Unknown unknowns

Astronomers have discovered evidence of "up to ten" planets floating alone in the dark of space, away from the light of a star.The discovery indicates there are many more free-floating Jupiter-mass planets that can't be seen. But wait, that's not all: "The team estimates there are about twice as many of them as stars. In addition, these worlds are thought to be at least as common as planets that orbit stars. This would add up to hundreds of billions of lone planets in our Milky Way galaxy alone."