Stéphane Udry
Obs. Genève, Univ. Genève (Sauverny, Suisse)
Salle des séminaires Évry Schatzman, Institut d'Astrophysique de Paris
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| « Extrasolar planets: an emerging population of Neptunes and super-Earths » |
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Stéphane Udry |
| The statistical results gathered on exoplanet properties over the past decade provide important observational constraints for planet- formation models. I f most of the known planets are gas giants, since a couple of years, high-precision radial-velocity measurements are unveiling a population of light planets with masses in the Neptune or super-Earth mass range. The emergence of this population is mainly due to the HARPS search for low-mass extrasolar planets targeting a few hundreds of G and K dwarfs of the solar neighbourhood, and which has been ongoing since 5 years on the ESO 3.6-m telescope. The published low-mass planetary systems demonstrate the sub-m/s long-term stability reached by HARPS. A preliminary scanning of our sample reveals over 40 candidates having minimum masses below 30 Earth masses, and orbital periods below 50 days. These numbers are preliminary since the existence of these objects has to be confirmed by subsequent observations. However, they indicate that about 30% of solar-type stars may have such close-in, low-mass planets. In this seminar, I will briefly recall the known observational properties of giant planets and compare them with the emerging properties of the new population of Neptune-mass and super-Earth planets, in the light of results from the state-of-the-art planet-formation models. I will also discuss the limitations of the radial-velocity method and the associated optimistic perspectives for the future detection of Earth- like planets with radial-velocities alone or in complement to space photometry. |
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vendredi 27 février 2009 - 11:00 Salle des séminaires Évry Schatzman, Institut d'Astrophysique de Paris |
| Page web du séminaire / Seminar's webpage |