The hydrogen gas is usually the first type of gas consumed in a star and then other gas elements such as carbon, Oxygen, and helium are consumed. This chain reaction fuels the star for millions or billions of years depending upon the amount of gases there are. The star manages to avoid collapsing at this point because of the equilibrium achieved by itself. The gravitational pull from the core of the star is equal to the gravitational pull of the gases forming a type of orbit, however when this equality is broken the star can go into several different stages. Usually if the star is small in mass, most of the gases will be consumed while some of it escapes. This occurs because there is not a tremendous gravitational pull upon those gases and therefore the star weakens and becomes smaller. It is then referred to as a white dwarf. A teaspoonful of white dwarf material would weigh five-and-a-half tons on Earth. Yet a white dwarf star can contract no further; it's electrons resist further compression by exerting an outward pressure that counteracts gravity. If the star was to have a larger mass, then it might go supernova, such as SN 1987A, meaning that the nuclear fusion within the star simply goes out of control, causing the star to explode. After exploding, a fraction of the star is usually left (if it has not turned into pure gas) and that fraction of the star is known as a neutron star. Neutron stars are so dense, a teaspoonful would weigh 100 million tons on Earth. As heavy as neutron stars are, they too can only contract so far. This is because, as crushed as they are, the neutrons also resist the inward pull of gravity, just as a white dwarf's electrons do. A black hole is one of the last options that a star may take. If the core of the star is so massive (approximately 6-8 times the mass of the sun) then it is most likely that when the star's gases are almost consumed those gases will collapse inward, forced into the core by the gravitational force laid upon them.
