A Solar System in a Grain of Sand

摘要

It takes only about three million years. That's the gestation period of a solar system: three million years for a star to form from an immense cloud of gas that spirals inward, leaving behind the molecules of silicates and metals that will coalesce into planets. That may sound like a long time, but building the foundation of a solar system is a big job; scientists have been trying to understand why it doesn't take longer than three million years. Last November astronomers announced that they have found evidence to support one explanation of how this process was helped along by analyzing a meteorite that is older than the planets themselves.