Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.2 9/18/84; site psivax.UUCP
Path: utzoo!watmath!clyde!cbosgd!ukma!psuvm.bitnet!psuvax1!burdvax!sdcrdcf!psivax!friesen
From: friesen@psivax.UUCP (Stanley Friesen)
Newsgroups: net.astro
Subject: Re: Question about Sirius
Message-ID: <906@psivax.UUCP>
Date: Wed, 18-Dec-85 12:23:45 EST
Article-I.D.: psivax.906
Posted: Wed Dec 18 12:23:45 1985
Date-Received: Sat, 21-Dec-85 04:46:50 EST
References: <283@infinet.UUCP> <900@psivax.UUCP> <174@utastro.UUCP>
Reply-To: friesen@psivax.UUCP (Stanley Friesen)
Distribution: net
Organization: Pacesetter Systems Inc., Sylmar, CA
Lines: 53

Thank-you for your response, it has cleared things up considerably.

In article <174@utastro.UUCP> jeff@utastro.UUCP (Jeff Brown the Scumbag) writes:
>>
>>      Well, not by ordinary, simple collapse, but a supernove would
>> do it, assuming that some types of supernovas do not result in a
>> neutron star.
>
>That Sirius B is now less massive than Sirius A is not that unusual;
>  The problem is, as mentioned above, that
>the more massive a star is, the faster its evolution.  This is known
>as the "Algol paradox" since Algol (another famous binary star) has the
>same kind of trouble.  The way out is that the (now) less massive star was
>more massive and has lost a lot of mass, possibly (maybe even probably)
>dumping matter on the (now) more (but then less) massive star.

        I had heard of this phenomenon but I was unsure whether the
Sirius system was a close enough binary for this kind of mass exchange
to occur. Then as you mention below there is the mass loss to
planetary nebulae, which would still be visible if Sirius B had been a
red giant in historical times. Certainly we both agree that if Sirius B
*had* been a red giant in historical times there would still be easily
observed remnants of that condition in the Sirius system.
>
>  I have no
>objection to the assertion that Sirius B was once more massive than it
>is now and subsequently became a red giant en route to a white dwarf; I
>object strongly to the suggestion that it was a red giant as little as
>2000 years ago.  (Incidentally, that Sirius B is a white dwarf indicates
>that it did *not* supernova; supernovae don't leave white dwarfs behind.
>Also, you're right that a supernova that close to us would be Very Bad
>News Indeed.)
>
        I know that *one* type of supernova leaves a neutron star, but
I believe there are at least *three* different types of supernova,
each with a significantly different mechanism. So is it really
established that *none* of the types of supernova could possibly leave
a white dwarf ?? (Note: my main recent source is the article in
Scientific American a few months ago - I may have to reread the
article to refresh my memory on the different types of supernova)

>I think most astrophysicists would agree with me that it would take a lot
>more evidence than what we have to make us think it possible that the Sirius
>system has undergone a real change in color in recent history.

        To say the least, given the absence of any observable anomaly
in the system other than the Algol Paradox!
--

                                Sarima (Stanley Friesen)

UUCP: {ttidca|ihnp4|sdcrdcf|quad1|nrcvax|bellcore|logico}!psivax!friesen
ARPA: ttidca!psivax!friesen@rand-unix.arpa