GJ 1214 b orbits a cool red dwarf M-type star 48 light-years from Earth, a sub-Neptune measuring 2.7 × Earth in radius with a mass of 8.41 Earth masses. It completes its orbit every 1.58 days at 0.015 AU, far inside the habitable zone and too warm for surface oceans. A thick haze has long veiled its skies, later shown to be a metal-rich, aerosol-heavy envelope. As the nearby template for the galaxy’s most common planet size, it bridges rocky worlds and ice giants. It endures in the Galactic Codex as the archetypal mini-Neptune, a ledger of hidden skies around diminutive stars.
