FEASIBILITY STUDIES FOR THE DETECTION OF O₂IN AN EARTH-LIKE EXOPLANET

Abstract

We present the results of simulations on the detectability of O 2 in the atmosphere of Earth twins around nearby low mass stars using high resolution transmission spectroscopy. We explore such detectability with each of the three upcoming Extremely Large Telescopes (ELTs), i.e. GMT, TMT and E-ELT, and high resolution spectrographs, assuming such instruments will be available in all ELTs. With these simulations we extend previous studies by taking into account atmospheric refraction in the transmission spectrum of the exo-Earth and observational white and red noise contributions. Our studies reveal that the number of transits necessary to detect the O 2 in the atmosphere of an Earth twin around M-dwarfs is by far higher than the number of transits estimated by Snellen et al. (2013). In addition, our simulations show that, when accounting for typical noise levels associated to observations in the optical and near-infrared, the O 2 A-band at 760 nm is more favorable to detect the exoplanetary signal than the O 2 band at 1268 nm for all the spectral types, except M9V. We conclude that, unless unpredicted instrumental limitations arise, the implementation of pre-slit optics such as image slicers appear to be key to significantly improve the yield of this particular science case. However, even in the most optimistic cases, we conclude that the detection of O 2 in the atmosphere of an Earth twin will be only feasible with the ELTs if the planet is orbiting a bright close-by (d ≤ 8 pc) M-dwarf with a spectral type later than M3.

PREDICTIONS OF THE ATMOSPHERIC COMPOSITION OF GJ 1132b

“…The planet's transmission and emission spectra are sensitive to the relative abundances of O 2 , H 2 O, and other species (Benneke & Seager 2012), and these spectra will be measurable with deep observations from the ground (Snellen et al 2013;Rodler & López-Morales 2014) or from space (Cowan et al 2015;Barstow et al 2016, and references therein). Complementary JWST observations of GJ 1132b's thermal phase curve could reveal its total atmospheric mass, and therefore determine whether the present-day atmosphere is thick or tenuous (Selsis et al 2011;Koll & Abbot 2015).…”

Atmospheric characterization of Proxima b by coupling the SPHERE high-contrast imager to the ESPRESSO spectrograph

“…We thus need to first examine when the planetary spectral lines are well separated from the telluric ones. As an example, Rodler & López-Morales (2014) derive the optimal relative RVs between the planetary and telluric O 2 A-bands (their Fig. 4), showing that relative RVs of ± (15-30) km s −1 are particularly suitable.…”

The Breakthrough Listen Search for Intelligent Life: 1.1–1.9 GHz Observations of 692 Nearby Stars

“…Even the most ambitious planned in situ astrobiology missions could only hope to reach the nearest few stars to Earth and would take several dozen years to do so. Remote spectroscopic sensing of the atmospheres of Earth-like exoplanets offers more immediate opportunities, but the extreme difficulty of attaining a sufficiently significant detection of potentially biotic constituents limits this technique to a handful of potential targets out to perhaps 10pc (Segura et al 2005;Rodler & López-Morales 2014;Schwieterman et al 2016). Even for those targets amenable to remote spectroscopic searches for biology, necessary exposure durations with next-generation telescopes (e.g., The James Webb Space Telescope, 8 Thirty Meter Telescope, 9 Giant Magellan Telescope, 10 and the European Extremely Large Telescope 11 ) are measured in days, and detections potentially suffer from confusion with abiotic processes that may give rise to similar signatures.…”