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From: friesen@psivax.UUCP (Stanley Friesen)
Newsgroups: net.space
Subject: Re:  Tenth planet
Message-ID: <926@psivax.UUCP>
Date: Mon, 6-Jan-86 11:47:18 EST
Article-I.D.: psivax.926
Posted: Mon Jan  6 11:47:18 1986
Date-Received: Wed, 8-Jan-86 06:44:32 EST
References: <> <923@nmtvax.UUCP> <6258@utzoo.UUCP>
Reply-To: friesen@psivax.UUCP (Stanley Friesen)
Organization: Pacesetter Systems Inc., Sylmar, CA
Lines: 26

In article <6258@utzoo.UUCP> henry@utzoo.UUCP (Henry Spencer) writes:
>
>Alas, Nemesis has met its fate :-).
>
>(Quick digression:  the theory alluded to here is the notion that periodic
>extinctions are caused by near approaches of a companion star, which is in a
>*very* long-period orbit [30MY or so], stirring up the Oort cloud and causing
>a rain of comets into the inner Solar System.)
>
>The problem with making the Sun a binary star is that Nemesis has to be a
>godawful long way out to have such a long orbital period, and it appears
>that such an orbit simply is not very stable over geological time scales.

	Another nail in the coffin. A recent re-analysis of the
original study(a statistical analysis of extinction rates) has
strongly suggested that the periodicity (actually 26MY) is wholely an
*artifact* of the statistical methodology used, in particular the
sampling method. The later study used a Monte-Carlo simulation of
uniform random extinctions and found that the method used by the
original study *still* showed a 26MY periodicity!
-- 

				Sarima (Stanley Friesen)

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