The Hunt for Rogue Planets: The Galaxy May Hold a Trillion Wandering, Sunless Worlds. So How Do We Find Them?

ON 29 OCTOBER 2020, astronomer Przemek Mróz from the University of Warsaw and an international group of collaborators reported a peculiar flicker of light originating from halfway across our galaxy. The signal, designated OGLE-2016-BLG-1928, was extremely subtle. It caused a single star to brighten and dim by about 20 percent over a 6-hour period, just once, never repeated. But the implication of that little flicker was huge: It was the first credible sighting of an Earth-size “rogue planet,” a world untethered to any star, floating freely between the stars.