Before the onslaught of the extra-Solar planets, the party line was that planets formed at particular radii in the Solar Nebula and essentially spent their lives at around the same distance from the Sun. This position is no longer held by most people. The snowline in our planet forming disk is around 3-4 AU and it was expected that all Jovian planets in extra-Solar planetary systems would be found outside the snowlines of their disks. The discovery of so-many Jupiter-like planets close to their stars, inside the snowlines, suggested that planets likely migrate around their systems over their lifetimes.

223 Kepler