Extra-solar planets transiting their host stars allow numerous key studies, giving access to radii, masses, and densities, atmospheres in absorption and emission, obliquity measurements... This incited numerous ground and space searches for transiting planets. Among them, the space telescope Kepler has provided hundreds of planetary candidates. Radial velocity measurements are mandatory to establish the planetary nature of most of them and to measure their mass. In synergy with the radial velocity follow-up programs of Kepler planetary candidates we are conducting with the SOPHIE spectrograph at the 1.9-m telescope of Observatoire de Haute-Provence, we started complementary programs with the HARPS-N spectrograph, recently installed at the Telescopio Nazionale Galileo and taking advantage of the higher efficiency of that 3.6-m telescope. It already allowed the detection and characterization of the planets KOI-200b and KOI-889b, the two first ones with HARPS-N. Both planets are located at the frontier between regimes where tides can explain circularization and where tidal effects are negligible. Whereas KOI-200b is Darwin unstable, KOI-889b is one of the few known planetary systems to be Darwin stable.

The two optical lattice clocks we have built at LNE-SYRTE are in agreement at a level better than the uncertainty on the realization of the second. Less than 10 years after the initial proposal, this is the first time this type of clocks beat this limit. We have also checked the reproducibility of these clocks versus the 3 independent Primary Frequency Standards (PFS) of the laboratory, we found an excellent agreement, now solely limited by the performances of the PFS, both in stability and in accuracy. The stakes are high, not only in terms of improved performances for time metrology (timekeeping, time-stamping, synchronization, positioning systems), but also in terms of fundamental science: optical clocks have become so accurate that they could very soon unravel the smallest perturbations of the gravitational potential or even detect drifts of the fundamental constants, thus prodiving new tools to explore hypothetical limits of the standard model. References: "Experimental realization of an optical second with strontium lattice clocks", R. Le Targat et al., Nature Communications, 07/2013 Article: http://www.nature.com/ncomms/2013/130709/ncomms3109/full/ncomms3109.html ArXiv: http://arxiv.org/abs/1301.6046 Press link: http://www.insu.cnrs.fr/node/4450?utm_source=DNI&utm_medium=Newsletters