Abstract (summar of paper)
When observing a star, the lager it is the shorter its life is going to be. The smaller it is the longer the life. Shorter life is not saying much though, as the most massive stars live for billions of years. When a star reaches about middle age, it starts fusing hydrogen into helium. Once it has run out of usable hydrogen that it can convert into helium, it can then take on one of several paths. It can lead to white dwarfs, novae, supernovae, neutron stars or even black holes.
II. When a star begins the phase of dying, it is deprived of the energy that is needed to prevent it from collapsing in on its core. The size of the star depends on what happens next in this vicious cycle.
III. We still don’t know exactly what happens to low mass stars when they die as the universe has not been around long enough for a low mass star to stop fusing hydrogen into helum. It is believed that a star with a solar mass of less than 0.5 will never be able to fuse helum even after the core stops hydrogen fusion. The star is not massive enough to exert pressure on its core. These are called red dwarfs. An example of a red dwarf is Proxima Centauri, which is shown below.
Red dwarfs with a mass of less than 0.1 scientist believe will stay on the main sequence for over 6 trillion years before they start to die. Lower mass stars are thought to be very convective which means these stars will not have the outer layers of hydrogen. If the star does have these hydrogen layers, then it is more likely to be a mid sized star that will form into a red giant.
IV. In mid size solar mass stars, hydrogen that was fusing in the core is still fusing outside the core into a shell. The much hotter core, starts to push out the layers of the star, and causes them to expand and cool and turns the star into a red giant. As the...