Dione(redirected from Dione (disambiguation))
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Dione, in astronomy
Dione (dīōˈnē), in astronomy, one of the named moons, or natural satellites, of Saturn. Also known as Saturn IV (or S4), Dione is 695 mi (1,120 km) in diameter, orbits Saturn at a mean distance of 234,500 mi (377,400 km), and has an orbital period of 2.737 earth days—the rotational period is unknown but is assumed to be the same as the orbital period. It was discovered in 1684 by the Italian-French astronomer Gian Domenico Cassini. Aside from Titan, Dione is the densest of Saturn's satellites; it is believed to be composed primarily of water ice with a considerable fraction of denser material, such as silicate rock. The trailing hemisphere is more heavily cratered than the leading hemisphere, which is the reverse of the cratering on most of the other Saturnian satellites. Another moon, Helene, is co-orbital with Dione; that is, it orbits Saturn at the same distance as Dione, and precedes Dione by about 60°. Dione also forms a satellite pair with Enceladus; that is, the two moons interact gravitationally.
Dione, in Greek religion and mythology
Dione, in Greek religion and mythology, earth goddess. In some legends she is the daughter of Oceanus and Tethys; in others she is a Titaness, born to Uranus and Gaea. In yet another version she is the mother of Aphrodite. Her name is the feminine form of Zeus. Her cult was associated with the oracle at Dodona.
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Dione(dÿ-oh -nee) A satellite of Saturn, discovered in 1684 by Giovanni Domenico Cassini. It has a diameter of 1118 km and density of 1.4 g cm–3, and is slightly larger than the satellite Tethys. An important characteristic of Dione is the nonuniformity of its brightness. The trailing hemisphere is dark, with an albedo of approximately 0.3, whereas the brightest features of the leading hemisphere have an albedo of approximately 0.6. Only Iapetus, of the Saturn system, displays a greater variation of brightness between the hemispheres. The surface shows evidence of a number of craters of 30–40 km, with a few large craters 165 km or more in diameter. There are some broad ridges in the southern part of the heavily cratered plains, with a long linear valley more than 500 km in length near the south pole. Dione's relatively high density compared with the neighboring satellites indicates a higher rock content of the interior. The most prominent feature is Amata, a crater 240 km in diameter associated with a system of bright wispy features that extend over the trailing hemisphere. The bright streaks on the surface first imaged by the two Voyager probes have been shown by the Cassini probe to be a vast system of linear features scarring the satellite's surface. A minor satellite, Helene, has been discovered to share the orbit of Dione. See also Table 2, backmatter.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006
A satellite of Saturn that orbits at a mean distance of 2.35 × 105 miles (3.78 × 105 kilometers) and has a diameter of about 700 miles (1120 kilometers).
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.