Hello, I’m Will Balmer.

As a member of the JWST Telescope Scientist Team (JWST-TST), I used guaranteed time observations planned by our high contrast imaging group at STScI to reveal the atmospheres of the iconic HR 8799 planets at never-before-seen wavelengths of light. The data is described in a first author paper I published in March 2025. The paper had a press release, found here. This result validates the findings of our ExoGRAVITY collaboration paper on the system, that the four gas giants in the HR 8799 system appear to be metal rich compared to their host star. This places fascinating constraints on the timing of their formation and their accretion history. In order to block the light from the bright host star and reveal these faint planets, we used a novel mode of the Near Infrared Camera (NIRCam) coronagraph, placing all the observations at the narrowest end of the underutilized wedge shaped mask.

One 8 meter telescope is fine, but why not use four 8 meter telescopes at the same time? I use the K-band (2-2.5 micron) beam combining instrument GRAVITY at the Very Large Telescope Interferometer (VLTI) to study exoplanets and brown dwarfs as a member of the ExoGRAVITY collaboration. Using optical interferometry, we make very precise measurements of the orbital motion of giant planets, and collect spectra containing information about the abundances of carbon and oxygen bearing molecules in their atmospheres. I used these techniques to study the orbit, composition, and formation of one of the lowest mass exoplanets directly imaged from the ground, AF Leporis b. In my first author paper on the system, I showed that the planet’s orbit is effectively circular, and the planet’s atmosphere is cloudy and strongly vertically mixed. I also evaluated some degeneracies in the Bayesian modeling of the atmosphere, showing why previous studies had overestimated the planet’s metallicity (hint: the fault is in our simplistic models of clouds and their impact on the planet’s spectrum). This ensemble of results shows that the current day properties of AF Lep b are consistent with predictions made by the core accretion formation model, and more generally, formation within a protoplanetary disk.