Exoplanet PhD projects

Research projects on offer in our Exoplanet research group.

Detecting and Characterising Giant Planets with Direct Imaging

Beth Biller

Direct imaging will be a vital method to characterize a wide range of exoplanets in the next decades and may eventually determine whether “habitable zone” planets are truly habitable. Deep characterization of giant exoplanet atmospheres now is necessary to develop the expertise for similar studies of Earth-like exoplanets in future decades. The James Webb Space Telescope (JWST) represents a paradigm shift for this field, enabling imaging and spectroscopy of these objects (Teff=500-2000 K) for the first time ever at λ>5μm.  This project will leverage the transformative capabilities of ERIS, a new mid-IR imager for the VLT, and JWST.  There are three potential directions to be explored with this project:

1. The full spectral energy distributions of giant exoplanet atmospheres: Professor Biller is co-PI of the JWST Early Release Science programme 1386, which will, for the first time, directly image exoplanets at λ = 5 – 15 μm.  The ERS data is expected 6 months after launch in October 2021.
2. Weather maps of exoplanets: Variability monitoring probes the 3-d time-resolved structure of exoplanet atmospheres. JWST and ERIS will enable variability searches at λ >2 μm and for exoplanet companions >0.5" from their stars.
3. Confirmation of exoplanet candidates with novel spectral detection techniques: multi-band imaging using carefully selected narrow-band filters can immediately confirm exoplanet candidates.  We plan a high-contrast survey with ERIS' gvAPP coronagraph, to search star-forming regions for young exoplanet companions.

Extending Tests of Substellar Models to Planetary Masses

Trent Dupuy

Substellar models underpin our theoretical understanding of all objects incapable of sustained nuclear fusion – from brown dwarfs to gas-giant planets. The strongest tests of these models require direct, dynamical mass measurements, which are only obtainable from binary systems. The coldest brown dwarfs are our best analogs to extrasolar gas-giant planets, representing the lowest mass products of star formation. Our view of such objects has been transformed over the last few years as new observations have revealed that the solar neighborhood is populated by much colder objects than previously recognized, but they only very rarely appear in binary pairs. As a result, the current sample of masses ends well above the planetary-mass regime (~2–15 Jupiter masses).

This project will exploit a decade's worth of high-precision astrometry obtained from space (HST and Spitzer) and the ground (Keck laser guide star adaptive optics and CFHT) to extend the sample of dynamical masses into the planetary regime. These binaries have been discovered at the extreme limits of existing facilities and thus are the only viable source for dynamical masses in the era of JWST. In addition to the astrometric monitoring data, there is also the opportunity to work on resolved spectroscopic data from HST, the new adaptive optics-fed spectrograph ERIS at VLT, as well as proposing for JWST spectra. Spectroscopy enables tests of ultracool atmosphere models (400–1000 K), and mass measurements break degeneracies between poorly known model parameters, such as those governing cloud formation and fundamental properties like surface gravity. This sample of binary systems will establish the gold standard for studies of ultracool atmospheric physics as the only objects with directly measured spectra and masses.

Under the Astrobiology projects see also:

• True and false signatures of habitability and life on exoplanets -Sean McMahon & Beth Biller