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Wednesday, October 20, 2021
4:00 PM - 5:00 PM
Online and In-Person Event

Astronomy Colloquium

Systems of Short-Period Exoplanets: Regularities and Anomalies
Sarah Millholland, NASA Sagan Fellow, Department of Astrophysical Sciences, Princeton University,

Multiple-planet systems composed of close-in super-Earth/sub-Neptune-sized planets are ubiquitous, representing a dominant outcome of planet formation. This population exhibits predictable hallmarks of architectural regularity and uniformity, such as low eccentricities and inclinations, similar orbital spacings, and intra-system correlations in planetary masses and radii. On top of this first-order structure, however, these systems also exhibit surprising anomalies that require explanations. Examples include (1) ultra-short period planets that have been separated off from the rest of their systems; (2) planet pairs with orbital periods related by a ratio of small integers; and (3) planets that show signs of anomalous radius inflation. In this talk, I will propose that planet-planet and planet-star dynamical interactions can account for these specific anomalies and more. Specifically, I will focus on the role of tidal dissipation due to non-zero planetary axial tilts (obliquities). I will highlight strategies for testing tidal theories and measuring obliquities in the future.

To view this talk via YouTube, please visit:

For more information, please contact Jim Fuller by email at or visit