What if...

[xXRandomUserXx]

So I've been wondering what would happen if the periapsis of an orbit around -say a black hole- was so near the point of gravity that the speed nearing periapsis would exceed have to exceed C to complete an orbit. I couldn't find anything about it online. That may be because of I didn't do much research or the simple fact that I don't have physics in school and the question above makes no sense at all.

[The Stinger]

The orbit would decline the closer you would get to the periapsis and you would get sucked in.

[Kerbface]

I don't understand quantum physics that well but as far as I understand, that would just not be an orbit. As the object got closer to the speed of light it's mass would increase exponentially and it would be sucked in. Maybe?

[xXRandomUserXx]

But i mean would it just stop accelerating one it hits the speed of light©?

[Brotoro]

When using Newtonian physics (where all closed orbits are ellipses) you could get cases where the speed at periapsis would have to exceed the speed of light in order for a particle to complete its elliptical orbit. BUT, if you are close enough to a big enough mass for this to happen, Newtonian physics no longer gives you answers that match what we observe happening in our universe -- you have to use Einstein's General Theory of Relativity to properly describe gravity in that situation, and the results show that no object will ever exceed the speed of light.

[Sof]

If your pereapsis has to have a speed above C, then you've crossed the event horizon and are now doomed.

[nhnifong]

something like this I suppose

[K^2]

But i mean would it just stop accelerating one it hits the speed of light©?

The fact that gravity doesn't behave like a force anymore at this point. Objects move through space-time at a constant speed. The speed of light. What changes is how much of that is along spatial directions. Because gravity is properly described as space-time curvature, the maximum local velocity will always be the speed of light.

By the way, you can exceed speed of light when passing a rotating black hole. Your local speed will still be limited to c, but you can be moving FTL relative to remote objects due to frame dragging.