Can the sun suddenly go out?

Answer

I will already answer your questions about the sun.
There is a wonderfully stable equilibrium in the sun that will indeed last for another 5 billion years. One player is gravity (which wants to make the sun contract). But because of that contraction, pressure and temperature rise, making it so hot in the core that nuclear fusion occurs. This energy production ensures that the pressure course and the gravitation keep each other in balance.
If you were to compress the sun’s core a little more, the pressure and temperature would rise, causing it to expand again, undoing the contraction. In the other direction, if the core expanded slightly, pressure and temperature would drop, and gravity would no longer be fully compensated by the pressure gradient. The core would therefore contract slightly again until equilibrium is restored.
This equilibrium is thus stable and it will last until all the hydrogen in the core has been converted into helium. Then gravity gains the upper hand, and the core will contract. But precisely because of this, the temperature rises so that at a temperature of approximately 100 million degrees helium combustion starts, and a short period of stability occurs again.
If you want to know more about this, maybe read something about stellar evolution.

The Earth revolves around the sun, and the sun, which is one of the galaxy’s 100 billion stars, orbits the center of the Milky Way once every 250 million years. So the sun is constantly falling but has enough speed to stay in that orbit, just as the earth is constantly falling but has enough speed to stay in its elliptical orbit around the sun. This too is a stable equilibrium. The galaxy also moves as a whole in the gravitational field generated by the other galaxies and larger structures in the Universe.

Did you know that there is an umbrella association of amateur astronomers in Flanders?
Their website is www.vvs.be