Planet compositions from disintegrating exoplanets

Our recent work has focussed on extremely close-in exoplanets which are losing mass as a result of their proximity to their host star. These systems are particularly interesting because they offer the potential to assess their chemical composition by the technique of transmission spectroscopy (e.g. Fossati et al 2010; Haswell et al 2012). This information provides key constraints to models of planet formation and evolution, and helps place our own Solar System in context. Our Hubble Space Telescope observations revealed that mass loss from the extreme hot Jupiter, WASP-12b, feeds a diffuse gas shroud around the planetary system, completely absorbing the starlight at the centres of the MgII h&k lines.
Meanwhile at least two very close-in transiting small disintegrating planets have been discovered in the Kepler database. The best-studied is KIC 1255b, which is a ~0.1 MEarth planet in a 16 hour orbit. The planet is hot enough for direct sublimation of the rocky surface at the sub-stellar point, and a time-variable cloud of dust and metal-rich vapour from KIC 1255b produces periodic transits of varying depth (Rappaport et al 2012). Systems like this can also reveal the planet composition by transmission spectroscopy, but the objects found by the narrow & deep Kepler survey transit apparently faint distant stars, which limits the signal to noise that can be obtained. Fortunately, however, we have shown that a further opportunity to examine the composition of such planets is provided by observing and modelling the dust extinction properties (Bochinski et al 2014). This is particularly exciting as these objects may be the remnant cores of evaporated hot Jupiter planets: consequently we can directly sample the composition of giant planet cores, something not possible even for the Solar System giants.
This project will focus on identifying and characterising disintegrating exoplanets (WASP-12b and KIC 1255b analogues) orbiting around bright, nearby stars. There are data and bespoke software in hand to begin the project, but the student will be expected to develop new software as required and to perform new observations using a variety of telescopes. The Open University Exoplanets Group benefits from the expertise of numerous internationally distinguished planetary scientists who work in the same department.