Labels:text | screenshot | fruit | apple OCR: MAIN-SEQUENCE STARS Outer layers IN THE CORE OF A main-sequence star, of hydrogen nuclear reactions fuse hydrogen to Core of form helium. Stars spend most of hydrogen their lives in this stable state. When fusing to these reactions cease, the helium core form helium contracts, heating the surrounding shell of hydrogen gas until fusion starts in this shell. The energy radiated by this new reaction applies pressure to the star's outer layers, which expand and cool. The star then evolves into a red giant or a supergiant, depending A STAR IN ITS PRIME on its initial mass. When their properties are plotted on a Hertzsprung-Russell diagram, about 90 percent of stars fall into a band on the diagram called the Main Sequence. NUCLEAR SELECTED FACT FUSION STARS FILE
