Resonances and masses in TRAPPIST-1

Séminaire IPAG de Eric Agol (University of Washington & IAP), jeudi 16 novembre 2017 à 11h00, salle Manuel Forestini IPAG

The TRAPPIST-1 system took the astronomical community by surprise when it revealed seven transiting planets during a 20-day observation with the Spitzer Space Telescope (Gillon et al. 2017). This system provides an excellent opportunity to measure the masses, radii (hence densities), and atmospheres of Earth-sized and Earth-temperature planets in the Solar neighborhood with existing and upcoming ground and space-based facilities.

I will describe our recent progress in studying this system : 1). We predicted the period of the seventh planet — which just showed one transit in the Spitzer data — based on a series of Laplace resonances. We found this planet in a long K2 observation of the TRAPPIST-1 system, right at the predicted period. 2). We are continuing to monitor the transit times with the Spitzer Space telescope, and will examine how transit timing can lead to bulk densities of these planets. Transit timing is plagued by degeneracies, which we will describe, as well as how to overcome these with a measurement of "chopping." 3). We show with Monte Carlo that the planets are extraordinarily coplanar, within 0.3 degrees at 90% confidence. 4). In addition to transit transmission spectroscopy and secondary eclipse spectroscopy, planet-planet occultations may be detectable with JWST, and in the future the Origins Space Telescope, providing another means to break the transit timing degeneracies.