Hubble Spots CO2 on Extrasolar Planet

Add carbon dioxide to the atmospheric brew enveloping a Jupiter-sized planet orbiting a star about 65 light-years from Earth.
The finding, made by astronomers using an infrared sensor on the Hubble Space Telescope, doesn't do anything to improve the odds of finding life on HD 189733, which also contains methane, carbon monoxide and water in its atmosphere.
The planet orbits too close to its mother star to have temperatures that would be conducive for life as we know it. But scientists are hailing the discovery as further proof that Earth-orbiting spacecraft can pry out secrets of planets beyond our solar system.
"It's a one-part-in-a-thousand kind of measurement," Carl Grillmair, associate research scientist at California Institute of Technology's Spitzer Science Center, told Discovery News.
"HD 189733 is an interesting, exotic test bed for what we want to do with habitable planets down the road," he added. "If you did this same kind of experiment looking at Earth from 65 light-years, it would be 25,000 times dimmer, so it's a much, much harder problem."
Mark Swain, a researcher with NASA's Jet Propulsion Laboratory in Pasadena, Calif., and colleagues hadn't been looking for carbon dioxide in the atmosphere of HD 189733, a planet fortuitously aligned, relative to Earth, so that it passes both in front of and behind the parent star. They were seeking additional measurements of the previously discovered methane.
The planet's eclipses -- it passes behind its sun once every 2.2 days -- provide scientists an opportunity to make the subtle distinction of which light is coming from the planet in the face of the overwhelming brightness of the star. Within the beams are features, similar to fingerprints, of what molecules the light has encountered.
"By using the primary and the secondary eclipse, we're actually localizing knowledge about the atmosphere over specific parts of the planet," Swain told Discovery News.
Some molecules, like carbon dioxide and methane, show up in infrared light. Others, such as oxygen, would leave their footprints in visible or ultraviolet wavelengths.
"The science of exoplanets is driven by what we can do, not what we want to do," Grillmair said. "There's not a lot of data and an abundance of possibilities and ideas, but that shouldn't stop us from pursuing observations with what we have."
"Maybe next week somebody will come up with some molecule that really shouldn't be there. That gives us a hold on the piece of the physics that we didn't have before," he added. "It's always nice to find the unexpected because sometimes it can involve really interesting paradigm shifts."
Swain's research will be published in Astrophysical Journal Letters. Grillmair and colleagues are publishing additional findings of water in HD 189733's atmosphere in this week's Nature.