Lonely wanderers not uncommon

In my upcoming novel “Andromeda: The Encounter,” an Earth-sized planet is wandering lonely through space. Planets far from any star – how common are they? Apparently, this is not an uncommon phenomenon. Star systems can become dynamically unstable and eject single planets. This could have happened to our solar system in early times. That it is a normal sight is also shown by a research work of British scientists. They have discovered evidence of a mysterious population of such free-floating plan...