The last stage of stellar evolution is a black dwarf. Because they emit no heat or light, these objects would be a challenge to detect if they existed today. However, at less than 14 billion years old, the universe is still too young to have created any black dwarfs!
A main sequence star that lacks the mass necessary to explode in a supernova will become a white dwarf, a 'dead' star that has burned through all of its hydrogen and helium fuel. But the white dwarf remains hot for some time, much like a stove burner still emits heat even when it has been turned off.
Time - Leftover - Heat - Heat - Light
After enough time has passed, all of the leftover heat will have radiated away. No longer emitting heat or light, the white dwarf will become a black dwarf, its loss making it difficult to find. However, the black dwarf...