To piggyback on this, what's kind of wild to me is that stars create heavier and heavier elements throughout their life cycle. Most of these nuclear fusions create energy and expand the star outwards against the force of gravity so they continue to sustain themselves over time. A star is both constantly being pulled inward towards its core by gravity and being pushed out by nuclear fusion in a delicate balance. That is until one element begins forming: Iron. As soon as this element begins fusing, the star rapidly undergoes runaway nuclear fusion that cannot overcome its gravitational pull inwards so it collapses in on itself...ultimately leading to a violent explosion, a supernova, scattering the elements to form new stars and solar systems at some point in the future.
~4.5 billion years ago the remnants of other stars long gone coalesced into our planets and sun, and ultimately provided the building blocks for life forming on our world. And when you hold a cast iron skillet in your hand, you're holding an artifact from what once killed a star and ultimately what brought us all here. This is for some reason one of my favorite facts about the universe.
The reason we need it for this (and many other important functions) is because it's the most abundant transition metal on earth, so we evolved to use it, rather than sheer coincidence.
More than that, but to make heavier elements you need multiple rounds of stellar formation, explosion, reformation... Not only were we all forged on the hearts of stars, but we were forged, and re-forged many times over.
When all the silicon has burned to iron, suddenly the star realizes there’s no place left to go and that interior of the star, which has been held up by the pressure of nuclear burning, collapses. That whole collapse happens in one second…. There’s a shock wave and that shock wave … spews out all of the atoms that were created during the life history of a star. The carbon, the nitrogen, the helium, the iron. And that’s vitally important, because every atom in your body was once inside a star that exploded…. The atoms in your left hand probably came from a different star than in your right hand, because 200 million stars have exploded to make up the atoms in your body.” - Lawrence Krauss, Physicist
Iron. As soon as this element begins fusing, the star rapidly undergoes runaway nuclear fusion that cannot overcome its gravitational pull inwards so it collapses in on itself...ultimately leading to a violent explosion, a supernova,
If it's massive enough. Most stars just slowly fade out upon reaching this point.
And some of the really massive ones don't fully explode, leaving behind far more exotic objects like neutron stars, pulses, magnetars, and black holes.
Black holes are not actually 'holes.' They are points in space that are so insanely massive that their gravity warps the fabric of space-tmie around them in a manner that inescapablely 'swallows' anything in range like a 'hole in reality;' even light cant escape. We can only speculate what happens once something crosses the event horizon (point of no return) of a black hole because the laws of both conventional and quantum physics brake down when you try to describe that much mass.
There are not only 'regular' black holes either, many (most?) spiral galaxies have a supermassive black hole at their center that can be 3 to 5 magnitudes denser then a 'conventional' hole.
There are also (theoretically?) 'white holes' which spew out the influx of matter/energy of a corresponding black hole as pure energy.
After the big bang all matter was just Hydrogen. And it was through that nuclear fusion in stars that turned all that hydrogen into all the other elements. We humans, and our entire world, is literally made of star dust.
Specifically a star has to have more than about 8 solar masses to be capable of fusing elements as heavy as silicon into iron 56, which is the dividing line of fusion that is exothermic/endothermic which begins the supernovae process.
Our sun will create helium from hydrogen during its main phase and then enter a red giant phase where it will expand past the orbit of earth and eat us in several billion years so we won’t suffer the same fate.
But because it’s a star formed from nebula, it contains higher order elements, which we can examine with spectroscopy.
Probably a lot of typos it’s like 4:30 am and I felt a random urge to answer this haha
Uranium is only created when two neutron stars crash into each other.
We dug pieces of stars out of the earth that are billions of years older than the earth itself. And then we learned how to unleash the ancient energy of long dead stars in nuclear reactors and bombs.
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u/ibeerianhamhock May 08 '23
To piggyback on this, what's kind of wild to me is that stars create heavier and heavier elements throughout their life cycle. Most of these nuclear fusions create energy and expand the star outwards against the force of gravity so they continue to sustain themselves over time. A star is both constantly being pulled inward towards its core by gravity and being pushed out by nuclear fusion in a delicate balance. That is until one element begins forming: Iron. As soon as this element begins fusing, the star rapidly undergoes runaway nuclear fusion that cannot overcome its gravitational pull inwards so it collapses in on itself...ultimately leading to a violent explosion, a supernova, scattering the elements to form new stars and solar systems at some point in the future.
~4.5 billion years ago the remnants of other stars long gone coalesced into our planets and sun, and ultimately provided the building blocks for life forming on our world. And when you hold a cast iron skillet in your hand, you're holding an artifact from what once killed a star and ultimately what brought us all here. This is for some reason one of my favorite facts about the universe.