THE EVOLUTION OF STARS
»The life of a sun often lasts for billions of years— and yet each has a very specific expiration date. This can be precisely calculated by looking at the amount of nuclear energy reserves it has (mainly hydrogen and helium). Once this fuel has been used up, an unstoppable process of disintegration begins— the star dies. But the fate of the star after its death depends on how massive it was during its lifetime. A star that has a residual 1.44 solar mass (around 3.2 octillion tons) becomes a blindingly bright white dwarf. On the other hand, a dying star of 1.44 to 3 solar masses ends in a big bang— a supernova. After that it ekes out an existence for many millions of years as a neutron star— an extremely dense sphere with a diameter of 12 miles. The end is different for giant stars with more than 3 solar masses. They also explode, but they subsequently mutate into black holes. Experts predict that our Sun’s hydrogen reserves will last about 5 to 6 billion more years at most.
small star red giant large star molecular cloud
red supergiant white dwarf neutron star black hole supernova planetary nebula