A planetary system around a star named CoRoT-7 is home to the first solid, rocky planet discovered by astronomers. The star is named for the CoRoT (Convection Rotation and planetary Transits) satellite, which is the first spacecraft designed solely for extrasolar planetary detection.
Facts about the Planetary System around CoRoT-7
CoRoT-7 is the first star known to have a planetary system made of two short period super-Earths. One of these planets transits the star, which has allowed astronomers to measure the planet's mass. The star lies 500 light-years away in the direction of the constellation Monoceros the Unicorn. CoRoT-7 is smaller and cooler than our Sun and about 1.5 billion years old, compared to the Sun's age of 4.5 billion years. CoRoT-7 has two planets that are categorized as super-Earths; so far only about a dozen such planets have been discovered. Super-Earths are those planets which are not gas giants such as Jupiter of Saturn but are still up to 10 Earth masses larger than Earth.
The two planets around CoRoT-7 have been named CoRoT-7b and CoRoT-7c. CoRoT-7c is less well understood because it does not transit directly in front of its star to allow for precise measurements. What is known about CoRoT-7c is that the planet orbits its star in three days and 17 hours and has a mass eight times that of Earth.
CoRoT-7b Was the First Rocky Exoplanet Discovered
CoRoT-7b is the smallest and fastest-orbiting exoplanet yet discovered. Its tiny orbit, at 23 times closer to its star than Mercury is to the Sun, makes it the closest known exoplanet to its host star, at a distance of just 2.5 million kilometers. The smaller the orbit, the faster the planet circles its star, and therefore CoRoT-7b travels at more than 750,000 kilometers per hour.
"CoRoT-7b is so close that the place may well look like Dante's Inferno, with a probable temperature on its 'day-face' above 2,000 degrees and minus 200 degrees on its night face. Theoretical models suggest that the planet may have lava or boiling oceans on its surface. With such extreme conditions this planet is definitively not a place for life to develop," says Didier Queloz, who led the team that made the CoRoT-7b discoveries.
Astronomers have been able to measure the planet's radius and mass. Its radius is about 80 percent greater than that of Earth, which allowed its mass to be calculated at about five times that of Earth. Therefore, CoRoT-7b's density is close to that of Earth, revealing the first known rocky, solid world outside our solar system. CoRoT-7b is the lightest exoplanet yet found.
The image shown here is an artist's impression of the star CoRoT-7 with its possible lava-covered planet CoRoT-7b in the foreground and CoRoT-7c in the background.
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