article_snippet.sent: When a star runs out of fuel a star usually collapses in on a star.
article_snippet.sent: Stars more than eight times the mass of our sun will explode in a supernova, leaving behind a neutron star or black hole.
article_snippet.sent: Smaller stars, though, will shed Smaller stars outer layers and leave behind a hot dense core – known as a white dwarf.
article_snippet.sent: A white dwarf contains a similar amount of mass to A white dwarf but will be much smaller – about the size of Earth – making gravity at A white dwarf surface much more intense.
article_snippet.sent: They are thought to be able to burn for tens or hundreds of billions of years - at which point They  become black dwarfs –
article_snippet.sent: but as the universe is not this old, no black dwarfs exist in the universe yet.
article_snippet.sent: Unlike stars like our sun, collapsed dead stars that belong to stellar pairs, or binaries, can siphon matter from dead stars that belong to stellar pairs companions.
article_snippet.sent: But it is the potential for these to be white dwarf stars that is the most intriguing theory.
article_snippet.sent: There are already known to be many young, massive stars orbiting our galaxy's central supermassive black hole - but why there would be thousands of white dwarf stars as well is not clear.
article_snippet.sent: White dwarfs are what are left when medium-mass stars - including our sun - shed White dwarfs outer layers at the end of White dwarfs life.
article_snippet.sent: Behind is left the hot, dense core which burns white.
article_snippet.sent: If the white dwarf gathers too much material from a companion, the white dwarf mass will reach a critical point and the star will explode.