Blackbody

Blackbody: An object whose radiative properties depend only on its temperature. If an object (star, planet, galaxy) behaves like a blackbody, then its radiation is said to be thermal, and, depending on its temperature, its spectrum has a very characteristic shape and intensity (given by Planck's function).

For more details, see the Wiki Encyclopedia page at: http://en.wikipedia.org/wiki/Planck's_law_of_black_body_radiation

Wien's Law: The wavelength of the maximum brightness (intensity) is inversely proportional to temperature. The spectrum of a hot object peaks at shorter wavelengths than does the spectrum of a cool object.

Note also that a hotter object radiates more (is more luminous) than a cooler one at all wavelengths.