Preventing stars from eating their young

Researchers have found a mechanism that prevents newly forming giant-planet cores from spiralling in towards their parent stars. The result may explain why planets such as Saturn and Jupiter are where they are today. See Letter p.63 How planets resist inward migration Planetary formation theory predicts that embryonic planets smaller than about five Earth masses will migrate rapidly towards the host star, in which case these embryos would only rarely become giant planets orbiting at Earth's distance from the Sun and beyond. Observations show that giant planets do exist at such distances, in extrasolar planetary systems as well as in our own. Here Benítez-Llambay et al . describe a mechanism that can provide a channel for the formation of giant planets. They find that asymmetries in the temperature rise associated with accreting infalling material produce a force — a 'heating torque' — that counteracts inward migration.