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.

Planet formation during the earliest stages of star formation

Ken Rice and Alison Young

It’s now becoming clear that planet formation starts during the earliest stages of star formation. Planets are thought to form from the coagulation of solid dust grains, which must gradually grow from less than a micron in size to eventually build a planet.  Specifically, there is increasing evidence for this grain growth occurring when these protostellar systems are very young. During this epoch, the protostellar discs may also have masses comparable to that of the host star and may be susceptible to the growth of a gravitational instability.  This instability will lead to the growth of spiral density waves, which may enhance the local density of solid particles and promote grain growth.   It’s also possible, though, that grain growth starts during the collapse of the molecular cloud core, prior to the formation of a protostellar disc.  This project will use numerical simulations, primarily Smoothed Particle Hydrodynamics (SPH), to simulate the earliest stages of star formation with a particular goal of understanding how this epoch can influence, and aid, the growth of planet-building material.   Initially, this work will focus on understanding processes associated with the earliest stages of star formation.  However, the aim would be to introduce solid particles into these hydrodynamic simulations to study how they evolve and grow.  The project will also involve generating observational signatures of the various processes that can then be compared with observations, in particular those from the Atacama Large Millimetre/sub-millimetre Array (ALMA) which can provide detailed observations of these very young systems.

Hunting for Hidden Objects in the Solar Neighborhood with Gaia Accelerations

Trent Dupuy

The search for faint objects around bright stars, like planets, brown dwarfs, and even white dwarfs, has provided many advances in our understanding of star and planet formation and evolution. In fact, the very existence of very faint stellar-mass objects (that we now know to be white dwarfs) was first proposed in the mid-19th century to explain the apparently curved motion of the stars Sirius and Procyon over centuries of observations. ESA's Gaia spacecraft has dramatically improved the accuracy of such stellar motion measurements, revealing all of the stars in the solar neighbourhood that have curved (accelerating) paths on the sky caused by orbiting companions as small as gas-giant exoplanets. This PhD project will explore the nature of the companions causing the accelerations observed by Gaia. In cases where there is already an orbiting object known from direct imaging, the new acceleration measurements will provide a measurement of their mass (like has been done now for beta Pic b and c, HR 8799 e, and 51 Eri b). In other cases, the acceleration will guide ongoing direct imaging surveys with adaptive optics at some of the world's largest telescopes (VLT, Keck, Subaru) aiming to uncover new discoveries (like HD 33632 Ab). New instruments like ERIS at the VLT will be able to provide detailed spectroscopic characterizations of these companions, enabling tests of elemental abundances and atmospheric chemistry that hold clues as to the origin and evolution of brown dwarfs and giant planets.