[Artist’s view of exoplanet orbiting the star HD 189733. Image credit: ESA, NASA, M. Kornmesser (ESA/Hubble), and STScl.] It’s more than likely too close to its star, and far too hot, to sustain life but the Jupiter-sized exo-planet HD 189733b is proving to be an intriguing study – and, at 63 light-years away, over twice the distance to Fomalhaut b. As mentioned here, earlier this year Hubble was used to identify the organic molecule methane in its atmosphere and the Spitzer Space Telescope has also detected water vapour there. Now further observations by the Hubble Space Telescope have discovered carbon dioxide in the exo-planet’s atmosphere.
This successful demonstration of looking at near-infrared light emitted from a planet is very encouraging for astronomers planning to use NASA’s James Webb Space Telescope after it is launched in 2013. These biomarkers are best seen at near-infrared wavelengths. Astronomers look forward to using the Webb telescope to look spectroscopically for biomarkers on a terrestrial planet the size of Earth or a “super-Earth” several times our planet’s mass.
Although [NASA] is keen to stress the planet is far too hot to support life, it says the finding represents an important proof of concept, showing that it is possible to detect CO2 in the atmospheres of distant planets orbiting other stars, and that the same method could be used to look at planets which might support life.
“The very fact we are able to detect it and estimate its abundance is significant for the long-term effort of characterising planets to find out what they are made of and if they could be a possible host for life,” said Mark Swain, a research scientist at Nasa’s Jet Propulsion Laboratory in Pasadena, California, who analysed the Hubble images.