Using advanced new simulations, a team of astronomers in the U.S. has developed a promising new theory for how giant, gaseous exoplanets migrate into stiflingly close orbits around their host stars. Led by J. J. Zanazzi at The Pennsylvania State University, the team showed how both massive "hot Jupiters" and smaller, Neptune-sized planets could migrate from distant, elliptical orbits as they release energy via dramatic shock waves in their outer atmospheres. Their results have been published in The Astrophysical Journal.