-sought parent body.
DESTINY+ (Demonstration and Experiment of Space Technology for INterplanetary voYage Phaethon fLyby dUSt science) is a planned mission to fly by 3200 Phaethon, as well as various minor bodies originating from it. The spacecraft is being developed by the Japanese space agencyJAXA and will demonstrate advanced technologies for future deep space exploration. DESTINY+ is planned to be launched no earlier than 2028.[30]
Phaethon approached to 0.120895 AU (18,085,600 km; 11,237,900 mi) of Earth on December 10, 2007,[1] and was detected byradar atArecibo.[11] When Phaethon came to perihelion in July 2009, it was found to be brighter than expected.[31][32] During its approach, theSTEREO-A spacecraft detected an unexpected brightening, roughly by a factor of two.[16]
On December 16, 2017, at 23:00 UT, Phaethon passed 0.06893169 AU (10,312,034 km; 6,407,601 mi) from Earth (27lunar distances).[1] The Earth approach distance was known with a3-sigma precision of ±700 m.[1][a] This was the best opportunity to date for radar observations byGoldstone andArecibo, with a resolution of 75 meters/pixel (246 feet/pixel).[11]
The asteroid was bright enough to see in small telescopes, peaking at magnitude 10.8 between December 13–15 while dimming slightly to magnitude 11 on December 16 at closest approach.[33] Arecibo made observations of Phaethon from December 15–19.[6] It will not make an Earth approach closer than the 2017 passage until December 14, 2093, when it will pass 0.01981 AU (2,964,000 km; 1,841,000 mi) from Earth.[1][34]
| International | |
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| Other | |
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