Changes

===Type 1a===

===Type 1a===

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]].  If however the white dwarf accumulated enough matter from its companion to have a mass that reaches 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]].  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>

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>.