An 'Astounding Time' for Planetary Discoveries

"There are a hundred billion stars in our galaxy and probably a hundred billion other galaxies with as many stars as ours, so it seems highly unlikely that there are not Earth-like planets orbiting some of them out there, waiting to be discovered," he said. "With that in mind, we're working hard on techniques to answer the question of whether there's life on them to be found."

Some of the work of finding exoplanets and analyzing their orbits and atmospheres is being done with ground-based telescopes, and some from orbiting observatories such as the Hubble Space Telescope, which provided the data used to discover exoplanet methane. In addition, astronomers and astrophysicists are developing ever more powerful ways to interpret data and to use spectroscopy, which splits light into its components to reveal the "fingerprints" of various chemicals.

Considerably more powerful hardware is also on the way. NASA's Kepler satellite, which is designed to find distant planets as they transit in front of their stars, is supposed to be launched next spring and is expected to locate hundreds or thousands of new planets. The James Webb Space Telescope, a high-powered Hubble successor that will be able to find atmospheric molecules in rocky exoplanets rather than only in gas giants, is scheduled for launch in 2013.

The recent discovery of methane in the atmosphere of exoplanet HD 189733b was the kind of breakthrough that the astrobiology institute and many others are looking for -- even though the methane almost certainly has chemical origins, as on Jupiter and Saturn, rather than biological ones. (The planet is punishingly close to its sun -- making a full orbit in two days -- and has an atmospheric temperature of about 1,700 degrees Fahrenheit.) Nonetheless, methane can be a byproduct of biological processes, and so learning how to detect it is essential.

The observations were made as the planet passed in front of its parent star in what astronomers call a transit.

As the light from the star briefly pierced the atmosphere along the planet's edge, atmospheric gases imprinted their identifiable signatures on the starlight.

The astronomers expected to find signs of carbon monoxide on the spectrogram rather than methane, and they were surprised by what they found.

"This indicates we don't really understand exoplanet atmospheres yet," Swain said.

But considering that 15 years ago not a single planet had been discovered outside our solar system, Swain said, it is remarkable that scientists are now probing the makeup and dynamics of planets so far away.

"I think the more we look, the more evidence we'll find that the conditions are out there for life to exist," he said. "I don't see a good reason why our situation in our solar system should be unique. Perhaps uncommon, but not unique."