Weird worlds

摘要

There was a time when Stephane Udry and his fellow astronomers thought they understood planets. So when they began to find alien worlds circling stars outside our solar system in the 1990s, they presumed they would see clones of the Earth and its siblings emerging from the mist: chilly Jupiters and icy Neptunes far out from a star, with hot, rocky Mercuries closer in.