A JWST Transmission Spectrum of a White Dwarf Exoplanet

One day, the Sun will die. While the outer giant planets in our solar system will likely survive the death of the Sun, their long-term state is a matter of considerable uncertainty [1]. Recently, several intact giant exoplanets have been discovered orbiting white dwarfs [e.g., 2,3], which can provide a glimpse into the eventual fate of our solar system. I will present the first JWST observations of a giant planet orbiting a white dwarf: WD 1856b. WD 1856b orbits its host white dwarf at 0.02 au, causing considerable debate about how the planet survived the red giant phase and migrated inwards post main-sequence [e.g., 4,5]. Our NIRSpec PRISM transmission spectrum of WD 1856b accomplishes the first atmospheric detection of a white dwarf planet and offers dazzling insights into the evolutionary history of this extreme planetary system. Our results also provide the first insights into the atmospheric chemistry and aerosol properties of a post main-sequence exoplanet.

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[2] Vanderburg+2020, Nature 585, 363

[3] Blackman+2021 Nature 598. 272

[4] O’Connor+2021 MNRAS 501, 507

[5] Lagos+2021 MNRAS 501, 676