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parsec
(Encyclopedia)parsec pärˈsĕc [key] [parallax + second], in astronomy, basic unit of length for measuring interstellar and intergalactic distances, equal to 206,265 times the distance from the earth to the su...nutation
(Encyclopedia)nutation, in astronomy, a slight wobbling motion of the earth's axis. The causes of nutation are similar to those of the precession of the equinoxes, involving the varying attraction of the moon on th...Ritchey, George Willis
(Encyclopedia)Ritchey, George Willis, 1864–1945, American astronomer, b. Meigs co., Ohio, studied at the Univ. of Cincinnati (1883–84, 1886–87). He was superintendent of instrument construction (1899–1904) ...zenith
(Encyclopedia)zenith, in astronomy, the point in the sky directly overhead; more precisely, it is the point at which the celestial sphere is intersected by an upward extension of a plumb line from the observer's lo...Celsius, Anders
(Encyclopedia)Celsius, Anders änˈdərs sĕlˈsēŭs [key], 1701–44, Swedish astronomer. While professor of astronomy at the Univ. of Uppsala (1730–44), he traveled through Germany, France, and Italy, visiting...pigeon
(Encyclopedia)pigeon, common name for members of the large family Columbidae, land birds, cosmopolitan in temperate and tropical regions, characterized by stout bodies, short necks, small heads, and thick, heavy pl...atlas, in geography
(Encyclopedia)atlas, in geography, collection of maps or charts. It usually includes data on various features of a country, e.g., its topography, natural resources, climate, and population, as well as its agricultu...Chaldaea
(Encyclopedia)Chaldaea or Chaldea both: kăldēˈə [key], properly the southernmost portion of the valley of the Tigris and the Euphrates rivers. Sometimes it is extended to include Babylonia and thus comprises al...opposition
(Encyclopedia)opposition, in astronomy, alignment of two celestial bodies on opposite sides of the sky as viewed from earth. Opposition of the moon or planets is often determined in reference to the sun. Only the s...color index
(Encyclopedia)color index, in astronomy, difference in an object's brightness as recorded between any two well-defined bands of the electromagnetic spectrum by using optical filters of different colors. If blue and...Browse by Subject
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