system
Given the following post, respond as if you're commenting on Reddit:
human
What would happen if you poured a sun-sized bucket of water over the sun?

Would it just go out? Like, poof, it’s gone? Would it solidify into something? Would all the water vaporize? I feel like it would all vaporize but it’s the same amount of water as there is sun, so it just feels like it *couldn’t* all vaporize, y’know? 

Also how much water would it take to “put out” the sun? 

(Totally not asking because of any nefarious plans /s)
gpt
The Sun is not "on fire" so you can't put it out with water. The Sun creates its energy from nuclear fusion, and that is all happening in the core of the Sun, so the fusion would continue. But, if you did drop a "sun sized" bucket of water on the Sun, you'd kill us all. 

The Sun is in hydrostatic equilibrium- which is a fancy way of saying the forces pulling the Sun in, to collapse, are matched by the forces pushing out on the Sun. What are the forces? Well, the nuclear fusion is creating force pushing out. And gravity is the force pulling it in. It is not a coincidence that it is in equilibrium, of course. As gravity pulls to collapse the Sun, it increases the density of the core. As the density increases, the rate of fusion increases. This then, creates a greater outward force, and things go back into equilibrium. 

So, this water that gets dumped on the Sun would be gravitationally bound to the Sun. So sure, it would vaporize, but the mass would stay the same. And a bucket full of water the "size of the Sun" would have 71% of the mass of the Sun (aka, water is 70% as dense as the Sun) and whether that's in the form of water or steam, the mass is the same. So, now the Sun has 1.7x the mass it used to have. This means, the gravitational force trying to collapse the Sun increases- and as we discussed, that would mean the rate of fusion would increase. And if the rate of fusion increased, that would mean the temperature of the Sun would increase as well. At only 1.7 Solar Masses, you would still be under the limit for a "Intermediate Size Star", so we would stay on the same nuclear fusion chain, just for much shorter period of time. Instead of the Sun lasting another 10 billion years or so, we'd be closer to completing it's main cycle (aka- the cycle that converts hydrogen to helium) in about 3 Billion years, meaning we'd essentially triple the output from the Sun. This would mean the temperature on Earth would become completely inhospitable. 

This would also have an incredibly nasty effect on the orbit of the Earth, as the orbit would become highly elliptical (assuming the water appeared suddenly), and we'd spend quite a bit of time much closer to the Sun. Combined with the extra output from the Sun, and we're even more toast that otherwise would be.