An article to be published in “The Astronomical Journal” reports a study on three gas exoplanets discovered in the Kepler 51 system belonging to a rare type that has a very low density even by the standards of these planets. A team of researchers led by Jessica Libby-Roberts, a graduate student at the University of Colorado, Boulder, used the Hubble Space Telescope to study those three exoplanets confirming their density so low as to deserve nicknames such as “cotton candy planets” or “super puffs”. This study suggests that they’re quickly losing mass so in the distant future they could turn into mini-Neptunes, a much more common category.