Located throughout the universe, there are billions — possibly even trillions — of exoplanets orbiting around stars of varying shapes, sizes, colors, and more. Like the stars they orbit, exoplanets also come in many different shapes, sizes, and colors, with scientists classifying exoplanets into one of four groups: gas giants, super-Earths, sub-Neptunes, and terrestrial.
Interestingly, among the 5,000+ exoplanets that have been discovered and cataloged by NASA, ESA, and other agencies, there is a strange absence of exoplanets whose sizes are between 1.5 and two times the size of Earth (between super-Earths and sub-Neptunes). In a new study using data from NASA’s now-retired Kepler Space Telescope, scientists may have found evidence for why this size gap exists — the cores of the exoplanets are pushing away their atmospheres from the inside out.