• DOI:10.1051/0004-6361:20054084
• Corpus ID: 119078261

The HARPS search for southern extra-solar planets - V. A 14 Earth-masses planet orbiting HD 4308

@article{Udry2006TheHS,
  title={The HARPS search for southern extra-solar planets - V. A 14 Earth-masses planet orbiting HD 4308},
  author={St{\'e}phane Udry and Michel Mayor and W. Benz and J L Bertaux and François Bouchy and Christophe Lovis and Christoph Mordasini and Francesco A. Pepe and Didier Queloz and J. P. Sivan},
  journal={Astronomy and Astrophysics},
  year={2006},
  volume={447},
  pages={361-367}
}

• S. Udry, M. Mayor, +7 authors J. Sivan
• Published 12 October 2005
• Physics, Geology
• Astronomy and Astrophysics

We present here the discovery and characterisation of a very light planet around HD4308. The planet orbits its star in 15.56 days. The circular radial-velocity variation presents a tiny semi-amplitude of 4.1 m/s that corresponds to a planetary minimum mass m2sin(i)=14.1 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 m/s, 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, HD4308 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 models.