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Mercury, in astronomy

(Encyclopedia)Mercury, in astronomy, nearest planet to the sun, at a mean distance of 36 million mi (58 million km); its period of revolution is 88 days. Mercury passes through phases similar to those of the moon a...

Atlas, in astronomy

(Encyclopedia)Atlas, in astronomy, one of the named moons, or natural satellites, of Saturn. Also known as Saturn XV (or S15), Atlas is a small, irregularly shaped (nonspherical) body measuring about 25 mi (40 km) ...

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...

Aquila, in astronomy

(Encyclopedia)Aquila [Lat.,=the eagle], equatorial constellation located N of Sagittarius and Capricornus, lying partly in the Milky Way. It is sometimes depicted as an eagle. It contains the bright star Altair (Al...

Hercules, in astronomy

(Encyclopedia)Hercules hûrˈkyəlēzˌ [key], in astronomy, northern constellation located between Lyra and Corona Borealis. It is traditionally depicted as the hero Hercules in a kneeling position. There are no v...

Hermes, in astronomy

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

Hidalgo, in astronomy

(Encyclopedia)Hidalgo hĭdălˈgō [key], in astronomy: see asteroid. ...

Hadar, in astronomy

(Encyclopedia)Hadar or Beta Centauri bāˈtə sĕntôrˈē [key], bright star in the constellation Centaurus; 1992 position R.A. 14h01.7m, dec. −60°13′. A bluish-white giant of spectral class B1 II, it has an ...

Andromeda, in astronomy

(Encyclopedia)Andromeda, in astronomy, northern constellation located to the NE of Pegasus and to the S of Cassiopeia. Its brightest star, Alpheratz (Alpha Andromedae), marks the northeast corner of the Great Squar...

Ganymede, in astronomy

(Encyclopedia)Ganymede gănˈēmēdˌ [key], in astronomy, one of the moons, or natural satellites, of Jupiter; the largest natural satellite in the solar system, it is larger than the planet Mercury. ...