Exoplanet PhD projects

Research projects on offer in our Exoplanet research group.

Detecting and Characterising Giant Planets with Direct Imaging

Prof 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 (T_eff = 500-2000 K) for the first time ever at λ > 5 μm. 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: JWST uniquely enables long wavelength observations of directly imaged exoplanets.  Combining with shorter wavelength datasets covers the full spectral energy distribution of these planets, yielding highly accurate bolometric luminosities. Combining bolometric luminosities and carefully measured ages for these systems provides new, accurate estimates of the masses and effective temperatures of these planets.

2) Weather maps of exoplanets: Variability monitoring probes the 3-d time-resolved structure of exoplanet atmospheres. JWST and ERIS enable variability searches at λ > 2 μm and for exoplanet companions >0.5" from their stars.

3) Surveys to directly detect lower mass and cooler exoplanets: Multiple surveys are underway to search for and directly image a wider range of young exoplanet companions, including SURVEY 6005 with JWST and an ongoing survey of the < 10 Myr eps Cha young moving group. The extreme sensitivity of JWST provides sensitivity down to young analogues of Saturn, while ERIS yields sensitivity to overlooked young exoplanet companions in nearby star-forming regions.

Characterising hot and cold exocomets in the Beta Pictoris system during the PLATO mission

Dr Cyrielle Opitom, Prof Colin Snodgrass, and Dr Matthew Kenworthy (Leiden)

While thousands of exoplanets have now been detected, only a small fraction of these exoplanetary systems have shown signatures of the presence of exocomets. One of the first fields that will be observed continuously after PLATO mission is launched contains the young star Beta Pictoris. Spectroscopic observations in the optical at the Calcium H and K lines show the presence of transient blue shifted absorption, attributed to exocomets falling towards the star with periastron distances of a few stellar radii. Previous photometric observations with TESS have shown the presence of over twenty exocomets in broadband light thought to be due to slower moving comets at a few astronomical units from the star. Due to the nature of these observations, no ground based spectroscopic follow-up of these transits was possible.

To characterise these exocomets, we need to carry out a spectroscopic monitoring campaign during the PLATO observations such that any broadband transits due to exocomets can be matched up with simultaneous spectroscopic observations from the ground. This project will focus on the set-up of dedicated spectrographs and/or small observatories in time for the start of the PLATO observations in 2027. It will be shared between Leiden and Edinburgh to take advantage of the respective exocomet and instrumentation expertise in the two institutes.

Modelling atmospheric chemistry and dynamics on a Venus-like exoplanet

Prof Paul Palmer, Prof Ken Rice, and Dr Alistair Glasse

There are striking similarities between Earth and Venus. They are nearly the same size and density, yet one evolved to support life and the other evolved into an inhospitable planet that is the hottest in our Solar System. There are many fundamental gaps in our understanding of Venus, but this PhD will focus on the evolution of its atmospheric composition. We will use recent discoveries of Venus-like exoplanets, e.g., Gliese 12 b discovered in 2024, to provide important insights into how Venus evolved into its current form. 

In this project, we will use a planetary climate model to describe plausible environmental conditions on a Venus-like exoplanet, nominally Gliese 12 b. Gliese 12 b is similar in size to Venus and is orbiting an M-type star with a period of 12.8 days. Despite the proximity of the planet to its host star, it receives a similar amount of radiation to Venus. Our initial chemical network will be informed by established Venusian atmospheric chemistry networks that include gas-phase and heterogenous chemistry, accounting for refinements as they become available. We will use a range of initial environmental conditions, informed by literature, to explore how they influence the evolution of atmospheric chemistry and dynamics, including the theoretical existence and sustainability of atmospheric habitable zones. 

To understand how the atmosphere of a Venus-like exoplanet would be observed, we will use an instrument simulator for the Mid-infrared ELT Imager and Spectrograph (METIS), one of the first instruments planned for the Extremely Large Telescope (ELT) at the European Southern Observatory. 

The UK Astronomy Technology Centre in Edinburgh is leading the design and build of the METIS LM-band spectrometer (LMS), which covers the wavelength range 2.7-5.5 microns. The LMS will combine the ELT’s unprecedented spatial resolution with very high spectral resolution and high contrast coronagraphic imaging, to open up a new parameter space ideal for the investigation of the atmospheric properties of exoplanets.  The coronagraph will provide contrasts of ~100,000 at angular separations six times smaller than JWST, while the high dispersion will enhance molecular species detection using the systematic spectral shift due to the planet’s orbital velocity. 

Requirements

The successful candidate will have a degree in the physical sciences and most likely physics, chemistry, or applied mathematics. This is a computational and data analysis project: no prior computing experience is necessary, but some knowledge of coding would be useful (e.g., Python, FORTRAN).

References

Gliese 12 b: 

https://academic.oup.com/mnras/article/531/1/1276/7679807

https://iopscience.iop.org/article/10.3847/2041-8213/ad3642

Venus photochemistry and clouds: 

https://www.sciencedirect.com/science/article/pii/S0019103523000246?via%3Dihub

METIS: 

https://arxiv.org/pdf/2103.11208  

The Exotic Worlds of exo-Titans

Dr Sarah Rugheimer

The search for habitable worlds beyond our solar system is one of the most exciting frontiers in modern astrophysics. Rocky exoplanets, especially those located in the habitable zones of their host stars, are prime candidates for exploring the conditions required for life. But we also want to not limit ourselves unduly to Earth-like environments. This PhD project aims to advance understanding of rocky exoplanets by modelling a type of atmosphere very different than Earth based on Saturn’s moon Titan. Titan in our Solar System is a target of interest to search for weird, non-Earth-like life and offers an environment due to its thick nitrogen-rich atmosphere, hydrocarbon chemistry, and methane-based hydrological cycle. Titan-like planets are thought to be one of the most common types of planets with stable atmospheres orbiting M dwarf host stars in the Universe (Lunine, 2009) and they are understudied compared to Earth analogues.

This research will develop 1D photochemical models to explore how such planets behave in diverse stellar environments, focusing on how ultraviolet radiation and stellar activity from FGKM stars influence their atmospheres. With exo-Titans potentially existing at a wide range of distances from their host stars, this project will determine how characterizable these exotic worlds are with current and future telescopes such as the James Webb Space Telescope (JWST), the Habitable Worlds Observatory (HWO), and the Large Interferometer for Exoplanets (LIFE). The findings will play a crucial role in assessing the viability of missions to discover and characterize Titan-like worlds, link to alternative life chemical experiments in the lab, and provide insights in characterizing exotic, non-Earth-like atmospheres that may also be habitable for weird life.

Successful applicants should have a strong background in coding.  

Under the Astrobiology projects, see also:

• Investigating the desiccation limits to life on Earth and elsewhere - Prof Charles Cockell

Under the Astronomical Instrumentation projects, see also:

• Performance testing the ELT/METIS/LMS spectrometer - Dr Alistair Glasse (UK ATC), Prof Beth Biller, and Prof Ken Rice