Does Earth have a faraway sister?

Some Americans may not realize NASA isn’t the only agency pioneering space and announcing new discoveries. The European Space Agency says the COROT space telescope has found the smallest terrestrial planet ever detected outside the Solar System. The ESA said, “The amazing planet is less than twice the size of Earth and orbits a Sun-like star.” Its temperature is so high that it is possibly covered in lava or water vapor. Hundreds of exoplanets have been found, but ESA said most are gas giants and they are similar to planets Jupiter and Neptune. But the new discovery has experts excited because this planet has a surface solid enough to walk upon. The new find, COROT-Exo-7b, also has a diameter less than twice that of Earth and it orbits its star once every 20 hours. It is located very close to its parent star. The new discovery is trillions of miles from Earth.

One of the methods for detecting exoplanets is to look for the drop in brightness they cause when they pass in front of their parent star. Such a celestial alignment is known as a planetary transit. [CNES, French Space Agency, photo]

Compared to Earth, COROT-Exo-7b has a high temperature, between 1000 and 1500°C [1832-2748 degrees F]. Astronomers detected the new planet as it transited its parent star, dimming the light from the star as it passed in front of it. The ESA said terrestrial planets are very hard to detect.

The internal structure of COROT-exo-7b particularly puzzles scientists; they are unsure whether it is an ‘ocean planet’, a kind of planet whose existence has never been proved so far. In theory, such planets would initially be covered partially in ice and they would later drift towards their star, with the ice melting to cover it in liquid.

"This discovery is a very important step on the road to understanding the formation and evolution of our planet," said Malcolm Fridlund, ESA’s COROT Project Scientist. “For the first time, we have unambiguously detected a planet that is 'rocky' in the same sense as our own Earth. We now have to understand this object further to put it into context, and continue our search for smaller, more Earth-like objects with COROT," he added.

COROT (planetary convection, rotation and transits) is a mission led by the French Space Agency (CNES), with contributions from ESA, Austria, Belgium, Germany, Spain and Brazil. It is a telescope placed in Earth orbit that was launched in December, 2006 carrying a 27 cm-diameter telescope designed to detect tiny changes in the brightness of nearby stars. The mission’s main objectives are to search for exoplanets and to study stellar interiors.

The ESA maintains an in-depth website similar to NASA’s website, with resources for the public and educators. Whether Earth has a sister in faraway galaxies is a question that may one day soon be answered.