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1866 Sisyphus ( ), provisional designation 1972 XA, is stony, binary asteroid, classified as near-Earth object. It measures about 7 kilometers in diameter and is the largest member of the Apollo asteroids, a subgroup of near-Earth asteroids which cross the orbit of Earth. It was discovered by astronomer Paul Wild at Zimmerwald Observatory near Bern, Switzerland on 5 December 1972.〔〔 The S-type asteroid orbits the Sun at a distance of 0.9–2.9 AU once every 2 years and 7 months (952 days). It has a rotation period of 2.4 hours and a geometric albedo of 0.150. Its orbit is highly eccentric (0.54) and tilted by 41 degrees to the plane of the ecliptic. The asteroid's ''Earth minimum orbit intersection distance'' (MOID) is .〔 In 1985, this object was detected with radar from the Arecibo Observatory at a distance of 0.25 AU. The measured radar cross-section was 8 square kilometers.〔 During the radar observations, a small satellite was detected, although its existence was not reported until December 2007. As a result, little is known about the moon. The asteroid is named after the Sisyphus of Greek mythology and refers to the cruel king of Ephyra, punished by being given the task of rolling a large stone up to a hill in the underworld, only to have it roll down again each time he neared the top.〔 ''Sisyphus'' will pass from Earth on November 24, 2071,〔 and will peak at roughly apparent magnitude 9.3 on November 26, 2071.〔 When it was discovered it peaked at magnitude 9.0 on November 25, 1972. It is one of the brightest near-Earth asteroids. With a measured mean diameter in the range of 5.7–8.9 kilometers, it the largest of the Earth-crossing asteroids, comparable in size to the Chicxulub object whose impact may have extinct the dinosaurs.〔 Larger near-Earth asteroids which are neither classified as Apollos nor Earth-crossers include 1036 Ganymed (32 km), 3552 Don Quixote (19 km), 433 Eros (17 km), and 4954 Eric (10.8 km). == See also == * Near Earth Object Camera * Near-Earth asteroids 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「1866 Sisyphus」の詳細全文を読む スポンサード リンク
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