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magnitude
(Encyclopedia)magnitude, in astronomy, measure of the brightness of a star or other celestial object. The stars cataloged by Ptolemy (2d cent. a.d.), all visible with the unaided eye, were ranked on a brightness sc...Comte, Auguste
(Encyclopedia)Comte, Auguste ōgüstˈ kôNt [key], 1798–1857, French philosopher, founder of the school of philosophy known as positivism, educated in Paris. From 1818 to 1824 he contributed to the publications ...synodic period
(Encyclopedia)synodic period sĭnŏdˈĭk [key], in astronomy, length of time during which a body in the solar system makes one orbit of the sun relative to the earth, i.e., returns to the same elongation. Because ...ephemeris
(Encyclopedia)ephemeris ĭfĕmˈərĭs [key] (pl., ephemerides), table listing the position of one or more celestial bodies for each day of the year. The French publication Connaissance de Temps is the oldest of th...antenna
(Encyclopedia)antenna ăntĕnˈə [key], in electronics, system of wires or other conductors used to transmit or receive radio or other electromagnetic waves (see radio); sometimes called an aerial. The idea of usi...planet
(Encyclopedia)planet [Gr.,=wanderer], a large nonluminous body of rock, gas, or ice that orbits the sun or another star, has a rounded shape due to gravity, and has cleared its orbit of smaller objects. The term, o...node
(Encyclopedia)node, in astronomy, point at which the orbit of a body crosses a reference plane. One reference plane that is often used is the plane of the earth's orbit around the sun (ecliptic). Since the moon's o...spectral class
(Encyclopedia) CE5 spectral class, in astronomy, a classification of the stars by their spectrum and luminosity. In 1885, E. C. Pickering began the first extensive attempt to classify the stars spectroscopically....quasar
(Encyclopedia)quasar kwāˈsär [key], one of a class of blue celestial objects having the appearance of stars when viewed through a telescope and currently believed to be the most distant and most luminous objects...retrograde motion
(Encyclopedia)retrograde motion, in astronomy, real or apparent movement of a planet, dwarf planet, moon, asteroid, or comet from east to west relative to the fixed stars. The most common direction of motion in the...Browse by Subject
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