...Either encounter would also leave alien planetoids in our solar system (and some of ours in the alien system) orbiting at a steep angle to the plane in which the planets go around. And so the next step is to search for such objects.
Sedna itself has only a moderately inclined orbit, the astronomers say. A more likely candidate for an extra-solar origin is another icy wanderer, known as 2000 CR105, about half the size of Sedna, discovered out beyond Neptune in 2000. Its orbit is inclined 20 degrees to the planets.
The detection of objects with inclinations of 40 degrees or more, the authors write in Nature, 'would clinch the case for extrasolar objects in the solar system.'
Great. Planetary bodies whipping around in unexpected orbits. The article doesn't say how far out these objects are supposed to be.