The HARPS survey for southern extra-solar planets

Abstract

In this letter we present the discovery of a very light planetary companion to the star µ Ara (HD160691). The planet orbits its host once every 9.5 days, and induces a sinusoidal radial velocity signal with a semi-amplitude of 4.1 m s−1, the smallest Doppler amplitude detected so far. These values imply a mass of m2 sin i = 14 M⊕ (Earth-masses). This detection represents the discovery of a planet with amass slightly smaller than that ofUranus, the smallest “ice giant” in our Solar System. Whether this planet can be considered an ice giant or a super-earth planet is discussed in the context of the core-accretion and migration models. Key