Supernova, neutrinos, extinctions

[keel@bildad.astr.ua.edu (William Keel)]

I've sat on my hands as long as I could manage...

Thomas Lipka wrote:
This is yet another rehash of the old supernova hypothesis that remains to
this day debunked. I do not have a ref in front of me but I am nearly certain
that there is NO evidence for a supernova anywhere near the earth that date
anywhere near 65Ma. It seems that a "close by" supernova cannot be proved so
the've gone fishing for more far fetched ones! I also believe that since
neutrinos are nearly massless and have a _mean_free_path_ that is equivalent
to the earths diameter(!) that it would take enourmous neutrino fluxes to
 even have enough of them interact with an animal's atoms/molecules to even
register an effect. If there was to be a supernova, it would have to be alot
closer. Cosmic/gamma rays would be the more likely cause if there were a
supernova to talk about.

----------------------------------------------------------------------------------
We might have had this discussion before, but supernova remnants themselves
(the gaseous expanding explosion bubbles) fade below detectability after
times of order 20,000 years. After that, one would seek the neutron star
(or perhaps black hole) remaining - and one has to be very lucky to find
one, in terms of orientation and immediate environment. On top of that,
after 65 million years, the typical random motions among even those stars
most nearly sharing the Sun's motion would move an originally nearby object
at least 200 l.y. with respect to the Sun - and our census for compact objects
is nowhere near that complete. N

None of this is to say that I would swallow the neutrino-cancer business. As
(if I recall correctly) Tom Holtz passed on, it has been common lore in the
nuclear-astrophysics biz that, for a planet of the exploding star, the neutrinos
would kill you before the blast, but the, umm, kill radii are comparable.
Mind you, that's a lot of neutrinos, and this guy was talking about
a neutrino flux 10^8 times that from SN 1987A - but for my money, you'd
need to be i nthe same planetary system, and that would leave no fossils.
.. And I thought _Nature_ had erratic editing...

Bill "careful not to mention morphology or synapomorphies" Keel
Astronomy, University of Alabama