Early Release Science of the exoplanet WASP-39b with JWST NIRISS.
Adina D FeinsteinMichael RadicaLuis WelbanksCatriona Anne MurrayKazumasa OhnoLouis-Philippe CoulombeNéstor EspinozaJacob L BeanJohanna K TeskeBjörn BennekeMichael R LineZafar RustamkulovArianna SabaAngelos TsiarasJoanna K BarstowJonathan J FortneyPeter GaoHeather A KnutsonRyan J MacDonaldThomas Mikal-EvansBenjamin V RackhamJake TaylorVivien ParmentierNatalie M BatalhaZachory K Berta-ThompsonAarynn L CarterQuentin ChangeatLeonardo A Dos SantosNeale P GibsonJayesh M GoyalLaura KreidbergMercedes López-MoralesJoshua D LothringerYamila MiguelKaran MolaverdikhaniSarah E MoranGiuseppe MorelloSagnick MukherjeeDavid K SingKevin B StevensonHannah R WakefordEva-Maria AhrerMunazza K AlamLili AldersonNatalie H AllenNatasha E BatalhaTaylor J BellJasmina BlecicJonathan BrandeClaudio CaceresS L CasewellKaty L ChubbIan J M CrossfieldNicolas CrouzetPatricio E CubillosLeen DecinJean-Michel DésertJoseph HarringtonKevin HengThomas HenningNicolas IroEliza M-R KemptonSarah KendrewJames KirkJessica KrickPierre-Olivier LagageMonika LendlLuigi ManciniMegan MansfieldE M MayN J MayneNikolay K NikolovEnric PalleDominique J M Petit Dit de la RocheCaroline PiauletDiana PowellSeth RedfieldLaura K RogersMichael T RomanPierre-Alexis RoyMatthew C NixonEverett SchlawinXianyu TanP TremblinJake D TurnerOlivia VenotWilliam C WaalkesPeter J WheatleyXi ZhangPublished in: Nature (2023)
The Saturn-mass exoplanet WASP-39b has been the subject of extensive efforts to determine its atmospheric properties using transmission spectroscopy 1-4 . However, these efforts have been hampered by modelling degeneracies between composition and cloud properties that are caused by limited data quality 5-9 . Here we present the transmission spectrum of WASP-39b obtained using the Single-Object Slitless Spectroscopy (SOSS) mode of the Near Infrared Imager and Slitless Spectrograph (NIRISS) instrument on the JWST. This spectrum spans 0.6-2.8 μm in wavelength and shows several water-absorption bands, the potassium resonance doublet and signatures of clouds. The precision and broad wavelength coverage of NIRISS/SOSS allows us to break model degeneracies between cloud properties and the atmospheric composition of WASP-39b, favouring a heavy-element enhancement ('metallicity') of about 10-30 times the solar value, a sub-solar carbon-to-oxygen (C/O) ratio and a solar-to-super-solar potassium-to-oxygen (K/O) ratio. The observations are also best explained by wavelength-dependent, non-grey clouds with inhomogeneous coverageof the planet's terminator.