Type Ia supernova

A Type Ia supernova (read: "type one-A") is a type of <a href="/facts/Supernova/Pfo2J23l">supernova</a> that occurs in <a href="/facts/Binary_system/9aRPc441">binary systems</a> (two <a href="/facts/Star/PFbd6ICx">stars</a> orbiting one another) in which one of the stars is a <a href="/facts/White_dwarf/gIYlTtrC">white dwarf</a>. The other star can be anything from a <a href="/facts/Giant_star/kMseY7qf">giant star</a> to an even smaller white dwarf.
Physically, carbon–oxygen white dwarfs with a low rate of rotation are limited to below 1.44 solar masses (<a href="/facts/Solar_mass/j6Auhku8">M☉</a>). Beyond this "<a href="/facts/Chandrasekhar_limit/KojyANXK">critical mass</a>", they reignite and in some cases trigger a supernova explosion; this critical mass is often referred to as the Chandrasekhar mass, but is marginally different from the absolute <a href="/facts/Chandrasekhar_limit/KojyANXK">Chandrasekhar limit</a>, where <a href="/facts/Electron_degeneracy_pressure/fupuyb5c">electron degeneracy pressure</a> is unable to prevent catastrophic collapse. If a white dwarf gradually accretes mass from a binary companion, or merges with a second white dwarf, the general hypothesis is that a white dwarf's core will reach the ignition temperature for <a href="/facts/Carbon_burning_process/MbHbTB03">carbon fusion</a> as it approaches the Chandrasekhar mass. Within a few seconds of initiation of nuclear fusion, a substantial fraction of the matter in the white dwarf undergoes a <a href="/facts/Thermal_runaway/r5F7nfeY">runaway</a> reaction, releasing enough energy (1×1044 <a href="/facts/Joule/9ndq9jD2">J</a>) to unbind the star in a supernova explosion.
The Type Ia category of supernova produces a fairly consistent peak luminosity because of the fixed critical mass at which a white dwarf will explode. Their consistent peak luminosity allows these explosions to be used as <a href="/facts/Standard_candle/Xae3hVvK">standard candles</a> to measure the distance to their host galaxies: the <a href="/facts/Visual_magnitude/7pCTF1Me">visual magnitude</a> of a type Ia supernova, as observed from Earth, indicates its distance from Earth.

Type Ia supernova open-in-new

Type Ia supernova