A bizarre, lemon-shaped planet that may contain diamonds at its core is challenging theories about planet formation. Scientists using the James Webb Space Telescope have uncovered “an absolute surprise”—a rare type of exoplanet with an atmospheric composition unlike any ever seen before. This Jupiter-mass world, which orbits a pulsar, appears to have an exotic helium-and-carbon-dominated atmosphere. Soot clouds likely float through the air, and deep within the planet these carbon clouds can cond