If something were ejected from the solar system (like a planet for example), where exactly would it end up? Where does it go?

Question

I have been reading about space and whatnot, and came across an article about a “lost planet” that Jupiter kicked out of the solar system therefore ejecting it, and it made me wonder where it went. Does it just keep falling? Or is there a particular place in the universe that it may have ended up by now?

Short answer: orbiting within our galaxy nearby our solar system. The subjects of galactic anatomy, orbital mechanics and escape trajectories are very complex and broad. A full answer of where an ejected planet would end up would depend highly on the initial orbit, the strength/direction of the 'kick' and a multitude of other factors. — Jack, Jun 10 '18 at 12:01
If you'd like a to gain a good understanding of how this works, may I suggest narrowing your question a bit to a particular example a 'lost planet' so answers have a good starting point. Also I'd suggest heading over to Astronomy SE where questions of this nature are more common. And welcome to Space SE! — Jack, Jun 10 '18 at 12:08

peterh · Answer 1 · 2018-06-10T22:42:39.360

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Stars are orbiting the center of our the Galaxy on roughly¹ circular orbit bound by exactly the same mechanics, which holds the Solar System together: the centipetal force and the gravitational force.

Anything ejected from the Solar System goes into such an orbit, typically into a circular orbit not very different as our Solar System does.

This orbit has the period of around 160million years, due to the initial divergence later it might move very far away from us.

¹_{See comments.}

edited Jun 10 '18 at 22:42

answered Jun 10 '18 at 14:23

peterh

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Galactic orbits are actually quite different, because the mass of the galaxy is not very concentrated at the center. There are different kinds of orbital families and the only similarity that one of them shares with the solar system is that it looks circular when viewed from the top. – AtmosphericPrisonEscape Jun 10 '18 at 22:36
@AtmosphericPrisonEscape Thanks, I know. As far I know that there is also an oscillation perpendicular to the galactic plane, maybe with a 40million year long cycle. I didn't write these because the question didn't seem asking for so deep details, although it would be possible to extend the answer with them. – peterh Jun 10 '18 at 22:40

score 1 · Answer 2 · answered Jun 10 '18 at 15:06

Where it would end up would depend on how fast it was going when it was ejected. It obviously attained solar escape velocity (perhaps 60km/s). To escape the galaxy, it would have to be accelerated to some 490km/s or more, which seems a rather unlikely event. So, while it may no longer be gravitationally bound to our solar system, it would remain gravitationally bound to the galaxy, so would be, like the solar system, in an orbital path around the galactic center of mass.

If something were ejected from the solar system (like a planet for example), where exactly would it end up? Where does it go?

2 Answers2