Eventually, a main sequence star burns through the hydrogen in its core, reaching the end of its life cycle. At this point, it leaves the main sequence. Stars smaller than a quarter the mass of the sun collapse directly into white dwarfs. White dwarfs no longer burn fusion at their center, but they still radiate heat.
Neutron stars are created when giant stars die in supernovas and their cores collapse, with the protons and electrons essentially melting into each other to form neutrons. Credit: NASA/Dana Berry Neutron stars are city-size stellar objects with a mass about 1.4 times that of the sun.
Scientists think that 20 out of the 30 stars nearest to Earth are red dwarfs; however, none of them can be seen with the naked eye. The closest star to the sun, Proxima Centauri, is a red dwarf. Despite its frequent appearance, the term "red dwarf" does not refer to a single kind of star.
Supergiant stars are the largest stars in the universe. They can be thousands of times bigger than our Sun and have a mass up to 100 times greater. The largest known supergiant star, VY Canis Majoris, is up to 2,100 times the size of the Sun (based on upper estimates).
White Dwarf Stars A white dwarf is what stars like the Sun become after they have exhausted their nuclear fuel. Near the end of its nuclear burning stage, this type of star expels most of its outer material, creating a planetary nebula. Only the hot core of the star remains.