Star Temperatures

Blackbodies are objects that absorb all radiation falling on them. They then re-emit that radiation in a very specific range of wavelengths. Wien's Law states that the wavelength of the radiation emitted depends on the blackbody's temperature. You may have noticed, for example, that coals in a fire change colors as they become hotter or cooler. Blackbody emitters such as stars will be different colors depending on their temperatures. This is because those with higher temperatures emit more of their radiation at shorter wavelengths (higher frequencies). Thus, the hottest stars are bluish-white, while the coolest stars are red. You can explore this relationship of temperature to energy emitted at a given wavelength by changing the temperature in the temperature box below the graph. Astronomers use this relationship between wavelength and temperature to estimate the temperature of the sun and stars.