Columbia Encyclopedia

(Encyclopedia) gamma radiation, high-energy photons emitted as one of the three types of radiation resulting from natural radioactivity. It is the most energetic form of electromagnetic radiation, with a very short ...

(Encyclopedia) Lagrange, Joseph Louis, Comte zhôzĕfˈ lwē kôNt lägräNzhˈ [key], 1736–1813, French mathematician and astronomer, b. Turin, of French and Italian descent. Before the age of 20 he was professor...

(Encyclopedia) white dwarf, in astronomy, a type of star that is abnormally faint for its white-hot temperature (see mass-luminosity relation). Typically, a white dwarf star has the mass of the sun and the radius of...

(Encyclopedia) Leiden or Leyden both: līˈdən [key], city (1994 pop. 114,892), South Holland prov., W Netherlands, on the Old Rhine (Oude Rijn) River. Manufactures include medical equipment, machinery, graphic art...

(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...

(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 ...

(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 ...

(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...

(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...

(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...