Imaging Small Planets Around the Very Nearest Stars with METIS on ELT

Abstract

Space-based transit surveys have revolutionized our understanding of the frequency of small rocky planets at small orbital radii around sunlike stars. The next generation of extremely large telescopes will have the angular resolution and sensitivity to directly image rocky planets around the very nearest stars (Wang et al.). Here we predict yields of the METIS instrument (Brandl et al. 2018), planned for the European Southern Observatory (ESO) Extremely Large Telescope (ELT). Using Kepler occurrence rates, a selection of nearby stars, and simulated contrast curves based on an advanced model of coronagraphic imaging with adaptive optics with METIS on the ELT, we estimate the expected yield from METIS using Monte Carlo simulations. We find the METIS expected yield of planets in the N2 (10.0–12.5 μm) band which outperforms the L (3.6–4.0 μm) and M (4.8–5.0 μm) bands. We also determine the chance of at least one rocky planet detection in the contrast limited regime and at least one Jovian planet in the background limited regime. We find the yield per star and optimal revisit times to increase yield. Finally, we present an optimal observing strategy in order to maximize the possible yield for limited telescope time.