Gayle Hiscocks, age 13, of Lethbridge, Alberta, Canada, for her question.
Does a star's color really tell its temperature?
The first thing you notice is that some stars are bigger and brighter than others. Then your keen eye will notice that the stars come in slightly different colors. Sirius, the Dog Star, glitters like a brilliant white diamond. Aldebaran, the big star in Taurus the Bull, glares down like abaleful red eye. These different colors tell about the temperatures of various stars.
Almost all substances can be burned to glow as incandescent gases. Each gas burns at its own particular temperature and its burning gas glows with its own particular color. The effects of its color can be matched to certain bands on the rainbow colored spectrum. The instrument used for this celestial detective work is the spectroscope. It identifies the colors of a blazing star, and the colors tell how hot the star must be to ignite these particular substances.
The range of star temperatures is enormous, but the coolest star is not hot enough to turn the solids and liquids on earth into blazing gases. Usually, the surface is somewhere between 5,000 and 55,000 degrees Fahrenheit. It is, of course, a mixture of blazing gases, each of which must reach a particular temperature before it sheds its particular color.
This provides a simple system for classifying the various stars according to color and temperature. For example, brilliant white Sirius is an A type star. Its main ingredient is hydrogen, which gives its dazzling diamond bright light and a surface temperature of around 20,000 degrees.
Sirius is in Canis Major, the Big Dog constellation. In Canis Minor, the Little Dog, is the yellow white star Procyon. Its color indicates that its original hydrogen fuel is decreasing and its metallic elements are increasing. Procyon is classed as an F type star, with a surface temperature of around 13,500 degrees.
At the top of the constellation Orion the Hunter is the big red star Betelguese. Big Bet belongs in the M class, a group of rather young, rather cool red giant stars. Its color indicates a surface temperature of around 5,500 degrees.
Our gorgeous golden sun is an average star .in almost all respects. Its color indicates the presence of certain incandescent metals and a surface temperature of about 11,000 degrees. B type stars are blue whites with lots of helium and surface temperatures of 36,000 degrees or more. The 0 types are blue whites, hotter than 55,000 degrees.
The average star is a nuclear furnace, converting hydrogen fuel into helium and other substances at a fantastic rate. A young star contains mostly hydrogen. Its color changes as other substances are formed and ignited. Hence, the color of a star gives clues to its temperature, and sometimes the color may reveal its age.