PICS Seminar: Brian Jackson (Boise State)

Brian Jackson, Boise State
Tuesday, September 19, 2017 - 12:30pm to 1:30pm

"Tidal Decay and Roche-Lobe Over ow of Short-Period Gaseous Exoplanets "

Discoveries of 100+ Earth-sized planet candidates with short orbital periods, some only a few hours, have challenged theoretical expectations. The proximity of hot Jupiters to Roche-Lobe over ow (RLO) has suggested some small short-period planets are actually the fossil cores of disrupted gaseous planets, and recent work provides some support: Stable RLO (atmospheres lost via a steady out ow and a thin accretion disk) can drive orbital expansion that stops and reverses at a maximum period that depends on the core mass, and some small short-period planets have periods consistent with this picture. However, the periods of the very closest-in planets are too short. Instead, unstable RLO (atmospheres quickly shed on dynamical timescales) may explain the small short-period planets. Indeed as disrupting hot Jupiters transition to hot sub-Neptunes, the accompanying radius evolution, as well as non-conservative angular momentum evolution, may drive the planets from stable to unstable RLO. On the other hand, simple scaling arguments suggest that the very short viscous timescale for the accretion disk may accommodate the increase in over ow rate that results from the radius evolution, allowing the RLO to remain stable after all. In this presentation, we will discuss recent work on planetary RLO and explore outstanding questions.

About the Series

The MIT Planetary Lunch Colloquium Series [PlCS] is a weekly seminar series organized within the EAPS department. Colloquia topics span the range of research interests of the department's planetary sciences research program. The seminars usually take place on Tuesdays from 12-1:30 pm in 54-517 unless otherwise noted (term-time only). Speakers include members of the MIT community and visitors. Talks are intended to appeal to graduate students, postdocs, research scientists, and faculty with a background in planetary science. A light lunch is provided.