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| | Dione, in astronomy. The Columbia Encyclopedia, Sixth Edition. 2001-05 |
 | | 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 daysthe rotational period is unknown but is assumed to be the same as the orbital period. |
 | | Aside from Titan, Dione is the densest of Saturns satellites; it is believed to be composed primarily of water ice with a considerable fraction of denser material, such as silicate rock. |
 | | Dione also forms a satellite pair with Enceladus; that is, the two moons interact gravitationally. |
| www.bartleby.com /65/di/DioneAst.html (225 words) |
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