Can Ground-based Telescopes Detect The Oxygen 1.27 Micron Absorption Feature as a Biomarker in Exoplanets ?

TL;DR

This study evaluates the potential for ground-based 30-meter class telescopes to detect the oxygen 1.27 micron absorption feature in exoplanets, a key biomarker, considering atmospheric interference and instrument capabilities.

Contribution

It demonstrates the feasibility of detecting the oxygen absorption band in Earth-like exoplanets around late-type stars using future ground-based telescopes with advanced coronagraphs and adaptive optics.

Findings

Night airglow at 1.27 micron declines significantly by midnight.

Photon noise from night airglow dominates detection limits.

Approximately 50 nearby late-type stars could host detectable Earth twins.

Abstract

The oxygen absorption line imprinted in the scattered light from the Earth-like planets has been considered the most promising metabolic biomarker of the exo-life. We examine the feasibility of the detection of the 1.27 micron oxygen band from habitable exoplanets, in particular, around late- type stars observed with a future instrument on a 30 m class ground-based telescope. We analyzed the night airglow around 1.27 micron with IRCS/echelle spectrometer on Subaru and found that the strong telluric emission from atmospheric oxygen molecules declines by an order of magnitude by midnight. By compiling nearby star catalogs combined with the sky background model, we estimate the detectability of the oxygen absorption band from an Earth twin, if it exists, around nearby stars. We find that the most dominant source of photon noise for the oxygen 1.27 micron band detection comes from the night airglow if the contribution of the stellar PSF halo is suppressed enough to detect the planet. We conclude that the future detectors for which the detection contrast is limited by photon noise can detect the oxygen 1.27 micron absorption band of the Earth twins for ~50 candidates of the late type star. This paper demonstrates the importance of deploying small inner working angle efficient coronagraph and extreme adaptive optics on extremely large telescopes, and clearly shows that doing so will enable study of potentially habitable planets.