Аннотация: The spot coverages S for 2846 solar-type stars with effective temperatures from 5700 K to
5800 K and gravities from 4.4 to 4.5 have been measured. An analysis based on the MAST catalog, which
presents photometricmeasurements obtained with the Kepler Space Telescope duringQ9 is presented. The
existence of two groups of solar-type stars, with S values between 0.001 and 0.007 and withS > 0.007, is
inferred. The second group (active stars) contains 279 stars (about 10 % of the total number of stars
analyzed). The mean S parameter for the entire sample is 0.004, comparable to the mean spot coverage
of the Sun. In general, the dependence of S on the rotation period for solar-type stars has characteristics
similar to those found earlier for stars with exoplanets. For the vast majority of the stars in the sample, the
activity is constant, and independent of age. The activity of the small number of active stars withS > 0.007
decreaseswith age. The age variations of the chromospheric activity index R_HK are compared to variations
of the spot coverage S. The relations analyzed have common characteristic features. It is likely that both
the spot activity level and the chromospheric activity level abruptly decrease for stars older than 4 billion yrs.
DOI: 10.1134/S1063772917050067