The HARPS search for southern extra-solar planets XI. Super-Earths (5 & 8 M_Earth) in a 3-planet system

摘要

This Letter reports on the detection of two super-Earth planets in the Gl581system, already known to harbour a hot Neptune. One of the planets has a massof 5 M_Earth and resides at the ``warm'' edge of the habitable zone of thestar. It is thus the known exoplanet which most resembles our own Earth. Theother planet has a 7.7 M_Earth mass and orbits at 0.25 AU from the star, closeto the ``cold'' edge of the habitable zone. These two new light planets aroundan M3 dwarf further confirm the formerly tentative statistical trend for i)many more very low-mass planets being found around M dwarfs than aroundsolar-type stars and ii) low-mass planets outnumbering Jovian planets around Mdwarfs.