February 12, 2009

CoRoT discovers “super Earth”

CNES’s space telescope has “unearthed” the smallest exoplanet observed to date. The announcement was made last week at the 1st CoRoT International Symposium in Paris.
9 February 2009

400 light-years away

Astronomers have been waiting for this moment since CoRoT first ventured into space in 2006. CNES’s space telescope has just discovered the 1st telluric exoplanet: a sort of “super Earth” with a diameter only twice that of our planet.

In fact, “sauna planet” might be a better description, since the temperature on its surface is between 1,000 and 1,500°C.

The object orbits very close to its parent star Corot-Exo-7, taking only 20 hours to complete one orbital revolution versus one year for Earth around the Sun.

The new exoplanet, dubbed CoRoT-Exo-7b, has been greeted enthusiastically by the scientific community, although the discovery is not really a surprise.

“CoRoT-Exo-7b belongs to a class of objects whose existence had been predicted for some time. CoRoT was designed precisely in the hope of discovering some of these objects,” explains Daniel Rouan from the LESIA* space and astrophysics instrumentation research laboratory at the Paris Observatory.

The hunt for planets harbouring life

Astronomers observed 153 transits of the planet over a period of 5 months, then waited 1 year before making an announcement to give themselves time to verify their find using large ground-based telescopes.

“You can imagine our excitement each time a new measurement came in,” says Alain Léger at the IAS space astrophysics institute in Paris. The planet’s mass has not yet been determined precisely but is thought to be less than 11 times that of Earth..

Its density is even less well determined: the object could be a rocky planet like Earth, covered in liquid lava. Or it could be an “ocean planet”, a class of object formed of 50% water and 50% rock whose existence has been predicted but not yet proven.

Scientists will now continue investigating the data from the spacecraft to gain a closer understanding of the inner structure of Earth’s cousin CoRoT-Exo-7b.

Les astronomes ont observé 153 passages de la planète devant son étoile pendant 5 mois, puis ont attendu un an avant d'annoncer la découverte, le temps de vérifier avec les grands télescopes terrestres qu'il s'agissait bien d'une exoplanète.

Animation du système planétaire dans lequel se trouve CoRoT-Exo-7b. Crédits : CNES 2009.

“We believe this discovery by the CoRoT spacecraft is a key step along the trail that could lead us to planets able to support life,” concludes Alain Léger.



CoRoT-exo-7b - Basic data
Name : CoRoT-Exo-7b
Parent star : CoRoT-Exo-7
Features : a “super Earth”, a rocky planet covered in liquid lava or an ocean planet (50% rock, 50% water)
Location : the Unicorn constellation, 400 light-years from the solar system
Radius : 1.75 and 2 Earth radii
Mass not well determined, less than 11 times that of Earth
Orbital period : 0.85 days or 20 hrs
Surface temperature : 1,000 to 1,500°C

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