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Tethys , in astronomy

(Encyclopedia)Tethys tēˈthĭs [key], in astronomy, one of the named moons, or natural satellites, of Saturn. Also known as Saturn III (or S3), Tethys is 659 mi (1060 km) in diameter, orbits Saturn at a mean dista...

Janus, in astronomy

(Encyclopedia)Janus jāˈnəs [key], in astronomy, one of the named moons, or natural satellites, of Saturn. Also known as Saturn X (or S10), Janus is an irregularly shaped (nonspherical) body measuring about 122 m...

Dione, in astronomy

(Encyclopedia)Dione dīōˈnē [key], 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 distanc...

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...

Ceres, in astronomy

(Encyclopedia)Ceres sîrˈēz [key], in astronomy, a dwarf planet, the first asteroid to be discovered. It was found on Jan. 1, 1801, by G. Piazzi. He took three distinct observations; on the basis of these the mat...

Mars, in astronomy

(Encyclopedia)Mars, in astronomy, 4th planet from the sun, with an orbit next in order beyond that of the earth. Mars has two natural satellites, discovered by Asaph Hall in 1877. The innermost of these, Phobos...

Uranus , in astronomy

(Encyclopedia)Uranus yo͝orāˈnəs, yo͝orˈə– [key], in astronomy, 7th planet from the sun, at a mean distance of 1.78 billion mi (2.87 billion km), with an orbit lying between those of Saturn and Neptune; its...

ether, in physics and astronomy

(Encyclopedia)ether or aether, in physics and astronomy, a hypothetical medium for transmitting light and heat (radiation), filling all unoccupied space; it is also called luminiferous ether. In Newtonian physics a...