Re: Plate techtonics and asteroid hits

In article <7StJsaIeTxnGFwt3@xxxxxxxxxxxxx>,
Ernest Major <{$to$}@meden.demon.co.uk> wrote:

In message
<timberwoof.spam-54EDE9.17261218072007@xxxxxxxxxxxxxxxxxxxxxxxx>,
Timberwoof <timberwoof.spam@xxxxxxxxxxxxxxxxxxxxx> writes

Uhm... How do we know how long a supernova is supposed to take to
happen?


Observation and theory.

To simplify, perhaps to the point of inaccuracy ...

One form of supernova occurs when the core of a massive star collapses.
This results in the expulsion of large quantities of hot matter, and the
formation of a large quantities of Ni-56, which decays to Co-56 and then
to Fe-56. We can observe the decay of luminosity of such supernovae
matching the half-life of Ni-56. (IIRC, Co-56 has a much shorter
half-life, and therefore doesn't accumulate in large quantities.)

Another form occurs when sufficient matter is deposited on the surface
of a white dwarf to take it over the Chandrasekar Limit, whereupon it
collapses into a neutron star. Members of this class are very similar -
they can be used as standard candles - and presumably last much the same
time.

Thanks for the explanation.

Hm. It seems to me that variations in initial conditions, such as the
mass of the star (or the masses of the white dwarf and its companion),
would have effects greater than delta-T expected from delta-V. Point me
to a paper? :-)

--
Timberwoof <me at timberwoof dot com> http://www.timberwoof.com

.

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