The Sun is the Solar System's star, and by far its chief component. Its large mass (332,900 Earth masses) produces temperatures and densities in its core great enough to sustain nuclear fusion, which releases enormous amounts of energy, mostly radiated into space as electromagnetic radiation, peaking in the 400--to--700 nm band we call visible light. It is believed that the Sun's position on the main sequence puts it in the "prime of life" for a star, in that it has not yet exhausted its store of hydrogen for nuclear fusion. The Sun is a population I star; it was born in the later stages of the universe's evolution, and thus contains more elements heavier than hydrogen and helium ("metals" in astronomical parlance) than older population II stars.