A star's color provides a direct measurement of its surface temperature; the hottest stars shine blue-white, while the coolest are dull orange or red. In turn, the temperature indicates how much energy a given area of the star's surface radiates into space every second. When that is multiplied by the star's total surface area, it tells us the star's luminosity -- a measurement of how much energy it radiates into space every second.
The Sun is a typical middle-aged, intermediate-mass main-sequence star.
1. Core. The star's nuclear "furnace," where fusion reactions combine hydrogen atoms to produce helium, yielding energy in the process.
This document was last modified: October 19 2009.
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