Hydrogen is the most abundant element in the universe, so hydrogen fusion is a cheap source of energy for (main-sequence) stars. As hydrogen runs out in a star’s core, it resorts to slightly more expensive helium fusion.
When the outward pressure of nuclear fusion falters, a star collapses in on itself. If the star is big enough, it may crunch down and then bounce back, resulting in a nova or supernova. Massive stars that go supernova can even continue past helium fusion, going on to make heavier and heavier elements. But eventually, all fuel-depleted stars take one of three forms, depending on their remaining mass:
- A dwarf (either white or black)
- A neutron star
- A black hole
That’s a pretty darned good summary of where everything is headed and why.
I always enjoyed the fact as well that if sentient (possibly un-sentient?) life maximizes its ability to split/fuse arbitrary atomic nuclei for energy, then all matter outside of the three things you listed will eventually be boiled down / fused up to Fe since Iron is the least energy potent of elements. The universe will be literally a iron giant and metaphorically a iron rusty hulk. Pretty ready for rebirth from the next big bang, in my opinion. I love astrophysics.
Is this a recent interest of yours, or are you planning to crank up a fusion device we don’t know about?
I am the fusion device.
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