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  Characterising the atmospheres of exoplanets with ground-based and JWST observations

   Department of Physics

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  Dr Siddharth Gandhi  Applications accepted all year round  Funded PhD Project (Students Worldwide)

About the Project

We invite applications from outstanding and highly motivated students for the Warwick Prize Scholarships in Astrophysics. The successful applicant will work with Dr Siddharth Gandhi within the Astronomy and Astrophysics group in the Department of Physics at the University of Warwick.

In this project you will use data from ground-based telescopes such as the VLT and space-based observations from JWST to characterise the atmospheres of transiting and directly imaged exoplanets. This will constrain the chemical composition, including isotope ratios, and the thermal profile of the atmosphere, allowing us to compare and contrast close-in planets to those further away from their star, and provide context to the Solar System.

We can probe the chemical composition of exoplanetary atmospheres from both from ground and space facilities. From the ground, telescopes such as VLT and the upcoming ELT enable very high spectral resolution observations, and allow us to very precisely determine chemical signatures as well as orbital motion of the planet. On the other hand, space-based observations through the recently launched JWST enable characterisation of exoplanetary atmospheres unobstructed by our own atmosphere. Both are capable of very high precision constraints on the atmosphere for a range of exoplanets and can be used in tandem for robust chemical characterisation of the atmosphere.

The most common method by which we characterise the atmospheres of exoplanets is through the transit method. As the planet passes in front of its host star as observed by us, part of the stellar light shines through the atmosphere. At certain wavelengths, the atmosphere will appear opaque as the chemical species present in the atmosphere block the light. We can use this to determine the chemical composition, temperature profile and any clouds/hazes present in the atmosphere as well as using these to trace the formation history of the planet.

Recently, there have been a growing number of exoplanets characterised through direct imaging. As the name suggests, this technique allows us to separate the planet light from the star light on the sky and observe the emission coming from the planet directly. Typically, we need high mass and/or newly formed exoplanets that are distant from their host to be able to resolve them from the bright starlight by our instruments, but they provide an excellent contrast to the transiting exoplanets which are much closer-in to their star.

One of the major developments of the last couple of years has been isotope chemistry of exoplanetary atmospheres. Constraining 13C/12C or 18O/16O ratios in the atmosphere can give us a handle for where in a protoplanetary disk the planet may have formed. As we go further out in a planet forming disk, these ratios vary due to processes such as photodissociation, isotope exchange reactions and differing ice binding rates between isotopes. Therefore, getting the isotopic ratios of the atmosphere provides a key insight into planetary formation.

The aim of this project will be to constrain the chemical composition of a range of exoplanets and determine the similarities and differences between planets close-in and further away from their star. We will also use the chemical composition, including the isotope ratios, to trace the formation history to determine how these planets may have formed and how they migrated to their current orbits and compare their composition to the Solar System.

Warwick is an internationally recognised centre of research excellence. Our group takes leading roles in many major ground and space-based projects, including the Gravitational-wave Optical Transient Observer (GOTO), Next Generation Transit Survey (NGTS), PLAnetary Transits and Oscillations of stars (PLATO) telescope, Sloan Digital Sky Survey (SDSS), WHT Enhanced Area Velocity Explorer (WEAVE) spectrograph, 4-metre Multi-Object Spectrograph Telescope (4MOST), Dark Energy Spectroscopic Instrument (DESI), and CHaracterising ExOPlanet Satellite (CHEOPS).

The Astronomy & Astrophysics group is part of the Physics Department at Warwick; both the department and the university hold Athena SWAN Silver awards, a national initiative to promote gender equality for all staff and students. The Physics Department is also a Juno Champion, which is an award from the Institute of Physics to recognise our efforts to address the under-representation of women in university physics and to encourage better practice for all. The Astronomy & Astrophysics group also hosts monthly equitea forums to break down barriers faced by all under-represented groups in science.

More details on PhD positions with the Astronomy and Astrophysics group at Warwick are available here.

Start Date: October 2024

Funding Duration: 3.5-4.0 years

Applications due by: 9 January 2024


You must have or expect a First or Upper second class MSci, MPhys or equivalent degree in Physics or a closely related discipline. Holders of BSc honours degrees are eligible but successful BSc applicants typically have substantial additional research experience. International equivalents are detailed here.

For students whose first language is not English, we normally require a score of 6.5 in IELTS or equivalent. If your previous degree was taught in an English-speaking country this requirement may be waived. See this page.

The award is available to home and international applicants.

How To Apply

You must apply through the University’s online application system and follow the instructions. Use course code P-F3P0, and see our Frequently Asked Questions. Make sure to state an interest in the Astronomy and Astrophysics group. Please state ‘Warwick Prize Scholarships’ as the funding option. We encourage applicants to express interest in more than one available PhD project.

 Funding Notes

The project will provide a full UK-standard annual tax-free stipend of £19,237, rising with inflation, plus allocations for travel and computing.

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 About the Project