They are found singily, in pairs, and in clusters of dozens, hundreds, thousands, and millions of stars.
Stars are truly a many varied beast, but all stars share one thing in common.
What makes a star a star, and not a planet or brown dwarf, is that the temperature and density of its core is high enough for nuclear fusion to occur. The next time you're basking in the sunlight of our own star, the Sun, consider the fact that every second 650 billion kilograms of hydrogen is being fused into helium in its core. The Sun's hydrogen fuel, however, won't last forever. Some of the links on this page are sites not located at the United States Air Force Academy.