From: Henry Spencer <henry@zoo.toronto.edu>
Newsgroups: sci.space.science
Subject: Re: Betelgeuse supernova?
Date: Mon, 8 Apr 1996 17:41:45 GMT

In article <31655AE0.2119@dimensional.com> seale@dimensional.com writes:
>...I remember seeing another paper that mentioned
>the suspected "periodic" extinction events occurred when the solar
>system was near its greatest out-of-plane (of the galaxy) positions.

Actually, no, this doesn't work out.  For one thing, the evidence for
any sort of periodicity in extinction events is extremely weak -- more
an artifact of the statistics than a believable result, at least with
today's data.

For another, there is no plausible mechanism by which the out-of-plane
excursions could account for such a periodicity, simply because the Sun
doesn't go very far out of the plane of the galaxy -- at least, not with
its present orbital elements -- and the density of known types of objects
does not fall off that sharply with distance from the plane.  The Sun's
environment simply doesn't vary terribly much with its out-of-plane
excursions.

For lots more detail, although not the very latest news, see "The Galaxy
and the Solar System", Smoluchowski/Bahcall/Matthews eds., U of Arizona.
-- 
Americans proved to be more bureaucratic           |       Henry Spencer
than I ever thought.  --Valery Ryumin, RKK Energia |   henry@zoo.toronto.edu