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The planet Jupiter has a system of rings known as the rings of Jupiter or the Jovian ring system. It was the third ring system to be discovered in the Solar System, after those of Saturn and Uranus. It was first observed in 1979 by the ''Voyager 1'' space probe〔 and thoroughly investigated in the 1990s by the ''Galileo'' orbiter.〔 It has also been observed by the Hubble Space Telescope and from Earth for the past 23 years.〔 Ground-based observations of the rings require the largest available telescopes.〔 The Jovian ring system is faint and consists mainly of dust.〔〔 It has four main components: a thick inner torus of particles known as the "halo ring"; a relatively bright, exceptionally thin "main ring"; and two wide, thick and faint outer "gossamer rings", named for the moons of whose material they are composed: Amalthea and Thebe.〔 The main and halo rings consist of dust ejected from the moons Metis, Adrastea, and other unobserved parent bodies as the result of high-velocity impacts.〔 High-resolution images obtained in February and March 2007 by the ''New Horizons'' spacecraft revealed a rich fine structure in the main ring.〔 In visible and near-infrared light, the rings have a reddish color, except the halo ring, which is neutral or blue in color.〔 The size of the dust in the rings varies, but the cross-sectional area is greatest for nonspherical particles of radius about 15 μm in all rings except the halo.〔 The halo ring is probably dominated by submicrometre dust. The total mass of the ring system (including unresolved parent bodies) is poorly known, but is probably in the range of 1011 to 1016 kg.〔 The age of the ring system is not known, but it may have existed since the formation of Jupiter.〔 A ring could possibly exist in Himalia's orbit. One possible explanation is that a small moon had crashed into Himalia and the force of the impact caused material to blast off Himalia.〔("Lunar marriage may have given Jupiter a ring" ), New Scientist, March 20, 2010, p. 16.〕 ==Discovery and structure== Jupiter's ring system was the third to be discovered in the Solar System, after those of Saturn and Uranus. It was first observed in 1979 by the ''Voyager 1'' space probe. It comprises four main components: a thick inner torus of particles known as the "halo ring"; a relatively bright, exceptionally thin "main ring"; and two wide, thick and faint outer "gossamer rings", named after the moons of whose material they are composed: Amalthea and Thebe. The principal attributes of the known Jovian Rings are listed in the table.〔〔〔 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「Rings of Jupiter」の詳細全文を読む スポンサード リンク
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