"Our Job is to Find Another Earth"
3 May, 2007 12:05 pm
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Send this articleSt?phane Udry is the lead-author of a study issued last week reporting the finding of a habitable Earth-like planet. He answers Scitizen?s questions.
Can you describe this world?
What we know from our measurements is a separation between the planet and the star and the mass of the planet. The mass is about five times the mass of the Earth and about 1.5 to 2 times the size of the Earth. It’s not that big. The separation between the planet and the star is just right for the temperature to be around 20° C, so there could be water on the surface of the planet in liquid form and hence it could be habitable.
There could be extraterrestrial life on this planet. How can this be investigated?
The possibility of having life is, of course, related to the presence of water, and the main building blocks of life, the chemical components used to build life like carbon, oxygen nitrogen, that are available everywhere in the universe because they’re formed in the stars. So we have everything there for life to start, but we don’t know if it did start. There are projects of space mission in the future that will look for traces of life in the atmosphere of extrasolar planets. The idea is to send a satellite in space, and then put a mask in front of the stars so you do not have the light of the stars that is blowing your view. Then you hide the light of the stars, and you may see the planet next to the star. If you see the planet, you can start to analyse the chemical composition of the atmosphere of the planet, because light is coming from the atmosphere of the planet. If there is a trace of oxygen in the atmosphere, that would mean there is life on that planet. To do that you would first have to build the instrumentation, and it could take maybe 20 to 30 years from now on.
Are you talking about the Darwin telescope?
There is the Darwin project by the Europeans and there is a similar one called TPF by NASA.
How did you detect this planet?
Our work consists in detecting extrasolar planets by the measurement of the velocity of stars. We follow the velocity of the stars in time, and if there’s a planet, the planet will pull the star a little bit and you will see a change in the velocity of the star. The bigger the planet, the larger the change in the star’s velocity. For twelve years now our group has found about 100 extrasolar planets, in collaboration with French teams and also American, Portuguese, and Israeli ones. Also, for 3 years we improved a lot our capacity in detecting small mass planets with the installation of a new instrument in Chile (HAPS). That’s the most precise in the world.
Are you confident that the discovery of a planet with a comparable mass to that of the Earth is within reach?
That’s our main goal. Our job is to find another Earth around another star like the sun. We still have to improve our precision in the measurements, and we are now developing the instrumentation to do that. Of course, the planet we've just detected has a mass five times the mass of the Earth, and is orbiting a star that is smaller than the Earth's. So far it’s easier to detect bigger planets around smaller mass stars. That’s what we’re doing, but it’s just a first step toward a real Earth. That could be possible in 10 years from now on.
What sort of life would you expect to find on this kind of planet?
It’s very difficult to say, because if the location is such that temperature could be around 20°C, then the composition and the thickness of the atmosphere is not known. You could have green house effect increasing the temperature to high values, or maybe there isn't any atmosphere. So you can’t develop life. Or you may have lots of water and oceans around the planet. So you may have everything between bacteria and whales.
Stephane Udry, how do one feel when discovering a new world?
As I have said, we’ve found before, in our group and with our collaborators of other countries, about half of the known exoplanets, including the first one twelve years ago. This one is a special one, because water could exist on it. As I also mentioned, the aim of the whole work is to find another Earth. We're just in between as we’re going slowly.
It's like when you have worked well during one day, and in the evening you just rest on the coach and you’re happy having done a good job. We also know that tomorrow we’ll have to start again, and go on with the work. So there’s no special excitement, just the feeling of satisfaction.
Interview by Clementine Fullias
Stephane Udry works at the Geneva Observatory (Switzerland).
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