The Pale Green Dot: A Method to Characterize Proxima Centauri b using Exo-Aurorae

Understand

We examine the feasibility of detecting auroral emission from the potentially habitable exoplanet Proxima Centauri b.

• Detection of aurorae would yield an independent confirmation of the planet's existence, constrain the presence and composition of its atmosphere, and determine the planet's eccentricity and inclination, thereby breaking the mass-inclination degeneracy.
• If Proxima Centauri b is a terrestrial world with an Earth-like atmosphere and magnetic field, we estimate the power at the 5577\AA\ OI auroral line is on the order of 0.1 TW under steady-state stellar wind, or ${\sim} 100 {\times}$ stronger than that on Earth.
• This corresponds to a planet-star contrast ratio of $10^{-6}-10^{-7}$ in a narrow band about the 5577\AA\ line, although higher contrast ($10^{-4}-10^{-5}$) may be possible during periods of strong magnetospheric disturbance (auroral power $1-10$ TW).