High-Inclination Centaur Asteroids Came from Interstellar Space: Study
http://www.sci-news.com/astronomy/centaurs-interstellar-space-08369.html
“At least 17 high-inclination Centaurs and two trans-Neptunian objects were captured by the Solar System from the interstellar medium, according to a new study published in the Monthly Notices of the Royal Astronomical Society.
“Due to giant planets’ perturbations, these objects have transient orbits with typical lifetimes of a few million years. If a Centaur orbit is integrated forward or backward in time, it will invariably either hit the Sun, the planets, or be ejected from the Solar System.
“Centaurs appear to be intermediate between asteroids and comets, as any Centaur coming close enough to the Sun is expected to show cometary activity.”