[vsnet-chat 1591] (fwd) Re: (fwd) Type II supernovae

[Daisaku Nogami <nogami@kusastro.kyoto-u.ac.jp>]

 Subject: Re: [vsnet-chat 1582] (fwd) Type II supernovae 
 Date: Mon, 25 Jan 1999 23:19:09 -0500
 From: Stupendous Man <richmond@a188-l009.rit.edu>

  This is a complicated topic!  There are several complications which
make it difficult to predict the brightness of a supernova explosion,
based on the mass of the progenitor.

     a. a star which starts out its life with, say, 20 solar masses
            of material will LOSE some of that mass during its 
            lifetime.  In general, the more massive a star is,
            the greater a fraction of its initial mass it expels
            as a stellar wind before it reaches the supernova state.
            So a star which is born with 20 solar masses might have
            only 16 solar masses of material left when it reaches
            the supernova stage.

     b. we don't understand how and why stars expel some of their
            mass via stellar winds during their lifetimes, so we 
            cannot predict accurately how much material will be
            left when they are ready to explode.

     c. the brightness of a supernova depends on the exact density
            structure of its outer layers when it explodes; we don't
            know enough of the details of stellar evolution to predict
            that structure precisely.

     d. the brightness of a supernova can depend strongly on the amount
            of gas and dust immediately surrounding it; this may be
            material shed by the star via a stellar wind before it 
            explodes.  Once again, our models of stellar evolution
            don't permit us to predict this circumstellar environment
            very accurately.

  So there are too many variables for me to be able to predict a simple
relationship between the initial mass of a star at its birth
and the brightness of its supernova explosion.  It's possible that
there _is_ a simple relationship -- but I don't know it.

                               Michael Richmond

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