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4179 Toutatis ( ) is an Apollo, Alinda, and Mars-crosser asteroid with a chaotic orbit produced by a 3:1 resonance with the planet Jupiter, a 1:4 resonance with the planet Earth, and frequent close approaches to the terrestrial planets, including Earth.〔 It is listed as a potentially hazardous object,〔 although the probability of a collision with Earth is minute.〔 On December 12, 2012 at 06:40 UT Toutatis passed within about 18 lunar distances of Earth.〔〔(NEO Earth Close Approaches )〕 On December 13, the Chinese lunar probe Chang'e 2, launched in 2010 on a lunar mission, flew by Toutatis at a distance of 3.2 kilometers and a relative velocity of 10.73 km/s.〔 Toutatis will approach Earth again in 2016, but will not make another notably close approach until 2069. == Properties == 4179 Toutatis was first sighted on February 10, 1934, as object 1934 CT, but lost soon afterwards.〔 It remained a lost asteroid for several decades until it was rediscovered on January 4, 1989, by Christian Pollas, and was named after the Celtic god of tribal protection Toutatis (Teutates). The spectral properties suggest that this is an S-type, or stony asteroid, consisting primarily of silicates. It has a moderate Bond albedo of 0.13.〔 Radar imagery shows that Toutatis is a highly irregular body consisting of two distinct "lobes", with maximum widths of about 4.6 km and 2.4 km respectively. It is hypothesized that Toutatis formed from two originally separate bodies which coalesced at some point, with the resultant asteroid being compared to a "rubble pile". Its rotation combines two separate periodic motions into a non-periodic result; to someone on the surface of Toutatis, the Sun would seem to rise and set in apparently random locations and at random times at the asteroid's horizon. It has a rotation period around its long axis (Pψ) of 5.38 days. This long axis is precessing with a period (Pφ) of 7.38 days.〔 The asteroid may have lost most of its original angular momentum and entered into this tumbling motion as a result of the YORP effect.〔 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「4179 Toutatis」の詳細全文を読む スポンサード リンク
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