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.
The cloud is mainly made of hydrogen. The gas is held together by its own gravity in space. If its gravitation exceeds a critical point, the cloud collapses and a star is formed. Such a star has a mass, for example, equivalent to that of our Sun. (1 solar
small star red giant large star molecular cloud
The hydrogen has been consumed, and the star expands. Such a giant is around 1,500 times as big as our Sun— and 100,000 times brighter. The dying star opens its shell— from which gas and plasma spread like mist. It’s a process that gives rise to heavy ele
red supergiant white dwarf neutron star black hole supernova planetary nebula