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A white dwarf is a stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very dense: in an Earth sized volume, it packs a mass that is comparable to the Sun. No nuclear fusion takes place in a white dwarf; what light it radiates is from its residual heat. [1]
If a white dwarf forms a close binary system with another star, hydrogen from the larger companion may accrete around and onto a white dwarf until it gets hot enough to fuse in a runaway reaction at its surface, although the white dwarf remains below the Chandrasekhar limit. Such an explosion is termed a nova.
Carbon detonation or carbon deflagration is the violent reignition of thermonuclear fusion in a white dwarf star that was previously slowly cooling. It involves a runaway thermonuclear process which spreads through the white dwarf in a matter of seconds, producing a type Ia supernova which releases an immense amount of energy as the star is blown apart.
White dwarfs are the slowly cooling stars that have cast off their outer layers during the last stages of their lives. Hubble discovers hydrogen-burning white dwarfs enjoying slow ageing Skip to ...
There are two predominant processes by which stellar hydrogen fusion occurs: proton–proton chain and the carbon–nitrogen–oxygen (CNO) cycle. Ninety percent of all stars, with the exception of white dwarfs, are fusing hydrogen by these two processes. [21]: 245
The theory of this type of supernova is similar to that of novae, in which a white dwarf accretes matter more slowly and does not approach the Chandrasekhar limit. In the case of a nova, the infalling matter causes a hydrogen fusion surface explosion that does not disrupt the star. [13]
If the accretion rate is just right, hydrogen fusion may occur in a stable manner on the surface of the white dwarf, giving rise to a supersoft X-ray source, but for most binary system parameters, the hydrogen burning is thermally unstable and rapidly converts a large amount of the hydrogen into other, heavier chemical elements in a runaway ...
Some result from white dwarfs in binary systems but others are very massive stars. (Classical) novae: These cataclysmic variables have very large outbursts, of 6 to 19 magnitudes, caused by thermonuclear fusion of material accreted onto the white dwarf. Recurrent novae These have outbursts of about 4 to 9 magnitudes, repeating every 10 to 80 ...