The detection of exoplanets using any method is prone to confusion due to the
intrinsic variability of the host star. We investigate the effect of cool
starspots on the detectability of the exoplanets around solar-like stars using
the radial velocity method. For investigating this activity-caused "jitter" we
calculate synthetic spectra using radiative transfer, known stellar atomic and
molecular lines, different surface spot configurations, and an added planetary
signal. Here, the methods are described in detail, tested and compared to
previously published studies. The methods are also applied to investigate the
activity jitter in old and young solar-like stars, and over a solar-like
activity cycles. We find that the mean full jitter amplitude obtained from the
spot surfaces mimicking the solar activity varies during the cycle
approximately between 1 m/s and 9 m/s. With a realistic observing frequency a
Neptune mass planet on a one year orbit can be reliably recovered. On the other
hand, the recovery of an Earth mass planet on a similar orbit is not feasible
with high significance. The methods developed in this study have a great
potential for doing statistical studies of planet detectability, and also for
investigating the effect of stellar activity on recovered planetary parameters.Comment: Accepted to MNRA
