The Population of Earths and super-Earths into the Habitable Zone

The “radius valley” is a feature in the short-period, small exoplanet population in Kepler and K2 data showing an abundance of super-Earths (1-2 R_⊕) and mini-Neptunes (2-3.5 R_⊕), with a relatively scarce population of intermediate-sized planets between the two. By employing updated stellar properties and implementing refined measures of completeness and reliability, we discover that the occurrence of super-Earths over that of mini-Neptunes has a period and stellar mass dependence. This result is explored in the context of atmospheric loss mechanisms. We use these dependencies to extrapolate the occurrence of Earths and super-Earths in the habitable zone of FGK stars. Finally, we discuss our results in the context of upcoming missions’ search for long-period small planets and their dependence on stellar mass.