# Gravitational forces in protoplanetary disks may push super-Earths close to their stars

Penn State-led astronomers found that as planets form out of the chaotic churn of gravitational, hydrodynamic — or, drag — and magnetic forces and collisions within the dusty, gaseous protoplanetary disk that surrounds a star as a planetary system starts to form, the orbits of these planets eventually get in synch, causing them to slide — follow the leader-style — toward the star.