okay so, nuclear physics is not really my thing...
a couple days ago, you mentioned that iron doesn't fuse into heavier elements - i remember reading this is because that's the point where the nucleus becomes heavy enough that fusion no longer releases net positive energy
so what's the deal with heavier elements? are they using the energy released by remaining lighter elements to provide the energy to fuse heavier-than-iron atoms? or something else?
so zhe deal wizh iron being a starkiller is zhat zhe star needs to be constantly producing energy to prevent gravitational collapse.
zhe zhing about supernovae is zhat zhere is just an ABSURD amount of energy present, and zhe vast majority of it is pure excess.
Abyzz
wizh all zhis extra energy around, zhe energy-consuming fusion pazhways have absolutely no issues finding zhe energy zhey need to fuse all zhe way to uranium
there's two ways to make elements heavier than iron: slow and rapid. very creatively these are known as the s- and r-processes.
in the slow process, heavier atoms randomly capture neutrons from the surrounding star soup in older giant stars (neutrons are released in some fusion reaction chains). if they're stable they become new isotopes, and if they become unstable that extra neutron can decay into a proton and presto, a new element!
the rapid process is much more explosive. happens during supernovae or neutron star collisions, you see. you just need a ridiculous amount of neutrons next to some iron and it's just like the s-process but...fast! heavier elements like gold are likely mostly generated by neutron star collisions!
when large stars die, they tend to leave behind heavier elements than what they started with, and that stuff is what new stars are born from. that's how you get different generations (usually called populations) of stars with different metallicity. the earliest stars (population III) where just hydrogen and helium but we still have no direct observation of them afaik
zhank you for zhe extra info! nukesci is FUN STUFF and it's very much outside my knowledge
I think it's cool that billions of years ago stars were slamming into each other or exploding to make new elements, some of which aren't stable enough to stick around. Then they all got scooped up by gravity and formed the solar system, little bits of that form the earth, most of the heavy stuff sinks to the core but some of it remains in the crust, all the way to today where that uranium is decaying into radon and giving some guy in Montana lung cancer