Why are the sub-Neptunes so different?

Researchers have studied in detail the intermediate-class planets, which are called sub-Neptunes, meaning they have masses greater than Earth’s but less than Neptune’s. They, for unknown reasons, are of two kinds, and in sorting out what that reason is, scientists have unexpectedly learned something new about the evolution of star systems. Sub-Neptunes An international team of scientists recently published a study that was able to explain one surprising feature of sub-Neptunes. These exoplanets, which have masses greater than Earth’s but …