The science of extra-solar planets is one of the most rapidly changing areas of astrophysics. A combination of ground-based surveys and dedicated space missions has resulted in 550-plus planets being detected, and over 1200 that await confirmation – since 1995, the number of planets known has increased by ~ two orders of magnitude. NASA’s Kepler mission has opened up the possibility of discovering Earth-like planets in the habitable zone around some of the 100,000 stars it is surveying during its 3 to 4-year lifetime. The new Gaia mission is expected to discover thousands of new planets around stars within 200 parsecs of the Sun. Yet among the exoplanets detected or proposed, so far there is actually little resemblance to the morphology of the Solar System.
So now the key challenge is moving on from discovery, important though that remains, to characterisation: what are these planets actually like, and why are they as they are?
To answer those questions requires a combination of skills and expertise that range from Solar System science to statistical astrophysics, from ground-based observations to spacecraft measurements, and from atmospheric modelling to instrument building.