Le 21 mai 2015
De 10h30 à 12h00
Amphithéâtre de la Grande Coupole
Michel MAYOR
Observatoire Astronomique de l’Université de Genève
During the last 20 years, an important fraction of the 2000 exoplanets presently known have been discovered by Doppler spectroscopy. Today, progress of astronomical instrumentation, permit the detection of planets with masses comparable to the Earth.
I will report on the results of an 11-year survey carried out at la Silla Observatory with the HARPS spectrograph to detect and characterize planets in the super-Earth and Neptune mass regime. The size of our sample and the precision achieved with HARPS have led to the detection of a sufficiently large number of low-mass planets to study the statistical properties of their orbital elements, the correlation of the host star metallicity with the planet masses, as well as the occurence rate of planetary systems around solar-type stars.
What are the expected development of Doppler spectroscopy ? Searching for rocky planets in the habitable zone of solar-type stars is certainly a goal of high priority. The challenge is to detect radial velocity amplitude of some 0.1 m/s over periods of one year. Present spectrographs have a sufficient sensitivity. The spectrograph ESPRESSO in construction to be implemented in a couple of years on the 8-m telescopes at Paranal Observatory is an example of these new instruments. The major difficulty comes from the intrinsic variability of the velocity resulting from the stellar magnetic activity. Optimized strategy of observation seem indicate that the detection of such planets is feasible.
The synergy between ground based Doppler spectroscopy and space missions (CHEOPS,TESS and PLATO) offers exceptional possibilities.