The other tricky part is the composition of the Sun - when Jack says "We know what stars are composed of (at least on the outside)" it's because, as mentioned, light passing through gas is absorbed. If the FE Sun is a solid, luminescent object, we're still primarily measuring the gas that the light passes through between it and us. Most of what we can conclude is just 'this gas exists between the Sun and us.'
Is there enough redshift from the rotation of the sun to measure?
See, that's the problem. You have knowledge but no way of proving you know what you know. "We know it because of measurements of this machine." But you can't know if that machine is telling you correct information. Or it might be correct but irrelevant. When we measure the details of stars we don't bother to sing "How I wonder what you are..."
If you really want to go down this path, it means you literally cannot know anything at all.
That means you cannot know that Earth is flat, you cannot even know if Earth exists, or if you exist.
Most people do not operate with that meaning of the word "know", because it makes it entirely useless.
Even more foolish than me declaring they could be angels (What? We haven't disproven that) is you telling us that you know, because a spectroscope told you, when you've maybe shown chemical composition not the nature of things. You've told me what individual stars are made of. But neither of us knows what they are.
No, you claiming they could be angels, with absolutely nothing to support it, is far more foolish than the everyday use of the word know.
Again, one idea is supported by plentiful evidence and a coherent model.
The other is just wilful rejection to try and prop up an incoherent delusional fantasy.
The way you people like to skim quotes, you probably read "it's already been done" and stop. But the key here is "small scale and last for just a few seconds at most". Were scientists to succeed, it would be the last in a long line of disasters made because scientists have no moral compass. The last because it would destroy the world having a second sun very close to the ground.
But the point here is it's not a stable ball of fusion gas. Such a thing is held together by design, neither collapsing nor exploding.
The one dishonestly misrepresenting things here is you.
These experiments demonstrate what is required for fusion.
We know the requirements, and know that it will be quite difficult to create on Earth.
But we also understand that stars can provide those requirements, and even use that to put bounds on the requirements for something to be a star.
There is absolutely nothing to demonstrate that the sun is held together by design.
Instead, it is held together by equilibrium.
Gravity is what caused to start fusing. This increases the pressure, pushing outwards, to stop it collapsing.
If the pressure is too little, then it collapses more, causing fusion to occur at a faster rate, and the pressure increasing, pushing it outwards more.
If the pressure is too great, then it expands, causing fusion to occur at a slower rate.
This process continues until an equilibrium is reached.
There is no need for any magical design in the sun.
We only need to carefully design fusion reactors on Earth, because we don't have the requirements for a star.
Again, we have a coherent model, backed by mountains of evidence. You have "WE DON"T KNOW ANYTHIGN! IT COULD BE MAGIC!!!"