HEAT & THERMODYNAMICS A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z                    HOME ABOUT CATEGORIES SITE MAP COPYRIGHT ADVERTISE CONTACT entire Web this site blackbody Approximation to a blackbody. Image credit: NASA Variation in blackbody curves with temperature. Image credit: ESA A theoretical object that is both a perfect absorber and a perfect radiator of electromagnetic radiation. A blackbody absorbs all the radiation that falls on it, converts it into internal energy (heat), and then re-radiates this energy into the surroundings. The re-radiated thermal energy, known as blackbody radiation, has a continuous spectrum governed solely by the body’s temperature. For any given temperature, there is a specific wavelength at which radiation emission is greatest. The effective temperature (Te), or blackbody temperature, is the surface temperature that a star, or other object, would have if it were a blackbody that radiated the same amount of energy per unit area. This is a useful and widely employed measure of stellar surface temperature. Te can be calculated from the Stefan-Boltzmann law, which states that the total energy radiated by a blackbody varies as the fourth power of its absolute temperature. This law leads to the formula: L = 4σR2Te4 where L is the luminosity of the body, R is its radius, and σ (= 5.67 × 10-8 W/m2/K4) is the Stefan-Boltzmann constant. Substituting solar values for L and R gives a value for the effective temperature of the Sun of about 5,780 K. Related category    • HEAT AND THERMODYNAMICS Also on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History Transport Concepts & Designs (partner site) BACK TO TOP