Space Studies of the Outer Planets
Up to the time of Galileo six planets and one satellite — the Moon — were known; during the time of telescopic observations—from the first observations by Galileo in 1610 up to our times, that is, for nearly four centuries — three planets, 32 satellites, the asteroids, comets, the Saturnian rings, the Uranian rings, and the Neptunian arcs were discovered. By means of spacecraft during about ten years—between 1979 and 1989— the Jovian rings and 28 satellites in the systems of the giant planets were discovered. As a result of this “productivity” of the space projects the “epoch of the great geographical discoveries” within the known limits of the solar system had been swiftly concluded. After Voyager-2 in 1989 had flown past Neptune only Pluto remained to be visited in the solar system and one can hardly expect the existence of a developed satellite system near it. This means that the number of known satellites of the main planets of a size of more than 100 km is now practically fixed.
KeywordsSolar System Giant Planet Outer Planet Space Study Abstract Journal
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