Heat & Temperature

Color Temperatures

A very hot object, such as the filament of a light bulb, glows with a color that depends on its temperature. Long before thermometers came into use, people used color to judge the temperature of an object. The traditional instructions for making a samurai sword, for instance, call for quenching the sword when it glows with the color of the morning sun. Today astronomers use color to estimate the temperature of stars. Very hot stars appear blue-white and the coolest star look reddish. Our own star, the sun, is a yellow-white star somewhere in between these two extremes, with a temperature of about 6,000 K (5,700 C ).