Finding a Second Earth

DW-WORLD.DE: How did you discover the planet? Was it a coincidence?

Stephane Udry: No, of course not. We're working on a complete research project to discover such planets. We're tracking several thousand stars to get hints about planets from them. Our planet circles around a home star. We're mainly interested in the traveling speed of such stars, because it helps us to calculate the existence of a planet.

What's the name of the planet?

We don't name them, because there are too many of them. We're using the name of the home star and add a letter that references the date of discovery. The first planet that's discovered around a star gets a "B," the second a "C." The new planet is called Gliese 581 C, because it's the second that we've discovered near the star Gliese 581.

What kind of conditions exist on Gliese 581 C?

That's a difficult questions. It probably has a hard surface structure, because that's the case with most planets of this size. The mass of our planet is five times as big as that of the Earth. The average temperature should be between 0 and 40 degrees Celsius (32 and 104 degrees Fahrenheit.) A year only lasts 13 days on the planet, because it circles near its star.

Does organic life maybe exist there?

I can only say that the size and the temperature of the planet would be good for that. The planet is in the so-called habitable zone, because it's highly probable that water exists there. There are probably several sources of water. There are probably comets that bring water to the planet, as happened on Earth during the early phase of the solar system. There could be ice. But the basic requirements for life are chemical components such as carbon and oxygen. If they exists, conditions are good. But I cannot say much at the moment. It's possible that we'll be able to do so in 20 years. We need light from the planet's atmosphere to determine that.

Can you use research probes to examine the planet further?

No, it's too far away for that -- 20 light years. If we could travel at one tenth of the speed of light, which would be wonderful, we'd still need two centuries to get there. That's why we have to continue to analyze the information from here.

How important is this discovery for science?

It's certainly an important discovery. Our long-term goal is to find a second planet, where life is possible. We're trying to find a second "Earth" step by step.