If a star is too small to become a neutron star or simply explode into a supernova, it will eventually evolve into a white dwarf – an extremely dense and dull star which has expended all of its fuel and is no longer experiencing nuclear fission at its core. Often no larger then the Earth, white dwarves slowly cool via the emission of electromagnetic radiation. Over ridiculously long periods of time, white dwarves eventually cool enough to stop emitting light and heat altogether – thereby becoming what is known as a black dwarf, almost invisible to the observer. Black dwarf-hood marks the end of stellar evolution for many stars. It’s believed that no black dwarves currently exist in the universe, as it takes so long for them to form. Our sun will degenerate into one in around 14.5 billion years.