When astronomers started discovering planets around other stars, one of the biggest surprises was the discovery of many Jupiter-sized gas-giant planets orbiting extremely close to their parent stars. Later, as instruments got better, we started to discover massive rocky planets that were also very close — in fact, even more of them than the “close-in” gas giants! Sky & Telescope magazine recently summarized work by CIERA Postdoctoral Fellow Francesca Valsecchi, Professor Fred Rasio, and Lindheimer Fellow Jason Steffen, which examines these close-in rocky planets and connects them to their gas-giant cousins. They show that such close-in rocky planets could be the aftermath of gas-giant planets losing mass to their central star.