Astronomers have long thought of super-Earths as the rocky cores of mini-Neptunes whose gassy atmospheres had blown away, but a new study challenges that theory.
Mini-Neptunes and super-Earths up to four times the size of our own are the most common exoplanets orbiting stars beyond our solar system.
In the new study in the
Astrophysical Journal, astronomers show that some of these exoplanets never had gaseous atmospheres to begin with, shedding new light on their mysterious origins.
From observations, we know about 30% to 50% of host stars have one or the other, and the two populations appear in about equal proportion. But where did they come from?