A young evolving planetary system
DOI: 10.1063/1.4796826
Has been seen. A star much like our Sun when it was only 3 million years old has been winking at astronomers from a distance of about 2400 light years for the past five years. Every 48.36 days, the star suddenly dims to a small percentage of its normal brightness for about 18 days. The duration and depth of these periodic occultations, discovered by William Herbst and his colleagues at Wesleyan University in Connecticut, had not been seen before. Eighteen days is much too long for occultation by a lone planet in a 48-day orbit. The observations’ most likely explanation, put forth by Herbst at a meeting at the Carnegie Institution of Washington in June, is that a collection of dust grains, rocks, and perhaps asteroids is strung out in a clumpy arc of an orbiting circumstellar disk, with a larger object like a proto-planet shepherding the material. Now, with a worldwide collaboration watching the star continually, the Wesleyan group has found evidence that the orbital period is, in fact, 96.72 days: The star is being occulted by two separate clumpy regions on opposite sides of the disk. Theoretical models indicate that a single shepherding object could account for both clumps. The 97-day period indicates that the ring-like disk is about as far away from the star as Mercury is from the Sun. The collaboration has also seen the system changing slightly on a scale of months and years, thus tantalizing astronomers with the prospect of viewing planetary evolution in real time. (
