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The newfound exoplanet Corot-9b and its central star are pictured in an artist's conception.

Ilustration courtesy Instituto de Astrofísica de Canarias

Ker Than

for National Geographic News

Published March 17, 2010

A newly discovered gas-giant planet with a nearly circular orbit around its parent star is the first Jupiter-like planet outside our solar system—or "exoplanet"—that can be studied in detail, a new study says.

Located about 1,500 light-years from Earth in the constellation Serpens, the planet Corot-9b passes in front of its star every 95 days, as viewed from Earth. Each of these "transits" lasts about eight hours.

When Corot-9b is positioned between its star and Earth, some of the light from its star passes through the exoplanet's atmosphere before continuing on to our planet.

By studying this filtered starlight, astronomers may be able to determine what molecules make up Corot-9b's atmosphere.

If that's the case, Corot-9b could become a "Rosetta stone" for exoplanet research, said study co-author Claire Moutou of the Laboratory of Astrophysics of Marseilles in France, referring to the artifact that helped decipher ancient Egyptian hieroglyphics.

(Related: "Distant Planet Mapped for First Time, "Hot Jupiter" Features Fierce Winds.")

"We hope that when we can investigate this planet, it will have characteristics which are close to other giant gas planets outside our solar system," Moutou said.

That's because Corot-9b's physical properties are thought to be representative of many gas giant exoplanets in our galaxy. So studying Corot-9b in detail could shed light on worlds that do not transit, and thus are impossible for astronomers to research.

New Planet Similar to Jupiter and Saturn

The filtered-sunlight technique has been used to study the atmospheric compositions of other gas exoplanets with great success.

However, those planets orbit much closer to their stars than Corot-9b and are thus much hotter.

As a result, these "hot Jupiters" are not thought to be good analogs for low- and moderate-temperature gas giants, which astronomers think make up a large bulk of exoplanets. (Get more facts about the universe.)

In contrast, the distance between Corot-9b and its star is about ten times greater than that of hot Jupiter systems. Its surface temperature is estimated to be between -4 degrees and  320 degrees Fahrenheit (-20 degrees and 160 degrees Celsius).

While no one has seen Corot-9b up close yet, Moutou imagines it looks very similar to the gas giants in our own solar system.

For instance, Corot-9b is probably a gaseous, cloudy planet like Jupiter with lots of moons and rings like Saturn, she said.

The research is detailed in this week's issue of the journal Nature.

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