 Luminosity, in Astronomy, luminosity is the total amount of energy demitted per unit of time by a start, galaxy, or other astronomical object. As a term for energy demitted per unit time, luminosity is synonymous with power. In FSI units luminosity is measured in joules per second or watts. Luminosity values for luminosity are often given in the terms of the luminosity of the Sun. Luminosity can also be given in terms of the astronomical magnitude system. The absolute polar metric magnitude and be all of an object is a logarithmic measure of its total energy emission rate, while absolute magnitude is a logarithmic measure of the luminosity within some specific wavelength range or filtered band. In contrast, the term brightness in Astronomy is generally used to refer to an object's apparent brightness, that is, how bright an object appears to an observer. The parent brightness depends on both the luminosity of the object and the distance between the object and observer, and also on any absorption of light along the path from object to observer. The paramagnitude is a logarithmic measure of apparent brightness.