Low-Mass Star (like our Sun):
* Red Giant: When a low-mass star runs out of hydrogen fuel in its core, it starts fusing hydrogen in a shell around the core. This causes the star to expand dramatically, becoming a red giant. The outer layers cool, giving the star a reddish hue.
* White Dwarf: Eventually, the red giant sheds its outer layers, forming a planetary nebula. The remaining core, composed mostly of carbon and oxygen, is incredibly dense and hot, becoming a white dwarf. White dwarfs are very small and cool over billions of years, eventually fading into black dwarfs.
Massive Star:
* Supergiant: Massive stars continue to fuse heavier elements after they run out of hydrogen. This process causes them to expand even further than red giants, becoming supergiants. They can be extremely bright and luminous.
* Supernova: When a massive star exhausts its fuel supply, its core collapses violently in a supernova explosion. This explosion releases a tremendous amount of energy, briefly outshining entire galaxies.
* Neutron Star or Black Hole: The remnants of a supernova depend on the star's initial mass. If the core is relatively small (between 1.4 and 3 solar masses), it collapses into a neutron star, an extremely dense object where protons and electrons have been squeezed together. If the core is heavier than about 3 solar masses, it collapses into a black hole, an object with such strong gravity that nothing, not even light, can escape.
