rationalskepticism.org

Friction can be ignored. It has no notable effect on the Earth's orbit over thousands of years. The scenario described requires the solar system capture the incoming planet. This can theoretically occur in a more than two body system (the reverse process of objects getting ejected) without an actual inelastic collision. The combined Sun - Jupiter system could capture and or eject objects which pass close enough to Jupiter on the right trajectory. The mechanics of it is utilised by spacecraft gravity assists to either get to more distant planets or in the case of the pioneer and voyager craft ultimately eject them from the solar system altogether. (One way you can guess that some of the gas giant moons are captured objects is that to get the reverse of a gravity assist they would end up in retrograde orbits). The chances of a planet sized object initially on a hyperbolic orbit being captured by the solar system without a direct hit on something on the first (and most likely only pass) sounds rather implausible to me. Much more dangerous and probable would be the close approach of another star. IIRC at least one relatively low mass star will pass by less than a light year from the solar system in the next few million years. If one passed close enough to disturb the Oort cloud we could be in trouble.

Oh yeah Gliese 710