Professor Joachim Wambsganss of the University of Heidelberg in Germany, who reviewed the study for Nature, said this was the "most plausible theory".

The isolated planets, however, may not have formed around a parent star at all, points out Joachim Wambsganss, with the University of Heidelberg in Germany.

University of Heidelberg astronomer Joachim Wambsganss, who was not involved in the research, said more studies will be needed to confirm that the new planets are indeed drifters.