White dwarfs are thought to be the final evolutionary state of all stars whose mass is not high enough to become a neutron star—over 97% of the stars in our galaxy.[5], §1. After the hydrogen–fusing lifetime of a main-sequence star of low or medium mass ends, it will expand to a red giant which fuses helium to carbon and oxygen in its core by the triple-alpha process. If a red giant has insufficient mass to generate the core temperatures required to fuse carbon, around 1 billion K, an inert mass of carbon and oxygen will build up at its center. After shedding its outer layers to form a planetary nebula, it will leave behind this core, which forms the remnant white dwarf.[6] Usually, therefore, white dwarfs are composed of carbon and oxygen.

Supernovae are classified as Type I if their light curves exhibit sharp maxima and then die away smoothly and gradually. The model for the initiation of a Type I supernova is the detonation of a carbon white dwarf when it collapses under the pressure of electron degeneracy. It is assumed that the white dwarf accretes enough mass to exceed the Chandrasekhar limit of 1.4 solar masses for a white dwarf. The fact that the spectra of Type I supernovae are hydrogen poor is consistent with this model, since the white dwarf has almost no hydrogen. The smooth decay of the light is also consistent with this model since most of the energy output would be from the radioactive decay of the unstable heavy elements produced in the explosion.

α CMa B Mass 0.978[6] M☉

Originally posted by artistpoet
reply to post by artistpoet

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The diagram you posted does not fit the Sirius system - if it did Sirius A would be a red giant yet it is millions of years away from becoming a red giant as is our Sun which is mid way through its cycle

edit on 24-1-2012 by artistpoet because: typos

Originally posted by xacto

Originally posted by artistpoet
reply to post by artistpoet

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The diagram you posted does not fit the Sirius system - if it did Sirius A would be a red giant yet it is millions of years away from becoming a red giant as is our Sun which is mid way through its cycle

edit on 24-1-2012 by artistpoet because: typos

I made the connection as well. My thinking is that maybe we don't know about supernovae and binary interaction as well as we should, yet here we have a fine specimen that is right next door. Surely we can observe it with all of our best tools and minds and learn much about it!