Finding Extraterrestrial Life Using Ground-based High-dispersion Spectroscopy

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Finding Extraterrestrial Life Using Ground-based High-dispersion Spectroscopy

Type: Article / Letter to editor
Title: Finding Extraterrestrial Life Using Ground-based High-dispersion Spectroscopy
Author: Snellen, I.A.G.Kok, R.Poole, R.S. leBrogi, M.Birkby, J.L.
Journal Title: The Astrophysical Journal
Volume: 764
Start Page: 182
Issue Date: 2013
Abstract: Exoplanet observations promise one day to unveil the presence of extraterrestrial life. Atmospheric compounds in strong chemical disequilibrium would point to large-scale biological activity just as oxygen and methane do in the Earth's atmosphere. The cancellation of both the Terrestrial Planet Finder and Darwin missions means that it is unlikely that a dedicated space telescope to search for biomarker gases in exoplanet atmospheres will be launched within the next 25 years. Here we show that ground-based telescopes provide a strong alternative for finding biomarkers in exoplanet atmospheres through transit observations. Recent results on hot Jupiters show the enormous potential of high-dispersion spectroscopy to separate the extraterrestrial and telluric signals, making use of the Doppler shift of the planet. The transmission signal of oxygen from an Earth-twin orbiting a small red dwarf star is only a factor of three smaller than that of carbon monoxide recently detected in the hot Jupiter {$τ$} Boötis b, albeit such a star will be orders of magnitude fainter. We show that if Earth-like planets are common, the planned extremely large telescopes can detect oxygen within a few dozen transits. Ultimately, large arrays of dedicated flux-collector telescopes equipped with high-dispersion spectrographs can provide the large collecting area needed to perform a statistical study of life-bearing planets in the solar neighborhood.

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