The world is far hotter than ours, however.
Astronomers used the COROT space telescope (a mission led by the French Space Agency) to detect the
new planet as it transited its parent star, dimming the light from the star as it passed in front of it."For the first time, we have unambiguously detected a planet that is 'rocky' in the same sense as our own Earth," said Malcolm Fridlund, ESA's COROT Project Scientist. "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, "This discovery is a very important step on the road to understanding the formation and evolution of our planet."
Hot discovery
One big difference in the newfound planet compared to Earth: COROT-Exo-7b is located very close to its star, orbiting the star once every 20 hours. Its temperature is so high, ranging from 1,832 to 2,732 degrees Fahrenheit (1,000 to 1, 500 degrees Celsius) that the researchers say the exoplanet could be covered in lava or water vapor.
The density of the planet is still under investigation, though scientists say it may be rocky like Earth and covered in liquid lava. COROT-Exo-7b may also belong to a class of planets that are thought to be made up of water and rock in almost equal amounts. Given the high temperatures measured, the planet would likely be a very hot and humid place.
"Finding such a small planet was not a complete surprise," said Daniel Rouan, researcher at the Observatoire de Paris Lesia, who coordinates the project with Alain Leger, from Institut d'Astrophysique Spatiale. "COROT-Exo-7b belongs to a class of objects whose existence had been predicted for some time."
Small and odd
Very few of the more than 300 exoplanets found so far have a mass comparable to that of Earth and the other terrestrial planets — Venus, Mars and Mercury. That's because terrestrial planets are extremely difficult to detect.
Most of the methods used so far are indirect and sensitive to the mass of the planet, so bigger worlds are easier to detect. COROT can directly measure the size of a planet's surface, which is an advantage to astronomers. In addition, because the probe is in space it has longer periods of uninterrupted observation than from ground.
The internal structure of COROT-exo-7b particularly puzzles scientists, as 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 toward their star, with the ice melting to cover it in liquid.
