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Distances to Supernovae
Type Ia supernovae are “standard candles”
Occur in a binary system in which a white dwarf star accretes beyond the 1.4 Mo Chandrasekhar limit and collapses and explodes
Decay time of light curve is correlated to absolute luminosity
Luminosity comes from the radioactive decay of Cobalt and Nickel into Iron
Some Type Ia supernovae are in galaxies with Cepheid variables
Good to 20% as a distance measure
Notes:
The Pleiades contains over 3000 stars, is about 400 light years away, and only 13 light years across. Quite evident in the above photograph are the blue reflection nebulae that surround the bright cluster stars. Low mass, faint, brown dwarfs have recently been found in the Pleiades.