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Epimetheus, in astronomy

(Encyclopedia)Epimetheus, in astronomy, one of the named moons, or natural satellites, of Saturn. Also known as Saturn XI (or S11), Epimetheus is an irregularly shaped (nonspherical) body measuring about 89 mi (144...

Eris, in astronomy

(Encyclopedia)Eris, in astronomy, the largest known dwarf planet. Eris, whose highly eccentric elliptical orbit ranges from 38 AU to 97 AU and is inclined more than 44°, is the largest known object of the Kuiper b...

Eros, in astronomy

(Encyclopedia)Eros, in astronomy: see asteroid. ...

Hyperion, in astronomy

(Encyclopedia)Hyperion hīpērˈēən [key], in astronomy, one of the named moons, or natural satellites, of Saturn. Also known as Saturn VII (or S7), Hyperion is the largest highly irregular (nonspherical) body in...

Iapetus, in astronomy

(Encyclopedia)Iapetus īăpˈĭtəs [key], in astronomy, one of the named moons, or natural satellites, of Saturn. Also known as Saturn VIII (or S8), Iapetus is 907 mi (1460 km) in diameter, orbits Saturn at a mean...

Icarus, in astronomy

(Encyclopedia)Icarus, in astronomy: see asteroid. ...

Hyades, in astronomy

(Encyclopedia)Hyades hīˈədēz [key], in astronomy, open star cluster in the constellation Taurus, located immediately to the right of the bright star Aldebaran. The cluster is about 130 light-years from the eart...

Hydra, in astronomy

(Encyclopedia)Hydra, in astronomy, southern constellation lying S of Corvus, Crater, Virgo, Leo, and Cancer. It is a long, slender, winding constellation traditionally depicted as a snake and known also as the Wate...

Io, in astronomy

(Encyclopedia)Io īˈō [key], in astronomy, one of the 39 known moons, or natural satellites, of Jupiter. Io is subject to Jupiter's enormous tidal forces and is, as a result, the most volcanically active body in ...

Juno, in astronomy

(Encyclopedia)Juno jo͞oˈnō [key], in astronomy, 3d asteroid to be discovered. It was found in 1804 by C. Harding. It has a diameter of c.120 mi (190 km). Its average distance from the sun is 2.67 astronomical un...