  The "holy grail" in planet hunting is the detection of an Earth-analog: a
planet with similar mass as the Earth and an orbit inside the habitable zone.
If we can find such an Earth-analog around one of the stars in the immediate
solar neighborhood, we could potentially even study it in such great detail to
address the question of its potential habitability. Several groups have focused
their planet detection efforts on the nearest stars. Our team is currently
performing an intensive observing campaign on the alpha Centauri system using
the Hercules spectrograph at the 1-m McLellan telescope at Mt John University
Observatory (MJUO) in New Zealand. The goal of our project is to obtain such a
large number of radial velocity measurements with sufficiently high temporal
sampling to become sensitive to signals of Earth-mass planets in the habitable
zones of the two stars in this binary system. Over the past years, we have
collected more than 45,000 spectra for both stars combined. These data are
currently processed by an advanced version of our radial velocity reduction
pipeline, which eliminates the effect of spectral cross-contamination. Here we
present simulations of the expected detection sensitivity to low-mass planets
in the habitable zone by the Hercules program for various noise levels. We also
discuss our expected sensitivity to the purported Earth-mass planet in an
3.24-d orbit announced by Dumusque et al.~(2012).
