I present detailed analysis of the near infrared spectrum of HD 3651B , a faint , co-moving wide companion to the nearby planet-hosting star HD 3651 .
These data confirm the companion as a brown dwarf with spectral type T8 , consistent with the analysis of Luhman et al .
Application of the semi-empirical technique of Burgasser , Burrows & Kirkpatrick indicates that HD 3651B has T _ { eff } = 790 \pm 30 K and \log { g } = 5.0 \pm 0.3 for a metallicity of [ M/H ] = 0.12 \pm 0.04 , consistent with a mass M = 0.033 \pm 0.013 M _ { \sun } and an age of 0.7–4.7 Gyr .
The surface gravity , mass and age estimates of this source are all highly sensitive to the assumed metallicity ; however , a supersolar metallicity is deduced by direct comparison of spectral models to the observed absolute fluxes .
The age of HD 3651B is somewhat better constrained than that of the primary , with estimates for the latter ranging over \sim 2 Gyr to > 12 Gyr .
As a widely orbiting massive object to a known planetary system that could potentially harbor terrestrial planets in its habitable zone , HD 3651B may play the role of Nemesis in this system .