Observing Exoplanet Atmospheres From the Ground

In the 15 years since the first planet orbiting a sunlike star outside our solar system was conclusively discovered, astronomers have compiled a vast and diverse menagerie of such so-called exoplanets. Of the more than 400 now known, many are large—10 times the mass of Jupiter or more—and a precious few are small, just a few times Earth's mass. Little is known about these faraway worlds beyond bulk properties such as their orbital periods, estimated masses and, on relatively rare occasions, their diameters.

As instrumentation and observation techniques have become more sophisticated over the past few years, exoplanet researchers have begun probing the nature of these bodies more deeply, even identifying specific molecules in their atmospheres. Someday, detailed observations of exoplanet atmospheres might allow astronomers to pinpoint worlds where life seems to have taken hold, producing, for instance, otherwise unexplainable cocktails of oxygen and methane.

But although many planets are first discovered using telescopes on the ground, most of the spectroscopic measurements that have afforded astronomers a glimpse at their atmospheres have come from space-based observatories such as the Hubble and the Spitzer space telescopes, which operate outside the obscuring veil of Earth's own atmosphere. (Telescope spectrographs break down the light coming from a celestial object into its individual wavelengths, allowing the identification of atoms or molecules by their unique emission or absorption properties.)

In a paper published in the February 4 issue of Nature, a team of researchers from the U.S., England and Germany demonstrates the ability of moderate-size telescopes on the ground to identify the chemical fingerprints in exoplanet atmospheres. …

See Scientific American - Extraterrestrial Life for links to further info.