Lie on a blanket or a reclining lawn chair and let your eyes dance around the celestial theater. One of the first things you'll notice is that there's a wide variety in the brightness of stars. The brightness, or magnitude, of a star depends on two things, the star's distance and how powerful it is. Not all stars are the same size. Our star the sun is less than a million miles in diameter, but some stars can be hundreds of millions of miles wide.
Every single star is a giant nuclear furnace.
Nuclear fusion, a very complicated process, is what makes our sun and the rest of the stars shine. Hydrogen atoms are fused together to form heavier helium atoms deep inside a star. But not all the hydrogen is turned into helium. A tiny amount of the hydrogen is converted into tremendous amounts of energy that surge out of the star. The sun is the closest star to the Earth, only about 93 million miles away.