Scientists able to analyze distant planet

WASHINGTON -- In an important step in the search for extraterrestrial life, astronomers have made the first direct detection of the chemical composition of the atmosphere of a planet orbiting a distant star. \nScientists focused the Hubble Space Telescope on a star 150 light-years away and found that a planet there contained sodium in its atmosphere. Experts said the achievement demonstrates that it may be possible to search for the chemical signature of life on planets beyond the solar system. \n"Suddenly, discussing searches for Earth-like planets seems quite reasonable," David Charbonneau, an astronomer at the California Institute of Technology, said in a statement. "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." \nThe planet orbits a sun-like star called HD 209458 in the constellation Pegasus, some 150 light-years from Earth. A light-year is the distance light travels in a year, or about 6 trillion miles. The planet is one of 76 that have been found in orbit of distant stars, but it is the first to have its atmosphere chemically analyzed. \nThe planet is about 70 percent the size of Jupiter, the largest planet in the sun's family of satellites, but it orbits just 4 million miles from its parent star. As a result, the planet whips around the star every 3.5 days. In contrast, the Earth is about 93 million miles from the sun and takes a year to complete one orbit. \nEarlier studies by Charbonneau and Timothy Brown of the National Center of Atmospheric Research also showed that the planet was gaseous, like Jupiter, instead of solid, like Earth. \nBecause of the planet's orbital motion and position, Charbonneau and Brown devised a space telescope viewing program that would measure the chemistry of the planet's atmosphere. \nThe astronomers knew that as the planet moved in front of its parent star, light from the star would pass through the planet's atmosphere on its way to the Earth. As its passes through the planet's atmosphere, the spectra of the light is changed by the atmospheric chemicals. By measuring the spectral characteristics of this light using Hubble, Charbonneau and Brown were able to confirm that there is sodium in the planet's atmosphere. \nA National Center of Atmospheric Research statement said the Hubble spectrograph was tuned to detect only sodium. A new observation effort is being planned to search for Earth-like chemicals such as methane, water vapor and potassium.