From: Reason (reason@exratio.com)
Date: Fri Dec 20 2002 - 00:57:32 MST
My first masters thesis back in 95' had a few answers to this question. I
was modelling the stellar interiors of varying metallicity and mass
Population III stars (zero, little bit more than zero, etc, all the way up
to low-end population II). The idea was to come up with a range of plausible
mass functions and plug some numbers in to see how quickly the early
universe could generate low-end Population II metallicities.
[Metals in stars -- carbon and up -- are very strong sources of opacity, or
coupling of radiation to matter. This makes even tiny amounts of metals by
mass have huge effects on stellar evolution and upper mass limits].
So it turns out that with very little metallicity, you can have
100Msol-1000Msol quasi-stable stars that go supernova in under a million
years from ignition. Unfortunately, it's hard to say how much of the metal
gets out -- the software and physics just really wasn't up to that at the
time. You also have extremely long-lived tiny stars (as in they should still
be around now, everywhere), which we ruled out with some BOTE calculations
based on existing astronomy. When the math tells you there are a thousand
magnitude 18-21 objects within ten light years of us, the initial input is
wrong :)
Anyway, current upper bound in mass is thought to be 40-100Msol, depending
on who you want to believe. Low end, more likely. It's entirely
metallicity-determined. If you know the composition and mass of a star,
everything else follows from that.
Reason
http://www.exratio.com/
> -----Original Message-----
> From: owner-extropians@extropy.org
> [mailto:owner-extropians@extropy.org]On Behalf Of Jeff Davis
> Sent: Thursday, December 19, 2002 9:32 PM
> To: extropians@extropy.org
> Subject: Re: Panspermia
>
>
> Question:
>
> In the first star-forming era after the big band, when
> all the stars are composed of hydrogen and helium,
> what is thought to be the upper bound for the mass of
> H/He supergiant stars? What factors contribute to
> this limit/boundary?
>
> If these stars proceed most rapidly to the
> (super?)nova state (that's how it works, right?)--and
> with it heavy-element (heavier than carbon,
> right?)nucleosynthesis--what then is thought to be the
> shortest possible stellar 'lifetime'?
>
> Best, Jeff Davis
>
> "Believe nothing, no matter where you read it, or who
> said it--no matter if I have said it--unless it agrees
> with your own reason and your common sense."
> Buddha
>
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