First author

For Robin Canup, studying the celestial pas de deux of planet and satellite formation is linked to more Earthbound dances. Until six years ago, Canup, who is director of the Southwest Research Institute's Department of Space Studies in Boulder, Colorado, was prima ballerina with the Boulder Ballet. Together with co-author William Ward, she combined an artistic mindset with scientific endeavour to try to understand why the Solar System's gaseous planets and their satellite systems have a nearly constant mass ratio. The results, published on page 834, provide clues on the choreography of planet formation. Canup spoke to Nature about her work — and the link between space science and dance.

What's the relationship between ballet and studying planet and satellite formation?

In many creative endeavours, you have very structured and formal techniques that are the foundations upon which you try to do new things. In ballet, that structure is the classical technique. In space science, it is physics and mathematics. In both science and art, it is important to distil a problem down to its fundamentals as much as possible, while still expressing yourself creatively. The formal rules seem constraining in some respects. But ultimately they are liberating because they provide you with time-tested forms within which to work.

What is the significance of the mass ratio?

We believe the satellites formed in the presence of gas — mainly hydrogen — because the planet was in the end stages of formation. As the planet swept in gas and solid material, a disc formed around it, and the satellites formed within this disc. The gravity of a satellite induces spiral waves in the gas disc, and gravitational interactions between these waves and the satellite cause the satellite's orbit to contract. This effect becomes stronger as a satellite grows, so that the bigger a satellite gets, the faster its orbit decays, implying a maximum satellite size.

How did you model this system?

We developed a numerical simulation that tracks the inflow of solids and gas into orbit around the planet, and followed the growth of satellites, their orbital evolution and their loss due to collision with the planet.

How does your dance background extend to your scientific management style?

Scientists are a lot like artists; each person has their own unique style. So to whatever extent possible, I try to give people the freedom to work in the manner that is best for them. You want to try to create an environment that encourages talented people to do their best creative work.