Current Research

Spin State of Exoplanets Orbiting within the Habitable Zone of M Dwarfs: Effects of a Companion in Resonance

One longstanding problem for the potential habitability of planets around small, cool stars, is that one would expect a planet which is close enough to the star to reside within the habitable zone to be tidally locked into a synchronously rotating spin state. There have been different approaches to potentially solve this problem, either dynamically, or through GCM models which depict how energy might be sufficiently transported from the day to the night side on synchronously rotating planets. Dynamical studies have thus far typically considered only two objects: the central star and the planet itself. However, many planetary systems have been found to be multiple and in compact resonance-chains, and so I am taking a different approach to this problem by considering the effects that a companion in a mean-motion resonance might have on the spin state

A companion in a mean-motion resonance can induce oscillatory variations in the mean-motion of the primary planet. We find that this can excite the spin-states of otherwise synchronously rotating planets. This can then result in pushing the planet into a completely stable, circulating spin state, creating what are effectively stellar days on the planet. We find that these days would be on the order of years or decades, depending on system parameters. One notable and exciting system which was recently discovered is the TRAPPIST-1 system, which contains seven terrestrial planets in a long resonant chain, with many lying right in the proverbial "habitable zone" of the system. My advisor, Brad Hansen, and I recently published paper in MNRAS, in which we use TRAPPIST-1 as inspiriation for an analogue system to showcase our model.

Example of simulation results modeling the spin state of planet TRAPPIST-1d, considering the effects of its nearest outer companion, TRAPPIST-1e. \( \gamma \) corresponds to the substellar point on planet d. The top panels and bottom panels differ only in slight changes in initial conditions, showcasing that chaos at early times (before tidal damping has acted long enough) can make ultimate limit cycles unpredictable. The bottom panel shows, however, that these simulations can eventually yield stable, circulating spin-states. This effectively creates stellar days on the planet that would otherwise be synchronously rotating. We also note that the simulation depicted in the top panel, while not exhibiting a circulating spin-state, still exhibits stable non-zero amplitude librations well after tidal damping would have normally damped amplitude to zero without the driving effects of the outer companion.

Advisor - Brad Hansen.

Past Projects

Determining stellar membership in star forming regions

Goal of refining the MYStIX catalog, which catalogs probable stellar membership in 18 Galactic massive star-forming complexes.

Senior Project at Cal Poly Pomona.

Advisor - Matthew Povich

Modeling the gas and dust in the circumstellar disk around T-Cha

Summer 2013 REU project at the SETI Institute in Mountain View, CA.

Advisor - Uma Gorti.

The Morphology of Dunes on Titan

Summer 2012 project at JPL in Pasadena, CA. My participation was through the CAMPARE program. Work was presented in poster at AAS, Winter 2013.

Advisor - Charles C. Hays