Colors of the stars

One star may have a spectrum that is like that of other stars. The stars in each spectral class are found to have the same color. The colors range from blue to red. Our sun is a yellow star, in the middle of the range. The temperature of a star can also be found by measuring colors in the spectrum. The blue stars are large, hot, and brilliant, with temperatures of 25,000 degrees or more. Red stars are rather cool and have surface temperatures of 1,600 degrees or less. To find what chemical elements are in the stars, the astronomer compares their spectra with spectra made in the laboratory. All the elements found in the stars are also present in the earth, but the stars are basically balls of very hot gas, mainly hydrogen and helium. The astronomers also use special types of telescopes which can photograph large areas of sky. Still another type of instrument is the radio telescope. This has a very large antenna, a receiver, and a registering meter.