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Genzel, Reinhard

(Encyclopedia)Genzel, Reinhard, 1952–, German astrophysicist, Ph.D. Univ. of Bonn, 1978. He was on the faculty at the Univ. of California, Berkeley, from 1980 to 1986, when he left to become director at the Max P...

Queloz, Didier Patrick

(Encyclopedia)Queloz, Didier Patrick, 1966–, Swiss astronomer, Ph.D. Univ. of Geneva, 1995. He has been a member of the faculty at the Univ. of Geneva since 2003 (professor from 2008) and since 2013 also has been...

year

(Encyclopedia)year, time required for the earth to complete one orbit about the sun. The solar or tropical year is measured relative to the sun and is equal to 365 days, 5 hr, 48 min, 46 sec of mean solar time (see...

sidereal time

(Encyclopedia)sidereal time (ST), time measured relative to the fixed stars; thus, the sidereal day is the period during which the earth completes one rotation on its axis so that some chosen star appears twice on ...

cycle

(Encyclopedia)cycle, in astronomy, period of time required for the recurrence of some celestial event. The length of a cycle may be measured relative to the sun or to the fixed stars (see sidereal time). A frequent...

muon

(Encyclopedia)muon myo͞oˈŏn [key], elementary particle heavier than an electron but lighter than other particles having nonzero rest mass. The name muon is derived from mu meson, the former name of the particle....

planetary system

(Encyclopedia)planetary system, a star and all the celestial bodies bound to it by gravity, especially planets and their natural satellites. Until the last decade of the 20th cent., the only planetary system known ...

Hipparchus, Greek astronomer

(Encyclopedia)Hipparchus, fl. 2d cent. b.c., Greek astronomer, b. Nicaea, Bithynia. He is the first systematic astronomer of whom there are records. He made his observations chiefly on the island of Rhodes. Ptolemy...

Calypso, in astronomy

(Encyclopedia)Calypso, in astronomy, one of the named moons, or natural satellites, of Saturn. Also known as Saturn XIV (or S14), Calypso is a small, irregularly shaped (nonspherical) body measuring about 21 mi (34...

Spica

(Encyclopedia)Spica spīˈkə [key], brightest star in the constellation Virgo; Bayer designation Alpha Virginis; 1992 position R.A. 13h24.8m, Dec. −11°07′. A bluish-white star of spectral class B1 V, its appa...