Pebbles from Heaven: Tracking planets in the making

Recording radio waves from the region around a young star, astronomers have for the first time documented a key step in the rocky road to planethood: making pebbles. The standard recipe for planet formation starts with a disk of gas, dust, and ice swirling around a newborn star. Particles within the disk coalesce into nuggets and then ever-larger clumps, which over several million years grow into a planet.