Neptune-like Exoplanets

Ice giants with thick atmospheres of hydrogen, helium, and volatile compounds like water and ammonia.

Neptune-like exoplanets have radii between 2.0 and 6.0 Earth radii (or masses between 10 and 100 Earth masses). Similar to Neptune and Uranus in our solar system, these worlds have substantial atmospheres rich in hydrogen and helium, with interiors that may contain water, ammonia, and methane ices under extreme pressure. Some Neptune-like planets orbit very close to their stars, creating a subclass known as "hot Neptunes" with temperatures exceeding 1,000 K. The "Neptune desert", a scarcity of Neptune-sized planets in very short-period orbits, remains one of the puzzles of exoplanet science.