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[[Image:White dwarf stars browse.jpg|thumb|White Dwarf Stars photographed by the Hubble Space Telescope.]]

[[Image:White dwarf stars browse.jpg|thumb|White Dwarf Stars photographed by the Hubble Space Telescope.]]

A '''White dwarf''' is a [[star]] that is the electron-degenerate remnant of a former star that has exhausted the nuclear fuel in its core and subsequently lost it's outer layers. They represent the final stage of [[Stellar_Evolution|stellar evolution]] for most stars, including our own [[Sun]].<ref>http://adsabs.harvard.edu/abs/2001PASP..113..409F</ref>    White dwarfs are extremely dense - a white dwarf with a mass equivalent to our Sun would have its material compacted into a volume no greater than the Earth.  As there is no more thermonuclear fusion within white dwarfs, their only source of [[light]] and [[heat]] is leftover thermal energy.

A '''White dwarf''' is the electron-degenerate remnant of a [[star]] that has exhausted the nuclear fuel in its core and subsequently lost its outer layers. It represents the final stage of [[Stellar_Evolution|stellar evolution]] for most stars, including our own [[Sun]].<ref>http://adsabs.harvard.edu/abs/2001PASP..113..409F</ref>    White dwarfs are extremely dense - a white dwarf with a mass equivalent to our Sun would be compacted into a volume no greater than the Earth.  As there is no more thermonuclear fusion within white dwarfs, their only source of [[light]] and [[heat]] is leftover thermal energy.

Typically any star between 0.5 and 8 solar masses will end its life as a white dwarf.  Most of these dwarfs are primarily made up of [[carbon]] and [[oxygen]], however stars of 4 solar masses or more will have the ability to fuse carbon, which will result in a white dwarf chiefly made up of oxygen, [[neon]], and [[magnesium]].<ref>http://adsabs.harvard.edu/abs/2005ASPC..334..165W</ref>  Any star greater then 8 solar masses will eventually develop a core that will be too massive to support by electron-degeneratcy (the [[Chandrasekhar limit]]) and collapse.  This collapse will result in a [[supernova]], and depending on the star's mass, the end result will be a [[neutron star]] or a [[black hole]].

Typically any star between 0.5 and 8 solar masses will end its life as a white dwarf.  Most of these dwarfs are primarily made up of [[carbon]] and [[oxygen]], however stars of 4 solar masses or more will have the ability to fuse carbon, which will result in a white dwarf chiefly made up of oxygen, [[neon]], and [[magnesium]].<ref>http://adsabs.harvard.edu/abs/2005ASPC..334..165W</ref>  Any star greater then 8 solar masses will eventually develop a core that will be too massive to support by electron-degeneratcy (the [[Chandrasekhar limit]]) and collapse.  This collapse will result in a [[supernova]], and depending on the star's mass, the end result will be a [[neutron star]] or a [[black hole]].

==Formation of White Dwarfs==

==Formation of White Dwarfs==

When  star that has a mass of less then 8 solar masses reaches the end of its life on the main sequence by consuming all of its [[hydrogen]] fuel in the core, all but the least masseive (less than 0.5 solar masses) will enter the [[red giant]] phase of its evolution.  At this point the core of these stars will become hot enough to fuse [[helium]] into carbon and oxygen.  For most of these stars, the core will cease fusion once all the helium is consumed, not having the sufficient mass to raise the temperature enough to fuse carbon.  For the heaviest stars under 8 solar masses though, carbon fusion will occur, but once all the carbon in the core is consumed, there is not enough heat to fuse the heavier elements available (usually oxygen, and neon).

When  star that has a mass of less then 8 solar masses reaches the end of its life on the main sequence by consuming all of its [[hydrogen]] fuel in the core, all but the least massive (less than 0.5 solar masses) will enter the [[red giant]] phase of its evolution.  At this point the core of these stars will become hot enough to fuse [[helium]] into carbon and oxygen.  For most of these stars, the core will cease fusion once all the helium is consumed, not having the sufficient mass to raise the temperature enough to fuse carbon.  For the heaviest stars under 8 solar masses though, carbon fusion will occur, but once all the carbon in the core is consumed, there is not enough heat to fuse the heavier elements available (usually oxygen, and neon).

At this point the star will have a carbon-oxygen core (or for the higher mass stars, a oxygen-neon core) surrounded by an inner shell of helium and an outer shell of  hydrogen.  The shells of hydrogen and helium will then be expelled and form a [[planetary nebula]] around the star, exposing the remnant core which is the white dwarf the vast majority being the carbon-oxygen variety.<ref>http://www.vikdhillon.staff.shef.ac.uk/teaching/phy213/phy213_lowmass.html</ref>

At this point the star will have a carbon-oxygen core (or for the higher mass stars, a oxygen-neon core) surrounded by an inner shell of helium and an outer shell of  hydrogen.  The shells of hydrogen and helium will then be expelled and form a [[planetary nebula]] around the star, exposing the remnant core which is the white dwarf the vast majority being the carbon-oxygen variety.<ref>http://www.vikdhillon.staff.shef.ac.uk/teaching/phy213/phy213_lowmass.html</ref>