>Date: Tue, 27 Nov 2001 12:10:18 -0500 (EST) >From: [EMAIL PROTECTED] >Subject: HUBBLE MEASURES ATMOSPHERE ON WORLD AROUND ANOTHER STAR >Sender: [EMAIL PROTECTED] >To: undisclosed-recipients:; > >Donald Savage >Headquarters, Washington Nov. 27, 2001 >(Phone: 202/358-1547) > >Nancy Neal >Goddard Space Flight Center, Greenbelt, Md. >(Phone: 301/286-0039) > >Ray Villard >Space Telescope Science Institute, Baltimore >(Phone: 410/338-4514) > >RELEASE: 01-232 > >HUBBLE MEASURES ATMOSPHERE ON WORLD AROUND ANOTHER STAR > > Astronomers using NASA's Hubble Space Telescope have >made the first direct detection and chemical analysis of the >atmosphere of a planet outside our solar system. Their unique >observations demonstrate it is possible with Hubble and other >telescopes to measure the chemical makeup of extrasolar >planets' atmospheres and potentially to search for chemical >markers of life beyond Earth. > >The planet orbits a yellow, Sun-like star called HD 209458, a >seventh-magnitude star (visible in an amateur telescope) that >lies 150 light-years away in the autumn constellation >Pegasus. Its atmospheric composition was probed when the >planet passed in front of its parent star, allowing >astronomers for the first time ever to see light from the >star filtered through the planet's atmosphere. > >Lead investigator David Charbonneau of the California >Institute of Technology, Pasadena, and the Harvard- >Smithsonian Center for Astrophysics, Cambridge, Mass.; >Timothy Brown of the National Center for Atmospheric >Research, Boulder, Colo.; and colleagues used Hubble's >spectrometer (the Space Telescope Imaging Spectrograph, or >STIS) to detect the presence of sodium in the planet's >atmosphere. > >"This opens up an exciting new phase of extrasolar planet >exploration, where we can begin to compare and contrast the >atmospheres of planets around other stars," says Charbonneau. >The astronomers actually saw less sodium than predicted for >the Jupiter-class planet, leading to one interpretation that >high-altitude clouds in the alien atmosphere may have blocked >some of the light. The team's findings are to be published in >the Astrophysical Journal. > >The Hubble observation was not tuned to look for gases >expected in a life-sustaining atmosphere (which is improbable >for a planet as hot as the one observed). Nevertheless, this >unique observing technique opens a new phase in the >exploration of exoplanets, or extrasolar planets, say >astronomers. Such observations could potentially provide the >first direct evidence for life beyond Earth by measuring >unusual abundances of atmospheric gases caused by the >presence of living organisms. > >The planet was discovered in 1999 through its slight >gravitational tug on the star. The planet was estimated to be >70 percent the mass of the giant planet Jupiter, or 220 times >more massive than Earth. Subsequently, astronomers discovered >that the tilt of the planet's orbit makes it pass in front of >the star -- relative to our line-of-sight from Earth -- >making it unique among all the approximately 80 extrasolar >planets discovered to date. As the planet passes in front of >the star, it causes the star to dim very slightly for the >duration of the transit. Transit observations by Hubble and >ground-based telescopes confirmed that the planet is >primarily gaseous, rather than liquid or solid, meaning that >the planet is a gas giant, like Jupiter and Saturn. > >The planet is an ideal target for repeat observations because >it transits the star every 3.5 days -- which is the extremely >short time it takes the planet to whirl around the star at a >distance of merely four million miles from the star's >surface. This close proximity heats the planet's atmosphere >to a torrid 2,000 degrees Fahrenheit (1,100 degrees Celsius). > >Observations of four separate transits were made by Hubble in >search of direct evidence of an atmosphere. During each >transit a small fraction of the star's light on its way to >Earth passed though the planet's atmosphere. When the color >of the light was analyzed by STIS, the telltale "fingerprint" >of sodium was detected. Though the star also has sodium in >its outer layers, STIS precisely measured the added influence >of sodium in the planet's atmosphere. > >The team, including Robert Noyes of the Harvard-Smithsonian >Center for Astrophysics and Ronald Gilliland of the Space >Telescope Science Institute in Baltimore, plans to look at HD >209458 again with Hubble in other colors of the star's >spectrum to see which are filtered by the planet's >atmosphere. They hope eventually to detect methane, water >vapor, potassium and other chemicals in the planet's >atmosphere. Once other transiting giants are found in the >next few years, the team expects to characterize chemical >differences among the atmospheres of these planets. > >The Space Telescope Science Institute (STScI) is operated by >the Association of Universities for Research in Astronomy, >Inc. (AURA), for NASA, under contract with the Goddard Space >Flight Center, Greenbelt, Md. The Hubble Space Telescope is a >project of international co-operation between NASA and the >European Space Agency (ESA). The National Center for >Atmospheric Research is sponsored primarily by the National >Science Foundation. > > -end- >NOTE TO EDITORS: Electronic images, illustrations, animations >and additional information are available at: >http://oposite.stsci.edu/pubinfo/pr/2001/38 >and via links in >http://oposite.stsci.edu/pubinfo/latest.html >http://oposite.stsci.edu/pubinfo/pictures.html >http://hubble.stsci.edu/go/news > > > * * * > >NASA press releases and other information are available automatically >by sending an Internet electronic mail message to [EMAIL PROTECTED] >In the body of the message (not the subject line) users should type >the words "subscribe press-release" (no quotes). The system will >reply with a confirmation via E-mail of each subscription. A second >automatic message will include additional information on the service. >NASA releases also are available via CompuServe using the command >GO NASA. 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