Reflected light from giant planets in habitable zones: Tapping into the power of the Cross-Correlation Function

TL;DR

This paper explores using the Cross-Correlation Function with next-generation telescopes to detect reflected light from habitable zone exoplanets, aiming to improve atmospheric characterization despite extremely low flux ratios.

Contribution

It introduces a method combining the Cross-Correlation Function with advanced telescopes to detect reflected light from habitable zone exoplanets, extending previous successful detections.

Findings

Potential detection of reflected spectra for 5 habitable zone planets

Estimated observation times for successful detection

Demonstrated feasibility with next-generation facilities

Abstract

The direct detection of reflected light from exoplanets is an excellent probe for the characterization of their atmospheres. The greatest challenge for this task is the low planet-to-star flux ratio, which even in the most favourable case is of the order of $10^{-4}$ in the optical. This ratio decreases even more for planets in their host habitable zone, typically lower than $10^{-7}$. To reach the signal-to-noise level required for such detections, we propose to unleash the power of the Cross Correlation Function in combination with the collecting power of next generation observing facilities. The technique we propose has already yielded positive results by detecting the reflected spectral signature of 51 Pegasi b (see Martins et al. 2015). In this work, we attempted to infer the number of hours required for the detection of several planets in their host habitable zone using the aforementioned technique from theoretical EELT observations. Our results show that for 5 of the selected planets it should be possible to directly recover their reflected spectral signature.