Luminosity

Basic property used to characterize stars, luminosity is defined as the total energy radiated by a starSelf-luminous object held together by its own self-gravity. Often refers to those objects which generate energy from nuclear reactions occurring at their cores, but may also be applied to stellar remnants such as neutron stars. each second. An object’s luminosity is often compared to that of the SunOur parent star. The structure of Sun's interior is the result of the hydrostatic equilibrium between gravity and the pressure of the gas. The interior consists of three shells: the core, radiative region, and convective region. Image source: http://eclipse99.nasa.gov/pages/SunActiv.html. The core is the hot, dense central region in which the (L_sun = 4 × 1033 ergs/s = 3.9 × 10²⁶ Watts). Luminosity has the same units as power (energy per second). Luminosity can be related to the absolute magnitudeMagnitude an object would have if placed at a distance of exactly 10 parsecs (= 32.6 light years). A supergiant star might have an absolute magnitude of -8 whereas a dim red dwarf might have an absolute magnitude of +16. The Sun has an absolute magnitude of +4.8 – about, M_V, by the equation:

Where, L* is the luminosity of the object in question and L_std is a reference luminosity (often the luminosity of a ‘standard’ star such as Vega). Luminosity can be quoted for the energy emitted within a finite waveband (e.g. optical luminosity), or for the energy emitted across the whole electromagnetic spectrum (“bolometric” luminosity). Note that measurement of the luminosity requires an object’s apparent magnitude and the distance to the object. Thus, estimates of luminosity rely on accurate distance measurements.