(1998).ISO/media/astdict/b/graphics/bbody.jpg)
Black body radiation. The distribution with wavelength of the radiation emitted by black
bodies at 12,000, 6,000 and 3,000 K. These are typical surface temperatures for stars.
The shape of the curves illustrates the colour and luminosity differences between cool
and hot stars.
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The radiation emitted by a black body. The intensity of radiation as a function of
wavelength depends only on the temperature of the body. The graph showing the
distribution of intensity with wavelength is often called the Planck curve after
the physicist Max Planck, who formulated the relationship. The Planck curves are
hill-shaped, with a distinct peak (see illustration). The wavelength of the peak
decreases with increasing temperature of the black body in such a way that the
product of peak wavelength and absolute temperature is constant. The total amount
of energy emitted by a black body is proportional to the product of its surface
area and the fourth power of its temperature (T4).
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