A young evolving planetary system

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...