Astronomers may finally have glimpsed a key step in the construction of a planet.
Both theory and observations suggest that the doughnut-shape disks of gas and dust that surround many newborn stars are the spawning grounds for planets. The Hubble Space Telescope has spied many such protoplanetary disks. Since 1995, astronomers have found evidence of more than 60 fully formed planets as massive as Jupiter orbiting nearby stars.
Yet astronomers had yet to spy a crucial intermediate step: To make a planet, the fine dust grains within a disk must coalesce into larger particles. Now, researchers say they've seen just that.