Astronomers think planets can exist in orbits far from their star, and propose a two-step process: interactions with the star or inner planets kick it out of the inner system, and then a passing star stabilizes the orbit to keep it bound. Such a scenario could explain the hypothesized ‘Planet Nine’ in our solar system. Astronomers has now confirmed that one binary star system, HD 106906, has a planet in a bound, highly eccentric orbit.
