Most stars are found in the main sequence area of the H-R chart. Stars spend much more of their lives burning hydrogen in their cores than they do produce energy in any other way! Sirius A, only 8.6 light-years from Earth, is the fifth closest star system known. About 90 percent of the stars in the universe, including the sun, are main-sequence stars. ...Stars start their lives as clouds of dust and gas.
Steps in the formation of a star:
Life Cycle of a Massive Star:
Step 1 - Green - A cloud of gas and dust collapses due to gravity, creating a protostar.
Step 2 - Blue - Gravitational energy powers the young star until...
Step 3 - Yellow - …nuclear fusion occurs. The main sequence star may live millions or even billions of years.
Step 4 - Red - The star expands into a red giant when the star's hydrogen level drops.
Step 5 - Orange - Different fusion processes occur. The star expands, cools, and loses mass each time.
Step 6 - White - Fusion stops and a supernova explosion occurs. Most of the star is blown away.
Step 7 - Black - Depending on the original star’s mass, either a black hole or neutron star remains.
Step 8 - Green - The material shed during the star's life joins new gas clouds, and new stars are formed