The discovery and exploration of the trans-Neptunian region

First predicted qualitatively in the 1940s, quantitatively in the 1980s and finally discovered in the 1990s, the planetesimals beyond Neptune provide a fossil record of the early history of the solar system. A decade of observations have shown that the region is far more complicated, both dynamically and compositionally, than originally suspected and it continues to challenge both observers and modellers who attempt to understand it. This region of space provides an observational link between evolved planetary systems like the solar system and the disks of material recently detected around other nearby Sun-like stars. To cite this article: J.K. Davies, C. R. Physique 4 (2003).