| Discovery of the planetary system as "populated" |
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 Astronomers, using the HARPS instrument leader of the ESO, have discovered a planetary system containing at least five planets orbiting the star HD 10180, a Sun-like star. The researchers also very promising signs indicating that two other planets must be present, one of which is the planet less massive discovered so far. If this happens, the system would be similar to our Solar System in terms of number planets (seven planets compared to the eight planets of the Solar System). In addition, the team also found evidence that the distances between the planets to their stars follow a regular pattern, as can also be seen in our Solar System. "We have found what the system is probably with the most planets discovered so far," said Christophe Lovis, the first author of the article describing this result. "This remarkable discovery also highlights the fact that we are now entering a new era of exoplanet research: the study of planetary systems and more complex than just the individual planets. The study of planetary movements of this new system reveals complex gravitational interactions between planets and gives us information on the evolution of this system over the long term. " The team of astronomers used the HARPS spectrograph installed on the 3.6 meter telescope at ESO La Silla in Chile to study for six years the Sun-like star, HD 10180, located 127 light years the Earth in the southern constellation of Hydrous (the Sea Serpent). The HARPS instrument, which measures the stability and accuracy are unparalleled, is the best planet hunter at the world Thanks to the 190 individual measurements of HARPS, the astronomers have detected a tiny moving back and forth from the star due to the gravitational attraction complex of five or more planets. The five strongest signals correspond to planets of mass similar to Neptune - between 13 and 25 Earth masses - in orbit around the star with periods ranging from 6 to 600 days. The distances between the planets from their stars range from 0.06 to 1.4 times the Earth-Sun distance. 'We also have good reasons to believe that two other planets are present, "said Christophe Lovis. One of them should be a planet like Saturn (with a minimum mass of 65 Earth masses) rotating around the star in 2200 days. The other should be the less massive planet ever discovered with a mass about 1.4 times that of Earth. It is very close to its star, only 2% of the Earth-Sun distance. A year on this planet would last only 1.8 day terrestrial. This newly discovered planetary system around HD 10180 is unique for several reasons. First, with at least five planets like Neptune spread over a distance corresponding to the orbit of March, the internal region of this system is more populous than our Solar System and there are much more massive planets. In addition, this system probably did not planet gas giant Jupiter-type. And again, all the planets seem to have a nearly circular orbit. Using this new discovery as well as data from other planetary systems, astronomers have found an equivalent to the Titius-Bode that exists in our Solar System: the distance between the planets to their stars seem to follow a regular pattern. "This could be a signature of the formation process of planetary systems," says Michel Mayor which is also part of this team. By studying these systems, the astronomers have discovered another important result: there is a relationship between the mass of a planetary system, and the mass and chemical content of its star. All systems were very massive planets found around massive stars and metal-rich while the four systems with smaller masses have been found around stars of lower mass and metal-poor. These properties confirm the theoretical models in force. |
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