CNES Space Telescope Finds Familiar Exoplanet

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The French planet-hunting telescope Corot recently discovered an exoplanet that researchers said March 17 is the first such alien world to resemble the planets in our solar system.

The planet, dubbed Corot-9b, was found to be about the size of Jupiter and situated at an orbit similar to Mercury, which is the innermost planet in our solar system.

While that seems close, it is much farther away than other gas giant planets found around alien stars with the exoplanet detection method used in the new study. This distance, in turn, means that Corot-9b has a more temperate climate than other gas giants — so-called hot Jupiters — that can experience radical temperature swings.

The research team also thinks that the planet has an interior composition similar to that of Jupiter and Saturn.

“Like our own giant planets, Jupiter and Saturn, the planet is mostly made of hydrogen and helium,” said team member Tristan Guillot of the Côte d’Azure Observatory in Nice, France. “And it may contain up to 20 Earth masses of other elements, including water and rock at high temperatures and pressures.”

Launched by the French space agency CNES in December 2006, the Corot space telescope detected the telltale light signature of the planet transiting — or passing in front of — its host star from the perspective of Earth. Because it transits in front of its parent star for about eight hours, astronomers are able to learn a good deal about the planet.

“Our analysis has provided more information on Corot-9b than for other exoplanets of the same type,” said Didier Queloz of the Observatory of the University of Geneva in Switzerland, one of the astronomers on the team that discovered the planet.

One thing that makes Corot-9b such an important find is that its distance from its parent star is about 10 times greater than any other planet previously discovered with this transiting method.

It also has a low eccentricity orbit, compared with many other exoplanet gas giants discovered so far, which means that its distance from its star does not vary wildly like that of other exoplanets. It is that stable distance that allows Corot-9b’s more temperate climate, researchers said.

The team that reported the discovery of the planet in the March 18 issue of the journal Nature estimates that Corot-9b’s surface temperature is between minus-20 degrees and 160 degrees Celsius, with small differences between its day and night sides.