Vol. 622
In section 10. Planetary systems

Two new free-floating or wide-orbit planets from microlensing

Planet-formation theories predict the existence of both free-floating planets, which a strong dynamical interaction with additional massive bodies unbinds from their parent star, and of planets on very wide orbits, which remain just bound to this parent star. Such planets emit very little light, but can be detected when they happen to gravitationally lense a background star. The authors present two ultrashort strong lensing events which are best interpreted as being caused by planets that are either free-floating or on wide orbits. These two detections suggest, though with large statistical errorbars, that free-floating and wide-orbit planets are more common than stars in our Galaxy.