Editing White dwarf (section)

== Fate ==
[[File:White Dwarf Ages.ogv|thumb|Artist's concept of white dwarf aging]]
[[File:Whitedwarfsevolution.png|thumb|Internal structures of white dwarfs. To the left is a newly formed white dwarf, in the center is a cooling and crystallizing white dwarf, and the right is a black dwarf.]]
Once formed, a white dwarf is stable and will usually continue to cool almost indefinitely, eventually to become a black dwarf. Assuming that the [[universe]] continues to expand, it is thought that in 10<sup>19</sup> to 10<sup>20</sup> years, the [[galaxy|galaxies]] will evaporate as their [[star]]s escape into intergalactic space.<ref name="fate">{{cite journal  |last1=Adams |first1=Fred C. |last2=Laughlin |first2=Gregory |date=1997 |title=A dying universe: The long-term fate and evolution of astrophysical objects |journal=Reviews of Modern Physics |volume=69 |issue=2 |pages=337–372 |arxiv=astro-ph/9701131 |bibcode=1997RvMP...69..337A |doi=10.1103/RevModPhys.69.337|s2cid=12173790 }}</ref>{{rp|§IIIA}} White dwarfs should generally survive galactic dispersion, although an occasional collision between white dwarfs may produce a new [[nuclear fusion|fusing]] star (eg. an [[extreme helium star]])<ref name=Jeffery_2014>{{cite journal | title=The origin and pulsations of extreme helium stars | last=Jeffery | first=C. Simon | journal=Precision Asteroseismology, Proceedings of the International Astronomical Union | series=IAU Symposium | volume=301 | pages=297–304 | date=February 2014 | doi=10.1017/S1743921313014488 | arxiv=1311.1635 | bibcode=2014IAUS..301..297J }}</ref> or a super-Chandrasekhar mass white dwarf that will explode in a [[Type Ia supernova]].<ref name="fate" />{{rp|§§IIIC, IV}} 

The lifetime of a white dwarf is thought to be on the order of the hypothetical lifetime of the [[proton]], known to be at least 10<sup>34</sup>–10<sup>35</sup> years. Some [[grand unified theory|grand unified theories]] predict a [[proton decay|proton lifetime]] between 10<sup>30</sup> and 10<sup>36</sup> years. If these theories are not valid, the proton might still decay by complicated nuclear reactions or through [[quantum gravity|quantum gravitational]] processes involving [[virtual black hole]]s; in these cases, the lifetime is estimated to be no more than 10<sup>200</sup> years. If protons do decay, the mass of a white dwarf will decrease very slowly with time as its nuclei decay, until it loses enough mass to become a non-degenerate lump of matter, and finally disappears completely.<ref name="fate" />{{rp|§IV}}

A white dwarf can also be cannibalized or evaporated by a companion star, causing the white dwarf to lose so much mass that it becomes a [[planetary mass object]]. The resultant object, orbiting the former companion, now host star, could be a [[helium planet]] or [[Carbon planet|diamond planet]].<ref name=2007ApJ...669.1279S>{{cite journal |title=Mass-Radius Relationships for Solid Exoplanets |last1=Seager |first1=S. |last2=Kuchner |first2=M. |last3=Hier-Majumder |first3=C. |last4=Militzer |first4= B. |journal=The Astrophysical Journal |volume=669 |issue=2 |pages=1279–1297 |publication-date=November 2007 |doi=10.1086/521346 |arxiv=0707.2895 |bibcode=2007ApJ...669.1279S |date=19 July 2007|s2cid=8369390 }}</ref><ref>{{cite journal |doi=10.1126/science.1208890 |title=Transformation of a Star into a Planet in a Millisecond Pulsar Binary |year=2011 |last1=Bailes |first1=M. |journal=Science |volume=333 |number=6050 |pages=1717–1720 |pmid=21868629 |arxiv=1108.5201 |bibcode=2011Sci...333.1717B |display-authors=etal}}</ref><ref name=TIME-2011-08-26>{{cite magazine |last=Lemonick |first= Michael |date=26 August 2011 |title=Scientists Discover a Diamond as Big as a Planet |url=http://www.time.com/time/health/article/0,8599,2090471,00.html  |magazine=[[Time (magazine)|Time Magazine]] |archive-url=https://web.archive.org/web/20130824010717/http://www.time.com/time/health/article/0,8599,2090471,00.html |archive-date=24 August 2013 |access-date=18 June 2015}}</ref>