What happens to stars as they age?
It depends on mass. Once stars run out of hydrogen to fuse in there cores all hell breaks loose. In a low mass star (less than 8 solar masses) the star will expand to become a red giant, then shrink for a while to a yellow subgiant, then expand to an even bigger red giant. Then eject a lot of their material into the surrounding space, and the core will collapse and heat up – so that th ejected matter gets illuminated by a verty hot, very small star – this is a planetary nebula, and the central star is a white dwarf. The white dwarf then cools over billions of years If you want to know why all this happens – it is mostly down to loss of hydrostatic equilibrium. For more massive stars, they become red supergiants and then explode as supernovae, leaving behind a tiny neutron star or black hole. Let me know if you want me to add why all these things happen…
There are different endings to different stars. Supergiants – These stars will explode into a supernova. Depending on how big the Supergiant was and how much of the star is left creates what happens to the nova next. If its mass is low then it will become a White Dwarf and eventually a Black Dwarf. If the stars mass is higher then it will turn into a Neutron star. Eventually the Neutron star will collapse on itself and form a Black Hole. Yellow Dwarfs(Sun)- Our sun will eventually turn into a Red Giant. The Red Giant will run out of helium. The star will not be able to make oxygen or carbon dioxide. The star will then become a White Dwarf and then to a Black Dwarf. Small Stars – Most stars smaller than our sun will not have enough fusion and will sputter out and not even become a star.
