Astronomers have discovered clear skies and steamy water vapor on a planet known as HAT-P-11b - outside our solar system.
HAT-P-11b
is about the size of Neptune, making it the smallest exoplanet ever on which water vapor has been detected. HAT-P-11b is a so-called exo-Neptune, a Neptune-sized planet that orbits another star. It is located 120 light-years away in the constellation of Cygnus (The Swan). Unlike Neptune, this planet orbits closer to its star, making one lap roughly every five days. It is a warm world thought to have a rocky core, a mantle of fluid and ice, and a thick gaseous atmosphere. Not much else was known about the composition of the planet, or other exo-Neptunes like it, until now.