Malena Rice

Orbital architectures


The geometry of a planetary system — characterized by the orientations and shapes of its constituent orbits, as well as the orientations of its spin vectors — offers a rich set of insights into how that system formed and evolved. Much of my research is driven by studies of planetary system geometries.

One measurable planetary system property that I have examined extensively in my research is the stellar obliquity, or the angle between a star's spin axis and the net orbital angular momentum vector of its surrounding planetary system. While the solar system planets each lie within a few degrees of alignment with the Sun's spin axis, exoplanets have been discovered on retrograde and polar orbits.

I founded and co-lead the Stellar Obliquities in Long-period Exoplanet Systems (SOLES) survey, through which my team measures the obliquities of systems hosting wide-separation planets using the Rossiter-McLaughlin effect. Planets with a relatively large orbital separation from their host star have long tidal realignment timescales and can be used to better understand the underlying, primordial stellar obliquity distribution, with fewer degeneracies than closer-in planets. New measurements from the SOLES survey can also help to disentangle the effect of tidal interactions on the distribution of observed hot Jupiter spin-orbit angles. I have worked to characterize hot and warm Jupiter formation mechanisms through population studies of exoplanet spin-orbit angles.

Recently, I demonstrated that the stellar obliquity distribution provides tantalizing hints consistent with high-eccentricity migration as the key hot Jupiter formation mechanism. Read my associated research highlight here.

In my research highlight here, I demonstrate an observed tendency toward alignment in single-star warm Jupiter systems, and I describe the implications of this finding for hot and warm Jupiter formation.

The eighth result from the SOLES survey demonstrates that near-resonant systems are generally consistent with a quiescent formation pathway, with some room for low-level protoplanetary disk misalignments or post-disk-dispersal spin-orbit excitation. Read more in the research highlight here.

Select associated publications