Research

Given the dominant role we think Jupiter and Saturn played in the early history of our solar system, it is critical that we understand how extrasolar gas giants shape the lives of other worlds. My group uses radial velocity data to calculate the frequencies of gas giants in systems with different populations of inner planets, with a particular focus on super-Earths. Exploring how these frequencies vary as a function of properties like stellar metallicity/mass and gas giant eccentricity/separation/multiplicity allow us to constrain how gas giants interact with and impede the flow of planetary building blocks to the inner disk, how these systems dynamically evolved, and how these two together can inform the prospects for the habitability of these small worlds.

How to tilt an exoplanet

When we look at how planetary spin axes are tilted relative to their orbits in the solar system, we see a range of orientations - Uranus is on its side, Venus is spinning upside down, Saturn has a 27 degree tilt. These tilts, or "obliquities", tell us stories of formation and evolutionary histories. Measuring these obliquities for exoplanets is observationally challenging, requiring high-resolution spectroscopy, time-series photometry, and astrometry for the planet. We have measured the first handful of planetary obliquities outside the solar system, allowing us to test scenarios like giant impacts, secular spin-orbit resonances, and gravito-turbulence.

Image credit: Lawrence Sromovsky, University of Wisconsin-Madison/W.W. Keck Observatory/NASA

The two most fundamental building blocks of gas giants are hydrogen and metals. Depending on formation scenario, the metal-to-hydrogen ratio may vary widely.  We use precise mass and radius measurements for samples of non-inflated gas giants along with interior structure models to estimate bulk metal enrichment. With this we can explore how metal enrichment of gas giants can depend on things like disk masses, dynamical histories, accretion regimes, and formation efficiency.

Planetary atmospheres are three dimensional. Recently, 3D modelling work explored a critical question: How do magnetic fields shape a planet's atmospheric circulation? We leverage phase-resolved high-resolution spectra to hunt for signatures of magnetic drag in ultra-hot Jupiter atmospheres.

Image credit: NASA/JPL-Caltech

Clues to past formation histories are imprinted on planetary spectra. We use near-IR high-resolution spectra of young directly imaged planets to constrain atmospheric properties like metallicities, carbon-to-oxygen ratios, isotopologue ratios, and cloud properties. These can tell us about how, when, and where these planets form.

Image credit: NASA/JPL-Caltech/SwRI/MSSS/Gerald Eichstaedt/ Seán Doran