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solar energy

(Encyclopedia)solar energy, any form of energy radiated by the sun, including light, radio waves, and X rays, although the term usually refers to the visible light of the sun. Solar energy is needed by green plants...

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...

Menzel, Donald Howard

(Encyclopedia)Menzel, Donald Howard, 1901–76, American astrophysicist, b. Florence, Colo. From 1926 to 1932 he was with the Lick Observatory in Calif. In 1932 he joined the faculty at Harvard, where he became pro...

quadrature

(Encyclopedia)quadrature, in astronomy, arrangement of two celestial bodies at right angles to each other as viewed from a reference point. If the reference point is the earth and the sun is one of the bodies, a pl...

Scholz's star

(Encyclopedia)Scholz's star, dim binary star system, consisting of a red dwarf and brown dwarf, in the constellation Monoceros, apparent magnitude 18.3. The red dwarf is a tiny star, with less than ten percent the ...

Glen Roy

(Encyclopedia)Glen Roy, valley, Highland, W Scotland, E of Loch Lochy. The Parallel Roads, three terraces on each side of the valley at corresponding heights, are believed to mark receding levels of a lake that onc...

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...

precession of the equinoxes

(Encyclopedia)CE5 Precession of the equinoxes (the points at which the earth's celestial equator intersects its ecliptic) is due to the slow rotation of the earth's axis around a perpendicular to the ecliptic. ...

Marquis, Don

(Encyclopedia)Marquis, Don (Donald Robert Perry Marquis) märˈkwĭs [key], 1878–1937, American author, b. Walnut, Ill. In 1912 he began the humorous column “The Sun Dial” in the New York Sun and later conduc...

sextant

(Encyclopedia)CE5 Sextant sextant, instrument for measuring the altitude of the sun or another celestial body; such measurements can then be used to determine the observer's geographical position or for other n...