The story of the birth of our solar system has been worn smooth through years of retelling. It starts billions of years ago with a black, slowly spinning cloud of gas and dust. The cloud collapses, forming our sun at its heart. In time, the eight planets, along with lesser worlds such as Pluto, emerge from leftover gas and debris swirling about our star. This system of sun and planets has been whirling through space ever since, its motions as accurate and predictable as clockwork.