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Atmosphere detected on distant planet

Artist's concept of giant planet around HD 209458, a star 150 light-years away
Artist's concept of giant planet around HD 209458, a star 150 light-years away  

By Richard Stenger
CNN Sci-Tech

(CNN) -- Scientists for the first time have detected an atmosphere on a planet outside our solar system, using NASA's flagship orbiting observatory.

The observation suggests that the planet, which is almost as massive as Jupiter, has an atmosphere similar to gas giants in our solar system, researchers said.

The same technique could be refined to scrutinize other planets for the kinds of gases consistent with the presence of life.

"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," lead scientist David Charbonneau said Tuesday.

The planet is located around a sun-like star about 150 light-years away in the constellation Pegasus. It is one of about 80 planets discovered beyond our solar system in recent years.

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The so-called planets tug slightly on their parent stars as they orbit, creating gravitational variations that allow scientists to estimate their masses and orbital paths.

Unlike the others, this planet passes right in front of its star, relative to the line-of-sight from Earth.

The unique vantage allowed scientists to make direct observations of the planet as it filtered the light from its parent star.

The research team found that the planet's atmosphere possesses atomic sodium, a common chemical on Jupiter.

"We saw only half as much (sodium) absorption as we expected," said scientist Timothy Brown. "It shows that the models are close to right but not exactly right."

He called the observation "reassuring," however, in that it demonstrated that extrasolar planets could resemble those in our solar system.

Unexpectedly, Charbonneau and colleagues made the discovery using the Hubble Space Telescope, an orbiting observatory hardly suited to study the makeup of distant planets.

"I never thought that Hubble would be able to do it," said Bruce Margon, an astronomer and NASA advisor.

Nevertheless, Hubble scientists plan more observations to look for other chemicals on the planet.

And with NASA planning to launch more powerful space observatories later this decade, astronomers hope eventually to search extrasolar planets for chemicals such as methane, water vapor and carbon dioxide.

By finding high levels of atmospheric gases consistent with the presence of life, such discoveries could offer the first direct evidence of extraterrestrial beings, according to scientists.

Chances are slim that this extrasolar planet harbors life as we know it. Because it orbits only 4 million miles from its parent star, its atmosphere sizzles at 2,000 degrees Fahrenheit (1,100 degrees Celsius).

"If you visited, the first thing that would happen is the change in your pockets would melt," one NASA astronomer joked.


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