Precision radial velocities from Keck/HIRES reveal a Saturn-mass planet orbiting the nearby M4V star HIP 57050 .
The planet has a minimum mass of M \sin i \sim 0.3 M _ { J } , an orbital period of 41.4 days , and an orbital eccentricity of 0.31 .
V-band photometry reveals a clear stellar rotation signature of the host star with a period of 98 days , well separated from the period of the radial velocity variations and reinforcing a Keplerian origin for the observed velocity variations .
The orbital period of this planet corresponds to an orbit in the habitable zone of HIP 57050 , with an expected planetary temperature of \sim 230 K. The star has a metallicity of [ Fe/H ] = 0.32 \pm 0.06 dex , of order twice solar and among the highest metallicity stars in the immediate solar neighborhood .
This newly discovered planet provides further support that the well-known planet-metallicity correlation for F , G , and K stars also extends down into the M-dwarf regime .
The a priori geometric probability for transits of this planet is only about 1 % .
However , the expected eclipse depth is \sim 7 \% , considerably larger than that yet observed for any transiting planet .
Though long on the odds , such a transit is worth pursuing as it would allow for high quality studies of the atmosphere via transmission spectroscopy with HST .
At the expected planetary effective temperature , the atmosphere may contain water clouds .