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Vulcan, in astronomy

(Encyclopedia)Vulcan, in astronomy, hypothetical planet whose existence was proposed by Le Verrier to explain part of the advance of the perihelion of Mercury, not all of which could be accounted for by gravitation...

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...

Triton , in astronomy

(Encyclopedia)Triton trītˈən [key], in astronomy, innermost and largest of the eight known moons, or natural satellites, of Neptune. ...

Titan , in astronomy

(Encyclopedia)Titan tīˈtən [key], in astronomy, the largest of the named moons, or natural satellites, of Saturn. Also known as Saturn VI (or S6), Titan is 3,200 mi (5,150 km) in diameter, orbits Saturn at a mea...

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...

X-ray astronomy

(Encyclopedia)X-ray astronomy, study of celestial objects by means of the X rays they emit, in the wavelength range from 0.01 to 10 nanometers. X-ray astronomy dates to 1949 with the discovery that the sun emits X ...

Puck, in astronomy

(Encyclopedia)Puck, in astronomy, one of the natural satellites, or moons, of Uranus. ...

Saturn, in astronomy

(Encyclopedia)CE5 Saturn and its ring system as seen from Earth Saturn, in astronomy, 6th planet from the sun. Saturn has 82 confirmed natural satellites, many of which have not been named. Five of the discov...

Regulus, in astronomy

(Encyclopedia)Regulus rĕgˈyələs [key], brightest star in the constellation Leo; Bayer designation Alpha Leonis; 1992 position R.A. 10h08m, Dec. +12°00′. A bluish-white main-sequence star of spectral class B7...

Rhea, in astronomy

(Encyclopedia)Rhea, in astronomy, one of the named moons, or natural satellites, of Saturn. Also known as Saturn V (or S5), Rhea is 950 mi (1530 km) in diameter, orbits Saturn at a mean distance of 327,487 mi (527,...