Exoplanet imaging speckle subtraction: current limitations and a path forward

Abstract

The direct detection and detailed characterization of exoplanets using extreme adaptive optics (ExAO) is a key science case of both current and future telescopes. However, both quasi-static and residual atmospheric wavefront errors currently limit the sensitivity of this endeavour, generating “speckles” in a coronagraphic image that initially obscure any faint exoplanet(s) from detection.

I first demonstrate the current limits of exoplanet imaging using datasets taken with the Gemini Planet Imager and Subaru Coronagraphic ExAO systems. Even when using advanced post-processing algorithms, speckle evolution over time and wavelength is shown to limit the final contrasts that can be reached with current state- of-the-art instruments. A new approach is thus needed to detect fainter exoplanets below these limits.

I then illustrate a path forward to reach contrasts near the fundamental photon noise limit: fast focal plane wavefront sensing of both quasi-static and atmospheric speckles. My new method, called the Fast Atmospheric Self-coherent camera Technique (FAST), deploys new hardware and software to overcome these limitations. Looking toward the future, the contrast improvements from fast focal plane wave- front sensing techniques such as FAST are expected to play an essential role in the ground-based detection and characterization of lower mass exoplanets.