"It was discovered the first habitable planet", revels Michel Mayor, the Observatory of Geneva. The finer Bloodhound of exoplanets has caught a beautiful prey with five European laboratories, including three French. A month ago, they located a planet outside solar system which is similar to the Earth and could theoretically allow life. Is still far from there to move it is 20.5 years light home, but his profile seduced many researchers.
On modeling of scientists, its very moderate mass is equivalent to 5 times that of Earth. The weakness of this mass means that it has a rocky soil or sea of water, unlike most 220 giant and gaseous exoplanets already identified. It differs primarily from the recent discoveries of planets by its good distance with his star, the red dwarf GI581. Small that our Sun, the radiator is not too far or too close, it offers a comfortable exhibition. "From our calculations, it is between 0 and 40 degrees Celsius, which is compatible with liquid water." "But we do not yet know too much to refine local climatology, which depends on the reflectivity of soil and a possible atmospheric greenhouse effect," explains Michel Mayor.
The authors of the article, published today in "Astronomy and Astrophysics", now collect eleven of the thirteen planets that weigh less than 20 Earth masses. It is among these small bodies that it hopes to find the perfect exoTerre, from our planet's twin sister. Astronomers have abandoned several years hoping to find a life evolved in the solar system. The bodies are either too big, and therefore gaseous, like Jupiter, or too small as the Moon, the insufficient gravity prevented the retention of the atmosphere. Three equivalent to Earth planets mass turning periphery much too far from the Sun for liquid water. On Venus, too close, no body is there withstand the oppressive heat.
Exoplanets teams now focus a significant part of their comments on the smaller planetary systems. Europeans benefit on the subject of an important access to 100 nights in a telescope of the European Southern Observatory (ESO) based in the Chile. They also designed a sensor particularly sharpened for this type of cosmic object. The spectrograph measure the radial velocities of stars with the same principle as radar road. Since the size of exoplanets is too weak to see directly. "It is as if it was seeking a Firefly near a car headlight lit," notes John Trauger, a Nasa astronomer. Astronomers record rather the change in the trajectory of the star caused by the orbit of the planets. The accuracy of the spectrograph is unprecedented, since it can detect the confines of the solar system a "speeding" equivalent of a person walking.
Fleet of telescopes
It is this method which enabled Michel Mayor to identify the first Exoplanet in 1995. Most of the following specimens were also identified as well. Researchers do however not expect to find an exoTerre a few years, for this category of "lightweight" implies new detection technologies. Europeans including hope to launch this decade project Darwin, a flotilla of small telescopes as a very powerful interferometer.
In the meantime, the current methods of observation can still create surprises. "For a dozen years, we discovered that the diversity of the stellar systems is much larger than we thought." "Our solar system is more completely unique model", explains Michel Mayor. Whether life exists elsewhere in the universe, the debate is that start. Because even if astronomers are many exoTerres, biologists warn that the probability of seeing life appear remains tiny.