No Stupid Questions

This sounds like an XKCD what-if that ends with an explosion that could deafen god himself.

Like, if it just pops into existence, "static" relative to the sun, it'd all slowly fall into the sun. The solar system is ehhh 100 AU wide, atmospheric density's about 1 kg per cubic meter, 1 AU is ~1.5e11 m... volume of a sphere is 4/3 * pi * r^3... that'd be 4.5e39 kg of gases, or basically 500,000,000 times the current mass of the sun. So, at a wild guess, probably enough to form a black hole? But it cannot be good for the inner solar system either way. Especially not if we work out how an Earth-shaped column of that gas falls into the sun with Earth in the way.

(Edit: Sagittarius A* is only 4e6 solar masses. 5e8 is borderline supermassive. Things would go poorly.)

If it spins instead - if it's all playing nicely with the orbits of each planet and the general flow of the asteroid belt - we probably don't all die fantastically. At least not for a while. We can assume it'd be a plane instead of a sphere, maybe 1 AU thick, as if the sun had rings. I don't think it'd just diffuse out into the cosmos? Once all that mass is orbiting, you'd only lose the weird exceptional atoms that reach the edge with a bunch of energy and then don't hit anything for a zillion miles. That also happens at the top of Earth's atmosphere, and we've got gravity keeping it in check. So let's just hand-wave that this situation lasts, like, at all.

Those bands in the rings will experience friction. Any speed differential has consequences, and I do not want to think about the computation requirements for that kind of fluid simulation. I think at worst they'd separate. They can't all take the same angular velocity because that's not how orbits work. They might fuck up the planets moving through them? Like, I don't know much about astrophysics, but when a planet has rings it's not because things went well for the satellites in that range.

Actually that highlights how the planets would have the same issue as the sun, if a bunch of mass magically appeared overhead, in their reference frame: it'd fall. Air doesn't weigh much, but when you hand-wave an entire gazillion miles of it, that adds up. We'd have problems well before the atmosphere started to outpace the entire solid mass of Earth.

If this atmosphere orbits each planet, the way the whole shebang orbits the sun - you're back to speed differentials. Just thinking locally: there'd be different spin for air that refuses to fall toward Earth, and air that refuses to fall toward the moon, and somewhere in the middle those two streams would meet. Or - at best! - they wouldn't quite meet. The gaps would separate themselves. You could maybe do a cool sci-fi setting with that, but your space 747 would need to zoop clean out of Earth's sky-ocean and catch the moon's.

Oh. And I don't think sunlight would be visible through one hundred and fifty million kilometers of atmosphere. At least, until the sun slurped up a couple yottatons of it, at which point we'd have whole new problems.