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Hubble Finds First Organic Molecule on an Exoplanet
NASA/ESA/G. Bacon (STScI)
NASA's Hubble Space Telescope (HST) has made the first detection ever of an organic
molecule in the atmosphere of a Jupiter-sized planet orbiting another star. This
breakthrough is an important step in eventually identifying signs of life on a planet
outside our solar system.
The molecule found by Hubble is methane, which under the right circumstances can play
a key role in prebiotic chemistry -- the chemical reactions considered necessary to form
life as we know it.
This discovery proves that Hubble and upcoming space missions, such as NASA's James
Webb Space Telescope, can detect organic molecules on planets around other stars by
using spectroscopy, which splits light into its components to reveal the "fingerprints" of
"This is a crucial stepping stone to eventually characterizing prebiotic molecules on
planets where life could exist," said Mark Swain of NASA's Jet Propulsion Laboratory
(JPL), Pasadena, Calif., who led the team that made the discovery. Swain is lead author
of a paper appearing in the March 20 issue of Nature.
The discovery comes after extensive observations made in May 2007 with Hubble's Near
Infrared Camera and Multi-Object Spectrometer (NICMOS). It also confirms the
existence of water molecules in the planet's atmosphere, a discovery made originally by
NASA's Spitzer Space Telescope in 2007. "With this observation there is no question
whether there is water or not - water is present," said Swain.
The planet now known to have methane and water is located 63 light-years away in the
constellation Vulpecula. Called HD 189733b, the planet is so massive and so hot it is
considered an unlikely host for life. HD 189733b, dubbed a "hot Jupiter," is so close to
its parent star it takes just over two days to complete an orbit. These objects are the size
of Jupiter but orbit closer to their stars than the tiny innermost planet Mercury in our solar
system. HD 189733b's atmosphere swelters at 1,700 degrees Fahrenheit, about the same
temperature as the melting point of silver.
Though the star-hugger planet is too hot for life as we know it, "this observation is proof
that spectroscopy can eventually be done on a cooler and potentially habitable Earth-sized planet orbiting a dimmer red dwarf-type star," Swain said. The ultimate goal of studies like these is to identify prebiotic molecules in the atmospheres of planets in the
"habitable zones" around other stars, where temperatures are right for water to remain
liquid rather than freeze or evaporate away.
The observations were made as the planet HD 189733b passed in front of its parent star
in what astronomers call a transit. As the light from the star passed briefly through the
atmosphere along the edge of the planet, the gases in the atmosphere imprinted their
unique signatures on the starlight from the star HD 189733.
The astronomers were surprised to find that the planet has more methane than predicted
by conventional models for "hot Jupiters." "This indicates we don't really understand
exoplanet atmospheres yet," said Swain.
"These measurements are an important step to our ultimate goal of determining the
conditions, such as temperature, pressure, winds, clouds, etc., and the chemistry on
planets where life could exist. Infrared spectroscopy is really the key to these studies
because it is best matched to detecting molecules," said Swain.
Swain's co-authors on the paper include Gautam Vasisht of JPL and Giovanna Tinetti of
University College, London.
The Hubble Space Telescope is a project of international cooperation between NASA and
the European Space Agency (ESA) and is managed by NASA's Goddard Space Flight Center
(GSFC) in Greenbelt, Md. The Space Telescope Science Institute (STScI)
conducts Hubble science operations. The institute is operated for NASA by the
Association of Universities for Research in Astronomy, Inc., Washington, D.C. JPL
manages the Spitzer Space Telescope for NASA. Scheduled for launch in 2013, JWST
will probe even deeper into the universe than Hubble can now. JWST is an international
collaboration between NASA, ESA, and the Canadian Space Agency (CSA). GSFC is
managing the development effort. The prime contractor is Northrop Grumman Space
Technologies. STScI will operate JWST after launch.
More information on the discovery and artist's concepts are online at:
For more information on this story, contact:
NASA Headquarters, Washington, D.C.
Space Telescope Science Institute, Baltimore, Md.
Space Telescope Science Institute