Planetary compositions from disrupting exoplanets

Astronomy Unit Seminars
Dr Carole Haswell (Open U.)
Guillem Anglada
September 24th, 2014 at 14:30
GO Jones Room 610

Thousands of exoplanets have been discovered in the last 20 years, offering
us the opportunity to place our own Solar System in its Galactic context. This
new field of comparative planetology is limited by the rather sparse
information we have on the vast majority of the known exoplanets. The exoplanets
with orbits which happen to be aligned so that they transit across the face of
their host star are particularly valuable: for these we are able to directly
measure their size and mass. For exoplanets transiting nearby stars, high signal
to noise observations can empirically determine the presence of various chemical
species through differential spectroscopic techniques. We studied an extremely
close-in hot Jupiter exoplanet, WASP-12b, detecting absorption from dozens of
species in the extended exosphere of the planet. Surprisingly, we also
discovered that the entire planetary system is shrouded in diffuse gas lost from the
heavily irradiated planet. WASP-12's gas shroud produces noticable absorption in the
strongest lines of abundant species: we first noted it in Mg II h&k, and found a
similar signature in the Ca II H&K lines. Meanwhile, the Kepler mission has
revealed evidence for dozens of small rocky bodies orbiting their host stars with
sub-day periods. I will review the background material outlined above and show how
this allows us to identify some very interesting close-in exoplanetary
bodies orbiting nearby stars. Once identified, these systems will permit exquisite
quality observations revealing their compositions in unprecedented detail.