Exoplanet’s Methane Spotted From Hawaii

A telescope atop Mauna Kea volcano in Hawaii has detected fluorescent infrared emission stemming from methane in the atmosphere of a giant, Jupiter-like extrasolar planet—the first time such a measurement has been made from Earth’s surface (Nature 2010, 463, 637). NASA’s space-based Hubble and Spitzer telescopes, orbiting above Earth’s interfering atmosphere, had been necessary to make such discoveries. For example, these telescopes have already found methane, water, carbon dioxide, and carbon monoxide in this particular planet’s atmosphere. Thanks to new, error-correcting calibration methods developed by an international team led by Mark R. Swain of the Jet Propulsion Laboratory, in Pasadena, Calif., successful ground-based measurements may now become commonplace and complement space-based observations. Swain and coworkers used NASA’s Infrared Telescope Facility (IRTF) on Mauna Kea to observe the planet known as HD189733b, which closely orbits a star 63 light years from Earth. IRTF can observe IR spectral regions not possible with the space-based telescopes, allowing it to record the methane emission from HD189733b’s upper atmosphere.