Scopin'USA - Stars Stars Stars are huge spheres of mainly hydrogen gas.
Starlight comes from nuclear fusion produced in their cores.
The sun is about average physically, larger stars live short lives, smaller stars live longer. Stars are born out of huge but tenuous clouds of hydrogen gas and dust. As areas of these clouds shrink into local densities the gas becomes dense enough for hydrogen to fuse into helium. Multiple star systems are more common than single-star systems. These physical properties change with time.