A star is a huge mass of plasma-state material in space that radiates energy, usually in the form of electromagnetic radiation. Stars generate this energy by thermonuclear fusion, which is where two atomic nuclei are fused together to produce a new nucleus. Energy is released by this process, which is radiated outward into space. The energy created by our sun takes 8.3 light-minutes to reach the Earth. The principle fuel for this fusion process is hydrogen and helium. The end product usually stops around the element oxygen because the nuclei get too large to keep fusing together. Stars may range from blue stars, which are young, in their beginning stages, to yellow, such as our sun, in mid-life. When they have used nearly all their fuel, they may swell to become red giants, many times the size they previously occupied. Upon near-death, they may become red dwarfs or white dwarfs. Black holes are also the remains of left-over star material that has become so compact and dense, not even light can escape its gravitational attraction.