There may be more rogue planets drifting through space in the Milky Way than there are actual stars. This is how they found one of them.
If a solar system is a family, then some planets leave home early. Whether they want to or not. Once they’ve left the gravitational embrace of their family, they’re pretty much destined to drift through interstellar space forever, unbound to any star.
Astronomers like to call these drifters “rogue planets,” and they’re getting better at finding them. A team of astronomers have found one of these drifting rogues that’s about the same mass as Mars or Earth.
Finding something in deep space that emits no light of its own is extremely challenging. But two organizations are doing just that. They’re the OGLE (Optical Gravitational Lensing Experiment) collaboration and the KMTN (Korean Microlensing Telescope Network) collaboration.