Re: Supernova/mass extinction business

[larrys@zk3.dec.com]

>225 million years is about one galactic rotation at the Sun's location, and
>is vastly longer than the lifetime of an identifiable explosion signature

Okay, I can dig that - but we know the motions of all the stars
in our vicinity, and a star some 35 lightyears from us that went
nova _would_ leave a black hole, pulsar or white dwarf whose proper
motion could be backtracked to that point.  If we don't even have
some suspicious candidates for such a star, then this exercise is
pure, 100% speculation, no more valid than claiming they went extinct
because God willed it to be so.  A relative motion of, say, 10 miles
per second should still place the object within a sphere of around
2500 ly.  There's a lot of stars in that sphere, but the number of
nova remnants isn't very large.  Backtracking motion to a ring around
the Earth where such destruction must have originated cannot be that
hard.

regards,
Larry