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Subhajit Sarkar

Dr Subhajit Sarkar

Astronomy Group
Astronomy Instrumentation Group
Cardiff Hub for Astrophysics Research and Technology

School of Physics and Astronomy

+44 29225 14790
Queen's Buildings - North Building, Room N/2.20, 5 The Parade, Newport Road, Cardiff, CF24 3AA
Available for postgraduate supervision


I'm a university lecturer and astrophysicist working in the field of extra-solar planets. I am involved in the development of new missions and observatories to characterise the atmospheres of exoplanets, in particular the ESA Ariel mission, as well as Twinkle and the NASA EXCITE mission.  I also am involved in cycle 1 and cycle 2 JWST exoplanet observations in collaboration with IoA Cambridge. I am interested in understanding atmospheric and planetary processes in temperate regime sub-Neptunes and gas giants, and how these relate to fundamental questions of planet formation and the diversity of the exoplanet population.  I am also interested in astrobiology, particularly the potential for biospheres in temperate sub-Neptunes and gas giants, how we may be able to determine the frequency of life-bearing worlds (the fL factor in the Drake Equation) and how exoplanetary observations might be able to constrain theories of the origin of life.






















Research vision

1. Searching for life in the Universe

      • Atmospheric characterisation/analysis of potentially habitable worlds to identify biosignatures.

        • Exploration of Sub-Neptunes and "Hycean" worlds  with JWST (in collaboration with N. Madhusudhan).
          • I am Co-I on JWST GO 2722:
            'Chemical Disequilibrium in a Temperate sub-Neptune'. Approx. 20 hours. We used NIRISS, NIRSpec and MIRI to obtain the transmission spectrum of the sub-Neptune K2-18 b from 0.6 to 12 microns. 
          • I am Co-I on JWST GO program 3557:
            'A JWST Search for Missing Methane'.  Approx. 70 hours.  We are using NIRISS, NIRSpec and MIRI to obtain transmission spectra for 4 sub-Neptune/Neptune-sized planets: potential Hycean candidates.   
      • Modelling approaches 

        • Statistical modelling
          • See my paper in MNRAS on the "DRAKE mission" concept, that predicts stastistical uncertainties on fL, the frequency of life factor in the Drake Equation.
          • I am interested in developing atmospheric models to further our quanitification of biosignature signals.

2.  Characterising and explaining the diversity of exoplanets and planetary systems 

      • Atmospheric characterisation observations of exoplanets

        • JWST observations
          • See JWST Sub-Neptune observational programme above.
          • I work on JWST pipeline optimisation to extract atmospheric spectra.  I am developing JexoPipe, and have thus far applied this to WASP-39 b (see my recent paper in MNRAS) and K2-18 b.  JexoSim, a time-domain observational simulator was also developed to provide mock input data for pipelines, which we hope to update soon.
        • Twinkle Cool Gas Giant Survey (2025-)
          • I am leading the cool giant W/G and the design for this survey for the upcoming Twinkle mission. The aim is to sample a large number of cool temperate gaseous planets: a "missing link" between the hot Jupiters and the cold giants of our own Solar System.  We will analyse for composition, atmospheric processes and sample level trends to chart this poorly explored parameter space.  See our preliminary simulation/retrieival study in MNRAS (Booth et al 2024).
        • HST observations
          • We are analysing HST transit spectroscopy data as well.  With my student Luke Booth, we have worked on characterising the atmosphere of LTT-9779 b, a planet in the hot Neptune desert, and also on changes in the atmosphere of the hot Jupiter HD 209458 b over different epochs.
        • Ariel
          • I have been extenstively involved in performance simulations for the Ariel mission (launch 2029). I also developed the original Ariel pipeline, ADaRP, and several versions of the Ariel simulator, ExoSim.  I have served as Ariel simulations W/G lead and on several ground segment and science working groups.  I convene the Ariel W/G on complimentary science.  I am co-I on the UKSA Cardiff Ariel grant.  

        • EXCITE
          • I carried our performance simulations and am a NASA collaborator on EXCITE, a stratospheric balloon observatory to observe exoplanet phase curve spectra.  


Software developed

  • ExoSim, SpotSim, ExoSim_N, JexoSim (JWST simulator), TwinkleSim, ADaRP, JexoPipe


Current undergraduate teaching

  • PX4245 / PXT145 Exoplanets and the Search for Life: Module Organiser
  • PX2140 Stars and Planets: Deputy Module Organiser

Previous undergraduate teaching

  • PX1127 Planet Earth: Module Organiser
  • PX2140 Stars and Planets: guest lecturer
  • PX1127 Planet Earth: Deputy Module Organiser
  • PX2134 Structured Programming: Lab supervisor
  • PX1125 Mathematical Practice for Physical Sciences: Marker
  • PX1222 Mathematical Methods for Physicists 2: Marker


  • I supervise PhD, MPhys, MSc and BSc research projects (see supervision page)



  • PhD, Astrophysics, Cardiff University
  • MSc (Distinction), Space Science, University College London
  • Diploma in Physics (Distinction), Open University
  • MA, Natural Sciences, Cambridge University
  • MB, BChir, Medicine, Cambridge University
  • Grad. Cert. Applied Sciences, Space Studies, University of South Australia
  • Space Studies Program, International Space University

Professional memberships

  • Fellow of the Royal Astronomical Society
  • Fellow of the Higher Education Academy

Academic positions

  • 2022- Present: Lecturer in Exoplanet Characterisation, School of Physics and Astronomy, Cardiff University
  • 2017-2021: Post-doctoral Research Associate, Cardiff University
  • 2013-2017: Post-graduate Research Student, Cardiff University
  • 2003-2005: Visiting Researcher, Space Medicine & Health Care Systems Office, NASA Johnson Space Center, Houston.
  • 2003-2005: Honorary Lecturer in Space Life Sciences, Dept. of Space & Climate Physics, University College London

Outreach and Media

  • BBC Radio Wales Science Cafe interview about the ARIEL space mission (April 2018).
  • Pythagorean Astronomy podcast interview about TESS, ARIEL and other exoplanet missions (April 2018).
  • Exoplanet talks for Cardiff AS Level Summer Programmes 2018/19.
  • Stargazing talk and telescope observing with Scouts (Spring 2019).
  • Online astronomy talk with Scouts (Winter 2020).
  • 'All About Space' magazine interview about Ariel mission ('Rise of the Exoplanet Hunter') (Jan 2021).
  • Twinkle mission YouTube video ('The Founding Members') (Aug 2021).
  • Pythagorean Astronomy podcast interview about JWST observing programme (Dec 2021).
  • Cardiff School of Physics & Astronomy YouTube video about JWST (Dec 2021).
  • BBC News Wales interview about exoplanets and JWST (July 2022).
  • Nature News and Views article on JWST (Feb 2023).
  • NASA/ESA Press release on JWST K2-18 b observation (Sep 2023)
  • BBC News interview ('Alien life in the Universe') (Sep 2023)
  • K2-18 b international interviews including: Le Parisien, Hindustan Times, News9Live (India), Kosmo magazine (Italy) (Sep/Oct 2023)
  • IoP Festival of Physics, keynote speaker ('Exoplanets and the Search for Life') (Nov 2023)
  • Astronomy on Tap (Cardiff) speaker (Nov 2023)

Committees and reviewing

  • I am the post-graduate admissions tutor for the Astronomy Group. 
  • I currently serve on the following school committees: a) Equality, diversity and inclusion (EDI), b) Environment and sustainability.
  • I am on the CHART-GEI Schools Engagement Project management team and the Astronomy Instrumentation Group management team.
  • I have previously served on the Ethics committee and MSc approval panel.
  • JWST TAC exoplanet panel member for cycle 3
  • Grant reviewer for French National Research Agency.
  • I have refereed publications for journals including PASP, RASTI and Nature.


Current supervision

  • I am primary PhD supervisor for Luke Booth who is researching exoplanet atmospheres.
  • I am currently on the supervisory team as mentor for two PhD students.
  • I currently supervise the undergraduate projects "Missions to the planets" and "Exoplanet transmission spectroscopy"

Current supervision

Luke Booth

Luke Booth

PhD Student/Research Assistant

Past projects

  • Previous undergraduate and MSc projects include:  "Habitable exomoons", "Transmission spectroscopy of water", "Designing a telescope to observe Earth-like planet atmosphere", "Simulations for the Twinkle space mission", "Impact of star spots on exoplanet transmission spectroscopy"