Missing planets twice Earth’s size may point to migrating worlds
Exoplanets can come in a variety of sizes and masses. If you were to plot on a graph how many planets of each size astronomers have discovered, you’d find two peaks: one at 1.4 times Earth’s radius, and another at 2.4 times Earth’s radius. Between them is a dip or valley, at around 1.8 times the radius of Earth, signifying the relative scarcity of planets of that size.