A blackbody (sometimes spelled "black body") is a theoretically ideal radiator and absorber of energy at all electromagnetic wavelength s. The term comes from the fact that a cold blackbody appears visually black.
The energy emitted by a blackbody is called blackbody radiation. This takes the form of an electromagnetic field having an intensity-versus-wavelength relation whose graph looks like a skewed, bell-shaped statistical curve. The maximum point on the curve shows the wavelength at which the radiation intensity is greatest. This wavelength depends on the thermodynamic temperature , in kelvin s, of the object. The higher the temperature, the shorter the wavelength at which the radiation is most intense. The wavelength and temperature are related by a function involving Wien's constant .
Scientists attempt to determine the temperatures of distant objects in space by observing their blackbody radiation. The calculations are made by assuming that celestial objects behave as perfect blackbodies. A blackbody is a theoretical ideal, but many astronomical objects come reasonably close to this ideal.