Solid evidence for Earthlike rocky planet

European astronomers have found the first solid evidence for a rocky planet outside our own solar system, they revealed today. Observations have confirmed that the new world, dubbed Corot-7b, is the most Earthlike yet found.

Earthlike world
Picture: An artist’s impression of the Earthlike world close to its parent star. (Credit: ESO).

It is less than twice the diameter of our own planet and has a similar density.

But there the resemblance ends. Corot-7b lies so close to its own sun that its surface must be like a vision of hell. Temperatures soar above 2,000 degrees on its day side and sink to minus 200 degrees on the night side.

It means the surface could be covered with molten lava or boiling oceans and it certainly could not hold any form of life as we know it.

Corot-7b is 23 times closer to its parent star than inner planet Mercury is to our own sun, and it zips around it at 750,000 km per hour making its year – the time it takes to complete one orbit – just 3 days 17 hours long.

Didier Queloz, leader of the European team that made the observations from the European Southern Observatory in Chile, said: “This is science at its thrilling and amazing best. We did everything we could to learn what the object discovered by the CoRoT satellite looks like and we found a unique system.”

The Earthlike world was detected in February 2009 by a planet-hunting spaceprobe called Corot. It was spotted around an otherwise unremarkable star named TYC 4799-1733-1 in the constellation of Monoceros, the Unicorn, about 500 light-years away. The star is slightly smaller and cooler than our own sun and only about 1.5 billion years old.

Corot detected the planet by spotting a dip in starlight when it passed in front of its own sun ocne every orbit. To obtain precise data to reveal the planet’s nature they used a device called the High Accuracy Radial velocity Planet Searcher (HARPS) spectrograph attached to the ESO 3.6-metre telescope at the La Silla Observatory in Chile.

The studies also disclose that a second super-Earth lies in the same alien solar system . It does not pass in front of the star but made its presence known by its gravitational pull. It circles its host star in 3 days and 17 hours and has a mass or “weight”, about eight times that of Earth.

• Discover space for yourself and do fun science with a telescope. Here is Skymania’s advice on how to choose a telescope. We also have a guide to the different types of telescope available.

Paul Sutherland

Paul Sutherland

I have been a professional journalist for nearly 40 years. I write regularly for science magazines including BBC Sky at Night magazine, BBC Focus, Astronomy Now and Popular Astronomy. I have also authored three books on astronomy and contributed to others.
Paul Sutherland

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Paul Sutherland

I have been a professional journalist for nearly 40 years. I write regularly for science magazines including BBC Sky at Night magazine, BBC Focus, Astronomy Now and Popular Astronomy. I have also authored three books on astronomy and contributed to others.

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