A rogue planet is a free-floating world that drifts through the galaxy bound to no star, either ejected from a planetary system or formed on its own. Because they emit almost no light, they are detected mainly through gravitational microlensing, when one briefly magnifies a background star. Estimates suggest rogue planets may rival or outnumber the stars, and the James Webb Space Telescope has spotted Jupiter-mass free-floaters drifting in the Orion Nebula.