  Magnetic activity and surface flows at different scales pertub radial
velocity measurements. This affects the detectability of low-mass exoplanets.
In these flows, the effect of supergranulation is not as well characterized as
the other flows, and we wish to estimate its effect on the detection of
Earth-like planets in the habitable zone of Sun-like stars. We produced time
series of radial velocities due to oscillations, granulation, and
supergranulation, and estimated the detection limit for a G2 star and a period
of 300 days. We also studied in detail the behavior of the power when the
signal of a 1 Mearth planet was superposed on the signal from the stellar
flows. We find that the detection rate does not reach 100% except for the
supergranulation level we assume, which is still optimistic, and for an
excellent sampling. We conclude that with current knowledge, it is a very
challenging task to find Earth twins around Sun-like stars with our current
capabilities.
