Neptune's Internal Heat Remains Mysterious Despite Voyager Data

Nearly three billion miles from the Sun, Neptune burns with a warmth that sunlight alone could never explain — radiating 2.61 times more energy than it receives, a quiet thermodynamic riddle that has endured since Voyager 2's fleeting 1989 encounter. Scientists have proposed primordial heat, radioactive decay, and diamond precipitation in the deep interior, yet no single theory closes the planet's energy account. The mystery is deepened by Neptune's near-twin Uranus, which suppresses most of its own internal heat through mechanisms still poorly understood. What Neptune holds in its depths rema