I mean … is there any other type of explosive, combustible, or flammable reaction known to man that ends its reaction with a terrific explosion that’s more powerful than any of the other combustions prior to the end? It honestly seems like stars are the only things in the universe that end their lives that way. How come?
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It is important to note that only some stars explode! Of course, they are the spectacles and get the attention, but there are other ways that stars change status.
To help make sense of what happens to stars, it helps to think of a nuclear bomb. A star is basically a self-sustaining nuclear bomb. A nuke works by having the bomb “capsule” control the density of the material intended to go “bang”, a star does this by having a vast amount of gravity (far more than occurs naturally on Earth). With a bomb, the ‘control’ of the materials goes away once the explosion happens and the reaction fizzles out, but in a star the gravity is consistent and the reaction just keeps happening until there is no more material that can go bang.
With that in mind, you know how a nuclear bomb makes that big cloud? That’s what happens in a star, too, the big pressure cloud pushing out material. In a bomb, it doesn’t take very long before the material of the bomb runs out and the cloud collapses, while a star can run for thousands or billions of years (they have a lot of material). How big, what color, and what temperature a star is depends on how much and what kind of material it’s made of.
As the star burns it ‘converts’ the material it is made of, eventually it runs out of convertible fuel, but that material doesn’t go away. It just changes into something the star can’t convert, it’s essentially dead weight — but dead weight that still creates gravity.
If a star is converting helium into a variety of metals and heavy elements, and it starts to run out of fuel, it tends to get fluffy due to [physics]; basically the core remains as it is full of dead/useless fuel and the “active” fuel is creating an ever fluffier “atmosphere” due to the constant “blowing” the nuclear reactions are producing.
Once the “active” fuel runs out, that fluffy atmosphere no longer has the blowing that creates the fluff and gravity takes over. The “atmosphere” collapses suddenly, but it is so sudden that the material ends up reacting with itself and the star blows itself apart from the kinetics of the situation. If you’ve ever dropped a big rock into a small pond and get a big kersploosh you’ll have a sense of what a large mass can do to a liquid or gas if the impact is sudden enough. In astronomical terms, the star’s atmosphere collapses and literally craters itself, but instead of leaving behind one crater on one face of the star, the entire star is the crater everywhere at once. The entire star (except for the little bit of the core) craters itself in a titanic explosion that we see as a nova or supernova. The core then either collapses into a blackhole if it’s big enough, or if it’s not big enough for a black hole then it collapses into a neutron star, pulsar, magnetar, etc (you’ll hear various names).
BUT! a star like our sun is too small to hold onto the fluffiness with gravity. When a star like our sun enters the fluffy stage, the atmosphere is shuffed off completely (you’ve seen planetary nebular pictures, basically gas clouds with a tiny star in the middle, [like this](https://en.wikipedia.org/wiki/Planetary_nebula#/media/File:N1535s.jpg)). Once the active fuel runs out and the nuclear “puffing” stops, there is very little stellar “atmosphere” left to collapse, it’s all out either in orbit far away or it was ejected from the star system entirely due to the lower gravity of the smaller star. Once the puffing stops, the remnant “waste fuel” or “dead fuel” is just left as a lump. It’s still really hot, and a white dwarf can take millennia to cool, if not millions of years. Remember, in space there is no one going around dumping cold water on the campfire embers, these dead cores are just dead in the vacuum of space. You could say these smaller stars (like our Sun) “fizzle” to use your phrase from the title question. [https://en.wikipedia.org/wiki/White_dwarf](https://en.wikipedia.org/wiki/White_dwarf)
In theory, any planets around a star that goes nova should be destroyed but a few have been discovered to have survived, though it could be argued that these planets were captured rogues that were caught after the nova happened. Meanwhile, in a system like ours the planets may well survive but life probably will not considering that the Earth will be the equivalent of Mercury during the fluffy stage and will probably be right up against the sun’s surface for a while. Still, a white dwarf (the dead smaller stars) are hot enough for long enough that, in theory, life could start again on the sterilized worlds if conditions can return to “favorable”. Or a civilization like ours could move into space structures or more distant worlds (eg. drag asteroids further out and build cities inside them) and then move back and re-habit the planet if it’s not completely melted to nothing once the fluffy stage ends.
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