Until the mid-1990s, astronomers had never found conclusive evidence for planets outside our own solar system. But improving technology made it possible to begin finding such planets, and more than 2,000 had been discovered by mid-2012. The existing technology makes it easier to find large planets than small ones and easier to find planets that orbit close to their stars than planets that orbit far from their stars. According to the leading theory of solar system formation, large planets should form far from their stars, not close by. But large planets in close orbits are quite common among the planets discovered to date. Does this mean there is something wrong with the leading theory of solar system formation?