Beltstrike

I don't really have the thermo to do a BOTEC, but just as a PDOOMA I'd say at least on the order of a million years, depending on starting and desired ending temperatures.
Isaac Arthur has a neat video series on 'Civilizations At The End Of Time'; the era of the universe where there is no more fusion, all the luminous stars have sputtered out, and civilizations scavenge energy from the various remaining sources. 'Iron Stars' (the iron-rich remains of stellar cores after they reach end-of-life) take trillions of years to cool off. I'm not too sure, but I think the nickle-iron cores of planets last a similarly long time.
 
'Iron Stars' (the iron-rich remains of stellar cores after they reach end-of-life)
There's no such animal. Once a star begins burning silicon into iron, it's only minutes away from going supernova. (Once it starts burning oxygen not silicon it's got five years, tops. Life comes at you pretty fast.)

(Or is he talking about fusion by quantum tunneling in white dwarves? Ain't nobody got time to wait around for that to start to happen.)
 
There's no such animal. Once a star begins burning silicon into iron, it's only minutes away from going supernova. (Once it starts burning oxygen not silicon it's got five years, tops. Life comes at you pretty fast.)

(Or is he talking about fusion by quantum tunneling in white dwarves? Ain't nobody got time to wait around for that to start to happen.)
Only stars with more than eight solar masses go supernova (and then become either a neutron star or a black hole). Below that they become a white dwarf and cool off for trillions of years.
(yes, there are type 1a supernovas, but let's keep this simple).
 
Only stars with more than eight solar masses go supernova (and then become either a neutron star or a black hole). Below that they become a white dwarf and cool off for trillions of years.
(yes, there are type 1a supernovas, but let's keep this simple).
And the ones that don't go supernova don't produce iron.
 
Good point on the cooling time of a smashed core. Although since we're talking *half lives* and potentially large starting amounts, a million years or so may not be a major hinderance. Ten thousand tons with a half life of a million years is still 5000 tons a million years later (plus 5000 tons of potentially useful whatever stable element or isotope that it decayed into).
 
Good point on the cooling time of a smashed core. Although since we're talking *half lives* and potentially large starting amounts, a million years or so may not be a major hinderance. Ten thousand tons with a half life of a million years is still 5000 tons a million years later (plus 5000 tons of potentially useful whatever stable element or isotope that it decayed into).
It's not radioactive decay that's going on, it's radiative cooling. That happens at a rate proportional to the fourth power of the temperature, and I don't remember enough DiffEq to turn that into a closed form solution - I expect it would be something involving an exponential but not the plain exp(-t) of radioactive decay.

Just to be pedantic, I mean.
 
Oh, sure. I was just referring to core material that is radioactive, and how much might be left exposed, regardless of how thermally hot the rocks are.
 
And I don't have the physics to judge, but could an extrasolar planetary body that entered a solar system and collided with one of its planets create them? For the purposes of the discussion, assume the two bodies are on opposing vectors - a head on collision.

I would think at the very least it might make some interesting and useful minerals, even if no transmutation took place.
 
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