Respuesta :
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. Eventually, white dwarfs should cool into black dwarfs, but black dwarfs are only theoretical; the universe is not old enough for the first white dwarfs to sufficiently cool and make the transition.
Larger stars find their outer layers collapsing inward until temperatures are hot enough to fuse helium into carbon. Then the pressure of fusion provides an outward thrust that expands the star several times larger than its original size, forming a red giant. The new star is far dimmer than it was as a main sequence star. Eventually, the sun will form a red giant, but don't worry — it won't happen for a while yet.
"Some five billion years from now, after the sun has become a red giant and burned the Earth to a cinder, it will eject its own beautiful nebula and then fade away as a white dwarf star," Howard Bond, of Space Telescope Science Institute in Maryland, said in a statement.
If the original star had up to 10 times the mass of the sun, it burns through its material within 100 million years and collapses into a super-dense white dwarf. More massive stars explode in a violent supernova death, spewing the heavier elements formed in their core across the galaxy. The remaining core can form a neutron star, a compact object that can come in a variety of forms.
The long lifetime of red dwarfs means that even those formed shortly after the Big Bang still exist today. Eventually, however, these low-mass bodies will burn through their hydrogen. They will grow dimmer and cooler, and eventually the lights will go out.
