Microlensing events indicate that super-Earth exoplanets are common in Jupiter-like orbits

Exoplanets classified as super-Earths are commonly observed on short
period orbits, close to their host stars, but their abundance on wider
orbits is poorly constrained. Gravitational microlensing is sensitive to
exoplanets on wide orbits. We observed the microlensing event
OGLE-2016-BLG-0007, which indicates an exoplanet with a planet-to-star
mass ratio roughly double the Earth- Sun mass-ratio, on an orbit longer
than Saturn’s. We combine this event with a larger sample from a
microlensing survey to determine the distribution of mass ratios for
planets on wide orbits. We infer there are ~0.35 super-Earth planets per
star on Jupiter-like orbits. The observations are most consistent with a
bimodal distribution, with separate peaks for super-Earths and Jupiters.
We suggest this reflects differences their formation processes.