The stability of the orbits of Earth-mass planets in the habitable zone of 47 Ursae Majoris

We have investigated whether Earth-mass planets could survive in the habitable zone (HZ) of the 47 Ursae Majoris system. Mixed-variable symplectic numerical integration has been used to investigate the orbits of putative Earth-mass planets. Whereas the 47 UMa system as previously known, with just one giant planet, could have Earth-mass planets that remain confined to the HZ for a fairly wide range of initial obital parameters, the second (outer) giant now known to be present has reduced the range significantly. There are however confined orbits particularly if either the present eccentricity of the outer giant is close to zero, or the giant masses are close to the minimum values. We have also shown that the eccentricity of the outer giant's orbit is unlikely to exceed about 0.15 at minimum giant mass and 0.13 at 1.5 times this minimum.