View larger. | Artist’s concept of the exoplanet called GJ 9827 d, which is either a super-Earth or sub-Neptune world. Astronomers believe it is a steam world, with a lot of water vapor in its hot atmosphere. A new study focuses on how to understand steam world exoplanets better. They have hot, steamy atmospheres and layers of exotic supercritical water. Image via NASA/ ESA/ Leah Hustak (STScI)/ Ralf Crawford (STScI)/ University of Montreal.
