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[[Image:Crab vlt big.jpg|right|thumb|The Crab Nebula]]

[[Image:Crab vlt big.jpg|right|thumb|The [[Crab Nebula]]]]

A '''supernova''' is a large stellar explosion that releases a tremendous amount of energy and destroys the star in which it originated. There are two types of supernovas, called, easily enough, type I and type II

A '''supernova''' is a large stellar explosion that releases a tremendous amount of energy and destroys the star in which it originated.<ref>{{cite web|url=https://www.britannica.com/science/supernova|title=Supernova|accessdate=2019-03-31}}</ref> There are two types of supernovas, called, easily enough, type I and type II

==Type I==

==Type I==

===Type 1a===

===Type 1a===

[[Image:Ia_Supernova.jpg|right|thumb|Theory on how type Ia supernova occur]]

[[Image:Ia_Supernova.jpg|right|thumb|Theory on how type Ia supernova occur]]

Although the exact mechanism that causes type I supernovae is still not entirely understood, for type Ia supernovae, it is generally accepted to occur most often in binary star systems where one of the binary stars is a white dwarf (typically a [[carbon]]-[[oxygen]] dwarf) that is drawing mass from its high mass companion. As the mass from from the companion accumulates on the surface of the [[white dwarf]] it compresses and heats up. Often, the hydrogen in the accumulated mass will heat enough to initiate hydrogen fusion, causing a [[nova (star)|nova]]. If however the white dwarf accumulated enough matter from its companion to achieve a mass that surpasses its [[Chandrasekhar limit]], the white dwarf will no longer be able to support itself via electron degeneracy pressure against the increase in [[gravity]] from the additional mass.<ref>http://adsabs.harvard.edu/abs/1987ApJ...323..140L</ref> A significant portion of the white dwarf will then undergo nuclear fusion within seconds, releasing enough energy to cause the star to explode as a supernova.<ref>http://www.sciencemag.org/cgi/content/abstract/315/5813/825</ref>

Although the exact mechanism that causes type I supernovae is still not entirely understood, for type Ia supernovae, it is generally accepted to occur most often in binary star systems where one of the binary stars is a white dwarf (typically a [[carbon]]-[[oxygen]] dwarf) that is drawing mass from its high mass companion. As the mass from from the companion accumulates on the surface of the [[white dwarf]] it compresses and heats up. Often, the hydrogen in the accumulated mass will heat enough to initiate hydrogen fusion, causing a [[nova (star)|nova]]. If however the white dwarf accumulated enough matter from its companion to achieve a mass that surpasses its [[Chandrasekhar limit]], the white dwarf will no longer be able to support itself via electron degeneracy pressure against the increase in [[gravity]] from the additional mass.<ref>Lieb, E. and Yau, H. (1987). A rigorous examination of the Chandrasekhar theory of stellar collapse. ''The Astrophysical Journal'', 323, p.140. [https://ui.adsabs.harvard.edu/#abs/1987ApJ...323..140L/abstract Bibcode: 1987ApJ...323..140L]</ref> A significant portion of the white dwarf will then undergo nuclear fusion within seconds, releasing enough energy to cause the star to explode as a supernova.<ref>Mazzali, P., Ropke, F., Benetti, S. and Hillebrandt, W. (2007). A Common Explosion Mechanism for Type Ia Supernovae. ''Science'', 315(5813), pp.825-828. [https://ui.adsabs.harvard.edu/#abs/2007Sci...315..825M/abstract Bibcode: 2007Sci...315..825M] [https://arxiv.org/abs/astro-ph/0702351 arXiv:astro-ph/0702351]</ref>

Type Ia supernovae are important to [[astronomy]] because they act as standard candles for measuring extra-galactic distances, especially pertaining to other galaxies.  This is due to such supernovae explosions having the same luminosity, an absolute magnitude of -19.3 (some five billion times the sun's brightness).  The source of this brightness is the generated by radioactive decay of nickel-56.  The [[nickel]]-56 is formed during the explosion event itself and decays through [[cobalt]]-56 to [[iron]]-56.<ref>http://adsabs.harvard.edu/abs/2000ARA&A..38..191H</ref>   

Type Ia supernovae are important to [[astronomy]] because they act as standard candles for measuring extra-galactic distances, especially pertaining to other galaxies.  This is due to such supernovae explosions having the same luminosity, an absolute magnitude of -19.3 (some five billion times the sun's brightness).  The source of this brightness is the generated by radioactive decay of nickel-56.  The [[nickel]]-56 is formed during the explosion event itself and decays through [[cobalt]]-56 to [[iron]]-56.<ref>http://adsabs.harvard.edu/abs/2000ARA&A..38..191H</ref>