The daily variation of the solar photocenter over some 11 years is derived
from the Mount Wilson data reprocessed by Ulrich et al. 2010 to closely match
the surface distribution of solar irradiance. The standard deviations of
astrometric jitter are 0.52 μAU and 0.39 μAU in the equatorial and the
axial dimensions, respectively. The overall dispersion is strongly correlated
with the solar cycle, reaching 0.91μAU at the maximum activity in 2000.
The largest short-term deviations from the running average (up to 2.6 μAU)
occur when a group of large spots happen to lie on one side with respect to the
center of the disk. The amplitude spectrum of the photocenter variations never
exceeds 0.033 μAU for the range of periods 0.6--1.4 yr, corresponding to
the orbital periods of planets in the habitable zone. Astrometric detection of
Earth-like planets around stars as quiet as the Sun is not affected by star
spot noise, but the prospects for more active stars may be limited to giant
planets.Comment: Accepted in Ap
