Detecting Life-bearing Extra-solar Planets with Space Telescopes

TL;DR

Detecting signs of life on exoplanets via space telescopes requires large, 10-meter class or bigger telescopes to effectively analyze atmospheric signatures like oxygen and methane.

Contribution

This paper analyzes the technical requirements and sample sizes for space telescopes to detect biosignatures on exoplanets, emphasizing the need for very large telescopes.

Findings

Coronagraph-based detection benefits greatly from larger telescope diameters.

Sample size for atmospheric biosignature detection scales with telescope size.

Large telescopes (around 10m or more) are necessary for effective life detection on exoplanets.

Abstract

One of the promising methods to search for life on extra-solar planets (exoplanets) is to detect life's signatures in their atmospheres. Spectra of exoplanet atmospheres at the modest resolution needed to search for oxygen, carbon dioxide, water, and methane will demand large collecting areas and large diameters to capture and isolate the light from planets in the habitable zones around the stars. For telescopes using coronagraphs to isolate the light from the planet, each doubling of telescope diameter will increase the available sample of stars by an order of magnitude, indicating a high scientific return if the technical difficulties of constructing very large space telescopes can be overcome. For telescopes detecting atmospheric signatures of transiting planets, the sample size increases only linearly with diameter, and the available samples are probably too small to guarantee detection of life-bearing planets. Using samples of nearby stars suitable for exoplanet searches, this paper shows that the demands of searching for life with either technique will require large telescopes, with diameters of order 10m or larger in space.