Time Frame

• The sun has endured for about 4.6 billion years and has about 5 billion years of life left. The smaller stars, with very low mass, may burn for 15 billion years or more. Larger stars with very high mass burn out very quickly, sometimes in just a few million years.
  
  

Features

• Each star begins its life as a nebula, which is a diffused cloud of interstallar gas and dust. As time passes, the cloud collapses, creating a protostar. Then the star begins to shine, becoming a main sequence star. Stars remain in the main sequence phase for the majority of their life cycle. At the core of the star, hydrogen is converted to helium through nuclear fusion. When the available hydrogen starts to run out, the star contracts. Then it begins to expand again. Most stars become a red giant at this stage. Low mass stars shrink into white dwarfs, then cool and become black or brown dwarf stars. Massive stars, on the other hand, go supernova.
  
  

Function

• The life span of a star depends on its mass. This is because more massive stars burn at much higher temperatures, using their available fuel at a faster rate. Stars with low mass are very efficient in the way that they burn their nuclear fuel, and thus live much longer.
  
  

Benefits

• The mass of the sun has given it longevity. It's also provided it with the ability to produce sufficient heat and light for life to evolve and thrive on Earth. If it were more massive, it would have died young. If it were less massive, its lifespan would have been longer, but it would have left the Earth too cold to support life.
  
  

Effects

• A moderately massive star, with a mass of 1.4 times that of the sun, will become a neutron star as a result of a supernova. More massive stars whose mass is 3 times or greater than the sun will become a black hole after becoming a supernova. If the star is 5 or more times massive than the sun, heavier fusion reactions take place before the star finally burns out. When all elements within the core but iron have been exhausted, the star explodes into supernova. These stars may also become neutron stars or black holes. In some cases, it may become a pulsar.