The HARPS search for southern extra-solar planets


We present here the discovery and characterisation of a very light planet around HD 4308. The planet orbits its star in 15.56 days. The circular radial-velocity variation presents a tiny semi-amplitude of 4.1 ms−1 that corresponds to a planetary minimum mass m2 sin i= 14.1 M⊕ (Earth masses). The planet was unveiled by high-precision radial-velocity measurements obtained with the HARPS spectrograph on the ESO 3.6-m telescope. The radial-velocity residuals around the Keplerian solution are 1.3 ms−1, demonstrating the very high quality of the HARPS measurements. Activity and bisector indicators exclude any significant perturbations of stellar intrinsic origin, which supports the planetary interpretation. Contrary to most planet-host stars, HD 4308 has a marked sub-solar metallicity ([Fe/H]=−0.31), raising the possibility that very light planet occurrence might show a different coupling with the parent star’s metallicity than do giant gaseous extra-solar planets. Together with Neptune-mass planets close to their parent stars, the new planet occupies a position in the mass-separation parameter space that is constraining for planet-formation and evolution theories. The question of whether they can be considered as residuals of evaporated gaseous giant planets, ice giants, or super-earth planets is discussed in the context of the latest core-accretion

Extracted Key Phrases

10 Figures and Tables

Citations per Year

386 Citations

Semantic Scholar estimates that this publication has 386 citations based on the available data.

See our FAQ for additional information.

Cite this paper

@inproceedings{Mayor2005TheHS, title={The HARPS search for southern extra-solar planets}, author={Michel Mayor and Xavier Bonfils and Thierry Forveille and Xavier Delfosse and St{\'e}phane Udry and J . L . Bertaux and Herv{\'e} Beust and François Bouchy and Christophe Lovis and Francesco Pepe and Nuno Miguel Carvalho Santos}, year={2005} }