We can tell how hot something is by its color. A blue star like Rigel has a surface temperature of about 50,000° Fahrenheit. A red star like Betelgeuse (at the other end of the rainbow spectrum) has a temperature of about 5,000° Fahrenheit. Our star, Sol, which is yellow, has a surface temperature in between the others. It is about 10,000° Fahrenheit, which is the same as 5500° Centigrade.
It is harder to tell what the temperature in the center of the sun is. We have designed mathematical models of the sun which predict that the core temperature is 27,000,000°F. There is a LOT of energy being produced by the sun.
(published on 10/22/2007)