From frozen Super Earth to habitable Earth via microlensing.


J.P. Beaulieu (1), P. Fouqué (2), V. Batista (1), A. Cassan (1), C. Coutures (1), D. Kubas (1), J.B. Marquette


(1) Institut d’Astrophysique de Paris, UMR 7095, CNRS UPMC, 98bis Boulevard Arago, 75014 PARIS, (2) Observatoire Midi-Pyrénées, Laboratoire d’Astrophysique (UMR 5572), Université Paul Sabatier - Toulouse 3, 14, avenue Edouard Belin, 31400 TOULOUSE


In the last fifteen years, astronomers have found over 415 exoplanets including some in systems that resemble our very own solar system. These discoveries have already challenged and revolu-tionized our theories of planet formation and dynamical evolution. Several different methods have been used to discover exoplanets, including radial velocity, stellar transits, direct imaging, pulsar timing, astrometry, and gravitational microlensing which is based on Einstein’s theory of general relativity. So far 10 exoplanets have been published with this method. While this number is relatively modest compared with that discovered by the radial velocity method, microlensing probes a part of the parameter space (host separation vs. planet mass) not acces-sible in the medium term to other methods. The mass distribution of microlensing exoplanets has already revealed that cold super-Earths (at or beyond the “snow line” and with a mass of around 5 to 15 Earth mass appear to be common (Beaulieu et al., 2006, Gould et al., 2006, Sumi et al. 2010) . We detected a scale 1/2 model of our solar system (Gaudi et al., 2008), several hot Nep-tunes/Super Earth, shown that our detection efficiencies extends to 1 Earth mass planets (Ba-tista et al., 2009). We have made the first meas-urement of the frequency of ice and gas giants beyond the snow line, and have shown that this is about 7 times higher than closer-in systems probed by the Doppler method (Gould et al. 2010). This comparison provides strong evi-dence that most giant planets do not migrate very far (Gould et al. 2010). Microlensing is currently capable of detecting cool planets of super-Earth mass from the ground (and on favourable circum-stances down to 1 Earth), with a network of wide-field telescopes strategically located around the world, could routinely detect planets with mass as low as the Earth. I will stress the importance of high angular resolution using adaptive optics on 8m class telescopes during microlensing events in order to nail down the physical parameters of the star and planet systems to 10 %.

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