If the center of our galaxy is tens thousands of light years away and hypothetically collapsed on itself, we wouldn’t know for tens of thousands of years. So then in the meantime, what exactly is our solar system orbiting, if it no longer exists?

Question

I am genuinely curious about this. I *kind of* understand that gravity, like light, moves at the speed of light (right?). So then would our solar system, and millions of other star systems, just continue orbiting what USED to be the super massive black hole in the center of our galaxy, if said black hole just suddenly (hypothetically) collapsed/vanished? How does that not violate the laws of physics?

Furthermore – let’s say a star… a hundred light years away went supernova. We’re still receiving it’s light for a hundred years right? It would just look totally normal to us in the sky, for the next hundred years. Well let’s say that supernova was so awesomely powerful as to truly push our planet out of orbit from our sun. What happens first? Does that star’s supernova explosion light up in the sky, or does that impact from this supernova hit us and cause catastrophic damage? What’s faster – the impact or the supernova?

I really want to understand distance/time better as it relates to astrophysics, I just can’t comprehend the insane distance and the deltas between distance + time = what we experience on earth. It’s truly humbling.

In: Physics

Answer 1

The supermassive black hole is relatively inconsequential on a galactic scale. We (and by and large the rest of the galaxy) are orbiting the *center of mass* of the galaxy itself. That is to say, not an object at all, but a point in space as a result of the interactions of all the stuff in the galaxy as a whole. We definitely do not orbit the black hole, and while it is near this center of mass, it is not the center of mass nor the specific cause of it.

We expect a change that substantially altered the location of the center of mass would propagate outwards at the speed of light. There’s no known mechanism by which it could travel faster. So if something “deleted” the other half of the galaxy, the gravitational effects (flinging the galaxy apart?) would work their way outwards at lightspeed.

>Does that star’s supernova explosion light up in the sky, or does that impact from this supernova hit us and cause catastrophic damage?

I would question here, “impact” of what? In any (remotely) likely scenario where a supernova damages us, the impact itself is going to be of *light*, which can still be quite damaging. If you mean light versus any physical matter of the supernova, the light would reach us well in advance.