Detection of Earth-like Planets with Large Telescopes
Using large space-based telescopes (>10-meter) Astronomers could search for terrestrial planets with atmospheres suitable for life as we know it. Spectroscopy could be used to detect the presence of Ozone, an indicator of oxygen in the atmosphere as well as water bands. Methane produced as a result of biogenic activity could be searched for using the same methods.
Using telescopes in Earth orbit planets could be searched for using direct detection methods. Stellar coronagraphs can be used to supress the light from the planet's parent star making detection easier. There is a higher probability of detecting planetary companions around nearby stars in the infrared portion of the electromagnetic spectrum. This is due to the fact that the star to planet flux ratio is less in this region of the spectrum than in the visible.
To separate a planetary companion from its primary stellar halo, one must use a telescope (or array of telescopes) with an aperture (or baseline) B such that r/D is greater than or equal to the wavelength at which the observation is being carried out divided by the aperture (or baseline) of the telescope (or array of telescopes).
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