Event time:
Thursday, February 24, 2022 - 2:30pm
Speaker:
Fei Dai
Speaker Institution:
Caltech
Talk Title:
Probing Planet Formation with the Most Extreme Cases
Event description:
With Luvoir/HabEx and GMT/TMT recommended by the decadal survey. The detection of biosignatures on exoplanets may be just a few decades ahead of us. However, there are still major gaps of knowledge in our understanding of planet formation, evolution, and habitability. The most extreme exoplanets are ideal for isolating and magnifying critical aspects of planet formation that are still missing in our current theories, that also gave rise to their observed peculiar properties.
At the hottest extreme of planet formation are the ultra-short-period planets (USP, orbital period ~1 day, <2 R_earth) which seemed impossible to have formed in-situ. Yet, they are the most observationally favorable rocky planets for mass measurement, phase curve, transmission, and mass loss studies. Our earlier investigation revealed a likely formation pathway and a prevalence of Earth-like rocky composition among these planets. Our upcoming JWST program will probe their surface mineralogy through phase curve variations. On a longer timescale, USPs will remain an important laboratory for understanding tidal deformation, volcanism, and transient atmospheres.
The “super-puffs” (planets with anomalously low density <0.1 g cm^-3) are young planets that are extremely susceptible to rapid atmospheric erosion with a timescale that is much shorter than the system’s age. I will introduce a scenario that involves ongoing atmospheric erosion and dust entrainment to explain the “super-puffs”. Further study of super-puffs and planetary mass loss in general will help us understand the fate of the primordial H/He atmosphere and secondary atmospheres.
Finally, we will describe a few novel methods that reveal planets on “oblique orbits” with respect to their host stars and a distant binary companion. I will discuss a population of planets on polar orbits that might have initially formed further out in the disk before they dynamically arrived at their current-day, close-in, misaligned orbits. The heat generated in the migration might have also triggered an episode of intense atmospheric erosion. The Nice and Grand Tack models have far-reaching implications for the architecture of our solar system. Exoplanets on oblique orbits will remain important signposts for studying similar large-scale dynamical upheavals.
