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corona, in astronomy

(Encyclopedia)corona, luminous envelope surrounding the sun, outside the chromosphere. Its density is less than one billionth that of the earth's atmosphere. The corona is visible only at the time of totality durin...

perturbation

(Encyclopedia)perturbation pŭrˌtərbāˈshən [key], in astronomy and physics, small force or other influence that modifies the otherwise simple motion of some object. The term is also used for the effect produce...

Sierra Madre, mountain system, Mexico

(Encyclopedia)Sierra Madre dĕl so͝orˈ [key] is a tumbled, broken mass of uptilted mountains that touch the Pacific coast but form into no clearly defined range. It spreads over S Mexico between the volcanic belt...

transit

(Encyclopedia)transit, in astronomy, passage of a body across a meridian or passage of a small body across the visible disk of a larger one. (The passage of a large body across a smaller one is called an eclipse or...

Chamberlin, Thomas Chrowder

(Encyclopedia)Chamberlin, Thomas Chrowder, 1843–1928, American geologist, b. Mattoon, Ill., grad. Beloit College, 1866. He was professor of geology at Beloit (1873–82), president of the Univ. of Wisconsin (1887...

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 ...

time , sequential arrangement of all events

(Encyclopedia)time, sequential arrangement of all events, or the interval between two events in such a sequence. The concept of time may be discussed on several different levels: physical, psychological, philosophi...

dwarf planet

(Encyclopedia)dwarf planet, a nonluminous body of rock or gas that orbits the sun and has a rounded shape due to its gravity. Unlike a planet, a dwarf planet is not capable of clearing its orbit of smaller objects ...

comet

(Encyclopedia)CE5 Comet: Whatever the direction of a comet's flight, its “tail” always points away from the sun. The tail disappears when the comet is far from the sun. comet [Gr.,=longhaired], a small cele...

space probe

(Encyclopedia)space probe, space vehicle carrying sophisticated instrumentation but no crew, designed to explore various aspects of the solar system (see space exploration). Unlike an artificial satellite, which is...