My thesis research aimed to help build on our understanding of the earliest history of our Solar System. How did the planets form? Why do we see them in their current positions? In the last fifteen years, our story of how our Solar System came to be in its present state has altered dramatically - and this is largely due to knowing more about some of the smallest worlds in our planetary system.

The formation of the planets left a population of remnant worlds orbiting on the outer edges of the Solar System, in the vast spaces beyond Neptune. These small objects, no larger than the state of Western Australia, have remained near-undisturbed on their orbits. They offer a snapshot of the earliest times, and their existence places limits on the potential migrations of the giant planets.

The first search for these distant worlds was made by a young astronomer, Clyde Tombaugh, in 1930. His survey discovered Pluto; but it was not until the early 1990s that new surveys with digital cameras discovered more such worlds, and began to show us the abundance and diversity of Pluto's kin.

Our surveys at Siding Spring Observatory aim to complete this emerging picture. The Uppsala telescope observes every night as part of an ongoing program to detect swift-moving near-Earth asteroids. For my PhD, I reprocessed five years of their observations to look for the much slower motion of large, bright trans-Neptunian objects. The dwarf planets have been thoroughly surveyed in the Northern Hemisphere, but no extensive search has yet been completed in the South.

I worked with Brian Schmidt and Paul Francis at RSAA and with Mike Brown at Caltech; here Mike discusses our work.