What do you mean by adjacent? How much distance between the baryonic center (of mass) between the two systems? If there are two solar systems with multiple planets, not binary type, then I do not think a planet is chucked from one at will and goes to another and vice versa. For a binary set up, it is quite likely that a planet may be appearing to be closer to star A and may be at some other time closer to star B. If you can call this as exchange.
If the conditions are right, it could happen....In fact a planet could be tossed out of a solar system to wander alone: Smae applies to BH's, if conditions are right.
Non-binary stars could end up crossing paths so close as to destroy the stability of the orbits of their respective planets, with the result that a planet could end up orbiting the different star. Not sure it would be particularly circular, though - likely highly elliptical. Depending upon the relative velocities, planets could also get thrown out of the gravitational influence of both stars.
A transient planetary alignment that leads to an acceleration of one planet towards one or more others, such that it gains a speed > escape velocity of the solar system the planet belongs to. This seems to be a fairly well-known scenario in orbital mechanics and some have proposed that planetary ejection may even have taken place at some point in the evolution of our own solar system, for example as described here: https://astronomynow.com/2015/11/03...t-out-of-the-solarsystem-4-billion-years-ago/
These are catastrophic events, no doubt if two gravitationally bound systems with multiple objects come closer than anything can happen, and that cannot be termed as exchange. I think OP was more concerned with the 'exchange', inquiring about some kind of smooth transition.
I have no opinion or expertise on this but you can research it easily for yourself on the web, I think.
I cannot comment about post collision scenario. Looking at the conservation laws, this cannot be termed as impossible.
Although I think it is unlikely that the body came from outside our solar system, let alone another solar system. More likely it was a remnant of the protplanetary swarm of our own SS. It's kind of like coming across an oasis in the desert and asking from whence the coconuts came from which these palm trees grew? Is it likely coconuts from the nearby (sparsely-palmed) desert? Or coconuts from another oasis a hundred miles away? Or is it likely to be coconuts from this oasis? Please Register or Log in to view the hidden image!
Absolutely! I did not mean to imply that the body was not from the same accretion disc that formed the solar system.
Yeah. But I think Tim does (or will) mean to imply that. I suspect Tim has gotten an idea (from God knows where) that the Moon was created by a collision from a body outside our solar system, and is now looking to cherry-pick evidence that might back it up. This is an anti-pattern in science. But I could be wrong about Tim's intent.
Where gravitational interactions are such, that a sort of "gravity sling shot" or "gravity assist" move is initiated, as is often performed with many space probes heading to the outer planets. http://www.mathpages.com/home/kmath114/kmath114.htm