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Black Hole

Lensing of space time around a black hole. At Oxford we study black holes observationally and theoretically on all size and time scales - it is some of our core work.

Credit: ALAIN RIAZUELO, IAP/UPMC/CNRS. CLICK HERE TO VIEW MORE IMAGES.

Dr Jake Taylor (he/him)

Glasstone Fellow

Research theme

  • Astronomy and astrophysics
  • Exoplanets and planetary physics

Sub department

  • Astrophysics

Research groups

  • Exoplanet atmospheres
  • Exoplanets and Stellar Physics
jake.taylor@physics.ox.ac.uk
Denys Wilkinson Building, room 463
Person website
  • About
  • Prizes, awards and recognition
  • Publications

JWST NIRISS transmission spectroscopy of the super-Earth GJ 357b, a favourable target for atmospheric retention

Monthly Notices of the Royal Astronomical Society Oxford University Press 540:4 (2025) 3677-3692

Authors:

Jake Taylor, Michael Radica, Richard D Chatterjee, Mark Hammond, Tobias Meier, Suzanne Aigrain, Ryan J MacDonald, Loic Albert, Björn Benneke, Louis-Philippe Coulombe, Nicolas B Cowan, Lisa Dang, René Doyon, Laura Flagg, Doug Johnstone, Lisa Kaltenegger, David Lafrenière, Stefan Pelletier, Caroline Piaulet-Ghorayeb, Jason F Rowe, Pierre-Alexis Roy

Abstract:

We present a JWST Near Infrared Imager and Slitless Spectrograph/Single Object Slitless Spectroscopy transmission spectrum of the super-Earth GJ 357 b: the first atmospheric observation of this exoplanet. Despite missing the first 40 per cent of the transit due to using an out-of-date ephemeris, we still recover a transmission spectrum that does not display any clear signs of atmospheric features. We perform a search for Gaussian-shaped absorption features within the data but find that this analysis yields comparable fits to the observations as a flat line. We compare the transmission spectrum to a grid of atmosphere models and reject, to 3 confidence, atmospheres with metallicities solar (4 g mol−1) with clouds at pressures down to 0.01 bar. We analyse how the retention of a secondary atmosphere on GJ 357 b may be possible due to its higher escape velocity compared to an Earth-sized planet and the exceptional inactivity of its host star relative to other M2.5V stars. The star’s XUV luminosity decays below the threshold for rapid atmospheric escape early enough that the volcanic revival of an atmosphere of several bars of CO is plausible, though subject to considerable uncertainty. Finally, we model the feasibility of detecting an atmosphere on GJ 357 b with MIRI/LRS, MIRI photometry, and NIRSpec/G395H. We find that, with two eclipses, it would be possible to detect features indicative of an atmosphere or surface. Further to this, with three to four transits, it would be possible to detect a 1 bar nitrogen-rich atmosphere with 1000 ppm of CO.
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SiO and a super-stellar C/O ratio in the atmosphere of the giant exoplanet WASP-121 b

Nature Astronomy Nature Research 9:6 (2025) 845-861

Authors:

Thomas M Evans-Soma, David K Sing, Joanna K Barstow, Anjali AA Piette, Jake Taylor, Joshua D Lothringer, Henrique Reggiani, Jayesh M Goyal, Eva-Maria Ahrer, Nathan J Mayne, Zafar Rustamkulov, Tiffany Kataria, Duncan A Christie, Cyril Gapp, Jiayin Dong, Daniel Foreman-Mackey, Soichiro Hattori, Mark S Marley

Abstract:

Refractory elements such as iron, magnesium and silicon can be detected in the atmospheres of ultrahot giant planets. This provides an opportunity to quantify the amount of refractory material accreted during formation, along with volatile gases and ices. However, simultaneous detections of refractories and volatiles have proved challenging, as the most prominent spectral features of associated atoms and molecules span a broad wavelength range. Here, using a single JWST observation of the ultrahot giant planet WASP-121 b, we report detections of H2O (5.5–13.5σ), CO (10.8–12.8σ) and SiO (5.7–6.2σ) in the planet’s dayside atmosphere and CH4 (3.1–5.1σ) in the nightside atmosphere. We measure super-stellar values for the atmospheric C/H, O/H, Si/H and C/O ratios, which point to the joint importance of pebbles and planetesimals in giant planet formation. The CH4-rich nightside composition is also indicative of dynamical processes, such as strong vertical mixing, having a profound influence on the chemistry of ultrahot giant planets.
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JWST NIRISS Transmission Spectroscopy of the Super-Earth GJ 357b, a Favourable Target for Atmospheric Retention

(2025)

Authors:

Jake Taylor, Michael Radica, Richard D Chatterjee, Mark Hammond, Tobias Meier, Suzanne Aigrain, Ryan J MacDonald, Loic Albert, Björn Benneke, Louis-Philippe Coulombe, Nicolas B Cowan, Lisa Dang, René Doyon, Laura Flagg, Doug Johnstone, Lisa Kaltenegger, David Lafrenière, Stefan Pelletier, Caroline Piaulet-Ghorayeb, Jason F Rowe, Pierre-Alexis Roy
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Details from ArXiV

A Moderate Albedo from Reflecting Aerosols on the Dayside of WASP-80 b Revealed by JWST/NIRISS Eclipse Spectroscopy

Astronomical Journal American Astronomical Society 169:5 (2025) 277

Authors:

Kim Morel, Louis-Philippe Coulombe, Jason F Rowe, David Lafrenière, Loïc Albert, Étienne Artigau, Nicolas B Cowan, Lisa Dang, Michael Radica, Jake Taylor, Caroline Piaulet-Ghorayeb, Pierre-Alexis Roy, Björn Benneke, Antoine Darveau-Bernier, Stefan Pelletier, René Doyon, Doug Johnstone, Adam B Langeveld, Romain Allart, Laura Flagg, Jake D Turner

Abstract:

Secondary eclipse observations of exoplanets at near-infrared wavelengths enable the detection of thermal emission and reflected stellar light, providing insights into the thermal structure and aerosol composition of their atmospheres. These properties are intertwined as aerosols influence the energy budget of the planet. WASP-80 b is a warm gas giant with an equilibrium temperature of 825 K orbiting a bright late-K/early-M dwarf, and for which the presence of aerosols in its atmosphere has been suggested from previous Hubble Space Telescope and Spitzer observations. We present an eclipse spectrum of WASP-80 b obtained with JWST NIRISS/SOSS, spanning 0.68–2.83 μm, which includes the first eclipse measurements below 1.1 μm for this exoplanet, extending our ability to probe light reflected by its atmosphere. When a reflected light geometric albedo is included in the atmospheric retrieval, our eclipse spectrum is best explained by a reflected light contribution of ∼30 ppm at short wavelengths, although further observations are needed to statistically confirm this preference. We measure a dayside brightness temperature of TB=811−70+69 K and constrain the reflected light geometric albedo across the SOSS wavelength range to Ag=0.204−0.056+0.051 , allowing us to estimate a 1σ range for the Bond albedo of 0.148 ≲ AB ≲ 0.383. By comparing our spectrum with aerosol models, we find that manganese sulfide and silicate clouds are disfavored, while cloud species with weak-to-moderate near-infrared reflectance, along with soots or low formation-rate tholin hazes, are consistent with our eclipse spectrum.
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Are there Spectral Features in the MIRI/LRS Transmission Spectrum of K2-18b?

ArXiv 2504.15916 (2025)
Details from ArXiV

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