  Planets of 1-4 times Earth's size on orbits shorter than 100 days exist
around 30-50% of all Sun-like stars. In fact, the Solar System is particularly
outstanding in its lack of "hot super-Earths" (or "mini-Neptunes"). These
planets -- or their building blocks -- may have formed on wider orbits and
migrated inward due to interactions with the gaseous protoplanetary disk. Here,
we use a suite of dynamical simulations to show that gas giant planets act as
barriers to the inward migration of super-Earths initially placed on more
distant orbits. Jupiter's early formation may have prevented Uranus and Neptune
(and perhaps Saturn's core) from becoming hot super-Earths. Our model predicts
that the populations of hot super-Earth systems and Jupiter-like planets should
be anti-correlated: gas giants (especially if they form early) should be rare
in systems with many hot super-Earths. Testing this prediction will constitute
a crucial assessment of the validity of the migration hypothesis for the origin
of close-in super-Earths.
