Scientists have found some planets may migrate toward the hearts of their planetary systems early on in their lives, possibly explaining the lack of planets we see that are around twice the width of Earth.
Over the years, scientists have managed to observe many exoplanets that are either smaller or larger than Earth, but planets precisely between 1.6 and 2.2 times the size of our world are relatively scarce. In particular, exoplanets defined as super-Earths or mini-Neptunes appear to be missing in space. They're classified as such if they're slightly larger than twice the size of our planet, but still smaller than the ice giant Neptune.
