luminosity definition of luminosity in the Free Online Encyclopedia.

luminosity, in astronomy, the rate at which energy of all types is radiated by an object in all directions. A star's luminosity depends on its size and its temperature, varying as the square of the radius and the fourth power of the absolute surface temperature. The sun is a medium-sized star with a luminosity of 3.8×10³³ ergs per sec. The luminosities of other stars are commonly expressed in terms of the sun's luminosity. The known luminosities of stable stars range from about 1/1,000,000 that of the sun for a relatively cool white dwarf 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 the earth but does not emit enough light or other radiation to be
..... Click the link for more information. to about 1,000,000 times that of the sun for the hottest known supergiant star. See magnitude 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 scale such that the brightest stars were of 1st magnitude and the
..... Click the link for more information. ; mass-luminosity relation mass-luminosity relation, in astronomy, law stating that the luminosity of a star is proportional to some power of the mass of the star. More massive stars are in general more luminous.
..... Click the link for more information. ; stellar evolution stellar evolution, life history of a star , beginning with its condensation out of the interstellar gas (see interstellar matter ) and ending, sometimes catastrophically, when the star has exhausted its nuclear fuel or can no longer adjust itself to a stable
..... Click the link for more information. .

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luminosity