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Contents: Near Earth Objects | Asteroids
Near-Earth Objects: As of Sept., 2007 there were 884 known PHAs.
* AU = Astronomical Unit - Approximate distanced from the earth to the sun The most potentially dangerous asteroid is 1950 DA. About 1 km in diameter and projected to have a 1 in 300 chance of hitting the earth in 2880.
Small Asteroids come close relatively often: A small near-Earth asteroid (NEA), discovered in March 2004 by the NASA-funded LINEAR asteroid survey, will make the closest approach to Earth ever recorded. There is no danger of a collision with the Earth during this encounter. LD = Lunar Distance - distance between Earth and the Moon - 384,401 km (238,856 mi.) The object, designated 2004 FH, is roughly 30 meters (100 feet) in diameter and will pass just 43,000 km (26,500 miles, or about 3.4 Earth diameters) above the Earth's surface in 2004. On average, objects about the size of 2004 FH pass within this distance roughly once every two years, but most of these small objects pass by undetected. This particular close approach is unusual only in the sense that scientists know about it. The fact that an object as small as asteroid 2004 FH has been discovered now is mostly a matter of perseverance by the LINEAR team, which is funded by NASA to search for larger kilometer-sized NEAs, but also routinely detect much smaller objects. May-July 2004 Earth-asteroid encounters
Source: SpaceWeather.com/ Large Asteroids: Most of these are in the asteroid belt between mars and jupiter and in no danger of hitting earth.
As of 2004 there were 26 known asteroids larger than 200 km in diameter. Chiron was discovered in 1977. It lies between Saturn and Uranus and occasionally passes within the orbit of Saturn. At first thought to be a comet or asteroid it is now considered a "planetoid" or small planet-like body. It is 170 km in diameter. No. Name Distance (km) Radius (km) Mass Discoverer Date ---- -------- ------ ------ ----- ---------- ----- 2062 Aten 144514 0.5 ? Helin 1976 3554 Amun 145710 ? ? Shoemaker 1986 1566 Icarus 161269 0.7 ? Baade 1949 433 Eros 172800 33x13x13 Witt 1898 1862 Apollo 220061 0.7 ? Reinmuth 1932 2212 Hephaistos 323884 4.4 ? Chernykh 1978 951 Gaspra 330000 8 ? Neujmin 1916 4 Vesta 353400 265 3.0e20 Olbers 1807 3 Juno 399400 123 ? Harding 1804 15 Eunomia 395500 136 8.3e18 De Gasparis 1851 1 Ceres 413900 466 8.7e20 Piazzi 1801 2 Pallas 414500 261 3.18e20 Olbers 1802 243 Ida 428000 35 ? ? 1880? 52 Europa 463300 156 ? Goldschmidt 1858 10 Hygiea 470300 215 9.3e19 De Gasparis 1849 511 Davida 475400 168 ? Dugan 1903 911 Agamemnon 778100 88 ? Reinmuth 1919 2060 Chiron 2051900 85 ? Kowal 1977Source: Asteroids at seds.lpl.arizona.edu
Kuiper Belt Objects (KBOs) Name Orbit Diameter Quaoar (2002 LM60) 42 AU 1250 km 800 mi Orcus (2004 DW) 45 AU 2005 FY9 700-1000 mi 2003 UB313 > 100 3000 km 1,850 mi See Planets: Planetoids at NASA.
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