Extrasolar carbon dioxide
The NASA/ESA Hubble Space Telescope's international team of researchers has discovered carbon dioxide in the atmosphere of a planet orbiting another star, a Jupiter-sized planet called HD 189733b, according to findings published in the Astrophysical Journal Letters, 9 December 2008. This is an important step along the trail of finding the chemical biotracers of extraterrestrial life. New Hubble observations are a proof-of-concept demonstration that the basic chemistry for life can be measured on planets orbiting other stars. Organic compounds can also be a by-product of life processes and their detection on an Earth-like planet may someday provide the first evidence of life beyond Earth. Previous observations of HD 189733b by Hubble and the Spitzer Space Telescope found water vapor. Earlier this year, Hubble found methane in the planet's atmosphere. The team used Hubble's Near Infrared Camera and Multi-Object Spectrometer (NICMOS) to study infrared light emitted from the planet, which lies 63 light-years away. Gases in the planet's atmosphere absorb certain wavelengths of light from the planet's hot glowing interior. They identified not only carbon dioxide, but also carbon monoxide. The molecules leave their own unique spectral fingerprint on the radiation from the planet that reaches Earth. This is the first time a near-infrared emission spectrum has been obtained for an extrasolar planet. This successful demonstration of looking at near-infrared light emitted from a planet is very encouraging for astronomers planning to use the NASA/ESA/CSA James Webb Space Telescope (JWST) when it is launched in 2013. These biomarkers are best seen at near-infrared wavelengths. Astronomers look forward to using JWST to spectroscopically look for biomarkers on terrestrial planets.