Institute for Advanced Study Informal Astrophysics Seminar

Atmospheric escape or mass loss is an important process in the evolution of planetary atmospheres in the Solar System, as well as in extrasolar planets. However, there are many aspects of atmospheric escape in exoplanets that remain poorly understood, in part due to a small number of direct observations. Observational evidence of atmospheric escape has been obtained only for a few exoplanets to date, mostly via transit observations in the hydrogen Lyman-alpha line, which is inaccessible for ground-based observations and is heavily affected by interstellar absorption and geocoronal emission. The absorption line of helium at 10830 angstrom can overcome some of the main difficulties associated with the UV diagnostics. In this talk, I will present a model of escaping planetary atmospheres used to predict in-transit absorption at 10830 angstrom. Our results indicate that significant absorption at this wavelength can be expected in some exoplanets, which has recently been confirmed by observations with the Hubble Space Telescope and ground-based instruments. The helium 10830 angstrom line is accessible for ground-based observations using high-resolution spectrographs, which could enable more detailed studies of extended atmospheres for a much larger number of exoplanets than realistically possible with UV spectroscopy. By opening this new wavelength window into escaping atmospheres, we can improve our understanding of the physical processes that drive atmospheric mass loss and, consequently, affect planetary evolution and demographics of planetary systems.