Alastair Claringbold
I am a PhD student in the Astronomy and Astrophysics Group at the University of Warwick, supervised by Peter Wheatley. My research focus is on learning about the atmospheres of exoplanets, planets outside of our solar system. By observing exoplanets as they eclipse the stars they orbit with telescopes on the ground and in space, we can determine what gases and clouds make up the skies of these distant planets. We do this by splitting up the starlight into its constituent wavelengths with a spectrograph and looking for the characteristic features of molecules, atoms, clouds, and hazes in the resulting spectrum, a technique called transmission spectroscopy.
My research spans the complete process of learning about an atmosphere using transmission spectroscopy, including:
- Making predictions of features that could be detected in exoplanet atmospheres,
- Writing proposals for telescope time (including the JWST in space, and ESO telescopes in Chile),
- Observing the transiting planets,
- Reducing and analysing the data to obtain a spectrum,
- Figuring out what the spectrum tells us using atmospheric models and statistical methods (atmospheric retrieval),
- Contextualising these results with computer simulations of atmospheres (including radiative transfer and chemical kinetics).
Research Interests
My works focuses on using transmission spectroscopy at a range of wavelengths from visible blue light (~350 nm) to the thermal infrared emitted by the human body (~12 μm), to answer the following questions:
- What are temperate Jupiter atmospheres made of?
- How can we learn about the formation and migration of gas giant planets from the composition of their atmospheres?
- What determines the level of clouds or haze in gas giant planet atmospheres?
- Where can we detect prebiosignatures - chemicals produced by chemical processes like impacts, lightning, stellar activity, and volcanism, associated with the origin of life?
Temperate Jupiters
The gas giants of our solar system, Jupiter and Saturn, are much colder than Earth (less than -100˚C, ~150K). However, all of our studies of gas giant atmospheres thus far have been of hot Jupiters, which are much hotter (over 1000˚C, ~700K)! In between these two groups of planets are temperate Jupiters, which are gas giants like our own Jupiter, but with temperatures much closer to those found on Earth (250-500 K). These exoplanets are therefore an unknown quantity.
I am leading a JWST cycle 2 programme (PID: 4227) using JWST to observe the atmosphere of TOI-1899b, a gas giant planet with an atmospheric temperature of 370 K (about 100˚C). This programme, as well another JWST cycle 2 programme to observe another temperate gas giant Kepler-86b (PID: 3235), will grant the first ever look at the chemistry and clouds of temperate gas giants.
Gas giant formation and migration
A key question in exoplanetary science is using the current atmospheric composition of exoplanets to try and understand their formation and migration history. One way we can do this is by looking for systematic differences in chemical composition between planets with differing properties indicative of differences in their formation and migration history.
In the BOWIE-ALIGN programme (PID: 3838), led by Dr James Kirk and Dr Eva-Maria Ahrer, we are observing a sample of 6 hot Jupiters with JWST, 3 of which have aligned orbits, and 3 of which have misaligned orbits, and searching for a systematic difference in their chemistry. I am leading the data analysis for HAT-P-30b, one of the misaligned planets in the sample, as well as contributing to the retrieval analysis of all of the planets in the sample.
Clouds and hazes in gas giants
I am a member of the Low Resolution Ground-Based Exoplanet Atmosphere Survey using Transmission Spectroscopy (LRG-BEASTS, “large beasts”). In this survey we have obtained the optical transmission spectra of many hot Jupiters, which can allow us to understand trends in cloudiness and haziness, which is readily apparent in optical spectra, across the hot gas giant population. I am leading the analysis of HAT-P-44b, a hot Jupiter observed with the William Herschel Telescope (WHT) on La Palma, and have also observed LRG-BEASTS targets using the ESO New Technology Telescope (NTT) in La Silla, Chile.
Prebiosignatures
Molecules like hydrogen cyanide, HCN, and cyanoacetylene, HC3N, are implicated in the origin of life as they have been used by chemists to synthesise precursor molecules to RNA, proteins, and other biological molecules. Atmospheric processes including lightning, stellar activity, planetary impacts, and volcanism are also necessary processes for the origin of life in some scenarios. We can therefore link origin of life chemistry to astronomy by looking for prebiosignatures, features which indicate the presence of molecules or processes associated with the origin of life.
By searching for prebiosignatures, we can understand the ubiquity of both prebiotic molecules and prebiotic processes, even in planets incapable of hosting life. This lets us constrain the feasibility of different origin of life scenarios. My previous work undertaken during my integrated master's degree at the University of Cambridge, involved radiative transfer modelling of atmospheres containing prebiosignature molecules with JWST, and performing detection tests and full retrievals to estimate their detectability, under the supervision of Paul Rimmer and Sarah Rugheimer.
Teaching
I demonstrate the A2: Astronomical Spectroscopy for 2nd year undergraduate students at the University of Warwick, and I supervise Part II Astrophysical Fluid Dynamics for 3rd year undergraduate students at the University of Cambridge.
Publications
- Prebiosignature Molecules Can Be Detected in Temperate Exoplanet Atmospheres with JWST, A. B. Claringbold et al., 2023, AJ, 166, 39