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The Sciences

Temperate, Jupiter-Sized World Resembles the Planets of Our Solar System



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It’s the size of Jupiter, orbits at about the distance of Mercury, and isn’t too far from the temperature range of Earth. Meet Corot-9b, the newest find in the cavalcade of exoplanets and the one its discoverers say is most like the worlds of our own solar system.

“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” []. The large group of astronomers reporting the find in Nature estimate the planet’s temperature at a range between just below zero and slightly above 300 degrees Fahrenheit. It completes an orbit in 95 days, though it’s about 1,500 light years away.

The new exoplanet draws its name from the French space agency’s Corot (Convection, Rotation and planetary Transits) satellite, which first spotted it by noticing its star dim as the planet passed in front. Actually confirming a planetary cause of that dimming takes painstaking follow-up work at telescopes on the ground. Most often the researchers look for Doppler shifts in the host star’s light as the planet’s gravity regularly tugs the star nearer to and then farther from Earth [Scientific American]. Back in September, the Corot satellite also was the first to find Corot-7b, which was the first exoplanet discovered to be close to the Earth in size.

Determining Corot-9b’s distance from its star and the type of that star allowed the team, led by Hans Deeg, to hypothesize that the planet’s temperature range is close to that of Earth’s. But is it a pale blue dot like our own home world? “We don’t know the colour. It’s likely that it has high atmosphere water clouds which might make it blue but that depends on the mixture of gases which we really do not know” [BBC News], Deeg says.

Image: Ilustration courtesy Instituto de Astrofísica de Canarias

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