Veille ufologique américaine
Prof. relates extraterrestrial researchBy Brendan Dooley, Friday, May 14, 2010The search for habitable planets beyond our solar system has long been a subject of interest for astronomers and non-astronomers alike. But it was not until NASA launched the Kepler Mission in 2009 that there was enough data to begin seriously analyzing “super-Earths,” giant planets and Earth analogs, according to Dimitar Sasselov, a professor of astronomy at Harvard University who directs Harvard’s Origins of Life Initiative.Sasselov spoke to audience members in a colloquium Wednesday afternoon sponsored by the Department of Physics and Astronomy.Before astronomers could begin to look for and analyze Earth-like extrasolar objects, they needed to gather large quantities of accurate statistics and data, Sasselov said.“We were woefully behind in doing our homework to find if life is on other planets, and a key part of the Kepler Mission is trying to catch up,” Sasselov said.While previous missions examining extrasolar objects were only able to view giant planets, the Kepler Mission allows astronomers to view relatively small planets with masses much closer to that of the Earth, Sasselov said.The Kepler Mission uses the “transit method” to find information about the physical characteristics of a planet, Sasselov said.The transit method of detecting extrasolar planets uses photometry — the study of an object’s electromagnetic radiation — to study a planet’s movement around its parent star. Scientists can contrast the levels of brightness as the planet crosses in front of its parent star and ultimately determine the relative size of the planet to star, Sasselov said.The Kepler Mission can find transits more easily than previous telescopes because it has an extremely large field of view in comparison to other space telescopes — such as the Hubble Space Telescope — which dramatically increases the number of stars that Kepler can view and provides a far better chance of viewing transits, Sasselov said.“The mission is a telescope which is specially designed to discover planets like the Earth, and the way it does that is by having a very large field of view of very good optical quality,” he said.The Kepler Mission maintains a single field of view containing over 15 million stars in order to provide astronomers with “an uninterrupted field of view to maximize our chances of finding as many planets as we could,” according to Sasselov.The Kepler Mission was originally pitched to NASA with the goal of gaining information through statistical analysis, Sasselov said.“You start with the radius, the mass and the mean density [of planets,] and then you try to extract as much information as you can from it,” Sasselov said.The accuracy of the statistics has surpassed the expectations of most astronomers and has enabled them to engage in astroseismology, a way of studying the interior structures of planets and stars, he said.“We didn’t anticipate that the results would be good enough to do astroseismology — the accuracy here is just unprecedented,” Sasselov said.Sasselov, who has been a member of the Kepler team for 10 years, said the mission has provided unprecedented levels of data that have enabled astronomers to continually refine their understanding of Earth-like objects outside of our solar system.“[Kepler] keeps sending us data, and the longer the data stream has become, the more interesting things we have been able to find,” Sasselov said.He added that once enough information is gathered through astroseismology, astronomers can begin to determine the geochemistry of distant super-Earths, or planets that are larger than Earth but smaller than the gas giants Saturn and Jupiter. The goal is to see if they have any “biomarkers,” or signs that may indicate conditions to support Earth-like life, such as active surface crust.“Right now I’m getting a lot of parameters from Kepler for what I want to do next, which is to find the geochemistry of those super-Earths,” Sasselov said.Sasselov acknowledged, however, that there are limitations to what the Kepler Mission can accomplish.“Kepler can drive us all the way to the point that we can start thinking about biomarkers, but I don’t think we will be able to go much farther than that,” Sasselov said.
le télescope spatial Corot découvre sept exo-planètes14 juin 2010 Les équipes scientifiques du télescope spatial Corot annoncent la découverte de sept nouvelles exoplanètes. Des géantes gazeuses d'une grande diversité de tailles et d'orbites qui viennent s'ajouter aux près de 450 exo-planètes découvertes depuis le milieu des années 1990.Parmi les 7 nouveaux trophées du palmarès Corot, Corot-15b, «est un objet particulièrement intéressant, explique Pascal Bordé de l'Institut d'Astrophysique de Paris. Il est à mi-chemin entre planète et étoile. C’est ce qu’on appelle une naine brune. Sa densité moyenne est énorme, 7 fois celle de l’acier.» Corot-10b présente une orbite particulièrement allongée autour de son étoile. La température pourrait donc y varier entre 250°C et 600°C en quelques jours. Corot-11b, tourne autour d’une étoile en rotation étonnamment rapide sur elle-même : 40h contre 26 jours pour notre Soleil. Corot-8b est la plus petite de la série. Elle mesure 0,7 fois la taille de Saturne et pèse 0,7 fois sa masse. Sa structure interne est comparable à celles des planètes géantes de glace, comme Neptune et Uranus dans le système solaire. Si Corot est à l'origine de ces découvertes, elles sont toutefois validées et précisées à l'aide de télescopes terrestres, le Very Large Telescope de l'Observatoire européen austral, au Chili et des spectrographes HARPS (installé sur le 3,60 m de l'ESO au Chili) et SOPHIE (installé sur le télescope de l'Observatoire de Haute Provence) qui mesurent la masse et le rayon des planètes. A ce jour, 450 exoplanètes ont été découvertes grâce aux télescopes du monde entier. En mars dernier, le Cnes avait annoncé la découverte d'un Jupiter à 1500 années lumière de la Terre.Le télescope spatial, piloté par le CNES depuis Toulouse, a encore de beaux jours devant lui puisque sa mission vient d’être prolongée de 3 ans. Lire ici et ici les articles publiés lors du lancement de Corot.
Au fait, qui peut me dire comment on fait pour mettre un lien sans mettre le lien ?
-Parmi ces 16, la plus petite fait 1,9 fois la taille de la Terre, il s'agit de Gliese 581e
Citer-Parmi ces 16, la plus petite fait 1,9 fois la taille de la Terre, il s'agit de Gliese 581eRecord en passe d'être battu par la nouvelle découverte - L’autre devrait être la planète la moins massive jamais découverte avec une masse d’environ 1,4 fois celle de la Terre. - si son existence et les calculs sont confirmés bien sûr.Car il s'agit bien de masse et non pas de taille. Ces objets sont bien trop minuscules et éloignés pour qu'on puisse estimer leur taille.
