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ExoLunch - winter-2024

What can direct observations tell us about atmospheric escape?

Feb. 2, 2024
noon - 1 p.m.
3814 Geology

Presented By:

  • Ethan Schreyer - Imperial College London
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Atmospheric escape plays a significant role in the evolution of close-in small exoplanets. Due to the proximity of these planets to their host star, their upper atmosphere is extremely hot and escapes in the form of a hydrodynamic wind. This process can strip these planets of their primordial hydrogen/helium envelopes and has been used to explain the lack of short period Neptune sized planets (e.g. hot Neptune desert) and the bimodal radius distribution of small planets (e.g. radius valley). Despite much theoretical progress, there is still uncertainty in the specifics of the escape process. For example, whether mass loss is driven by high energy or bolometric irradiation or the role of planetary magnetic fields in controlling escape. Observations of atmospheric escape, via the transit method, provide an opportunity to directly test different escape models. In this talk, I will outline both what we can learn from these observations, and the challenges involved in translating these observations into constraints on the properties of the outflow. I will focus on my work modelling Lyman-α transits and helium 1083 nm transits, the latter in which we present a novel method to measure the magnetic fields of exoplanets undergoing atmospheric escape.