Astronomers have measured the mass and distance of a rogue planet, drifting alone through the Milky Way, for the first time. Detected via gravitational microlensing using ground-based telescopes and the Gaia spacecraft, the planet is approximately 10,000 light-years away and weighs about one-fifth of Jupiter. This discovery highlights the effectiveness of combined space and ground observations in finding isolated celestial bodies and may inform future telescope missions.