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From: Bill Sloman <bill.sloman@ieee.org>
Newsgroups: sci.electronics.design
Subject: Re: OT: Dark energy might not be constant at all
Date: Sat, 6 Apr 2024 02:16:17 +1100
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On 6/04/2024 1:28 am, John Larkin wrote:
> On Fri, 5 Apr 2024 09:17:23 +0100, Martin Brown <'''newspam'''@nonad.co.uk> wrote:
>> On 05/04/2024 06:17, Jan Panteltje wrote:

> 10^44 joules could fry a thousand civilizations. We're lucky to live
> in a boring suburb of the universe.

Supernova pop up all over - just not all that often. There's nothing 
unique about our suburb of the universe - corner of the galaxy might be 
a better way of referring to our immediate vicinity

> Are those things the sources of our heavy elements?

That seems to be the current working hypothesis. Anything up to iron - 
26 protons and 30 neutrons in the most common isotope Fe-56 (91.754%)

<https://en.wikipedia.org/wiki/Isotopes_of_iron>

can be synthesised in mainstream star, but it has the largest mass 
defect of any element. Fe-54, Fe-57 and Fe-58 are the other stable isotopes.

Getting anything heavier takes a supernova - gravitational pressure 
exceeds nuclear repulsion and all the matter at the core of the star 
collapses into neutron soup, but if the star isn't heavy enough to 
become a black hole the collapsing soup that was moving inward very fast 
until it hit it's density limit mostly bounced back out again and 
reverted from neutron soup to regular matter that included a lot of 
elements heavier than iron. The heaviest ones fissioned rapidly, but 
rest provide all the elements from iron upwards to uranium and the like.

They weren't there in the very early universe, and the second generation 
stars don't have all that much of them.

-- 
Bill Sloman, Sydney