A resolved debris disk around the G2 V star HD 107146

We present resolved scattered-light images of the debris disk around HD 107146, a G2 star 28.5 pc from the Sun. This is the first debris disk to be resolved in scattered light around a solar-type star. We observed it with the Hubble Space Telescope/Advanced Camera for Surveys coronagraph, using a 1.8 occulting spot and the F606W (broad V) and F814W (broad I) filters. Within 2 from the star, the image is dominated by point-spread function subtraction residuals. Outside this limit, the disk looks featureless, except for a northeast-southwest brightness asymmetry that we attribute to forward scattering. The disk has scattered-light fractional luminosities of (L-sca/L-*)(F606W)=(6.8+/-0.8)x10(-5) and (L-sca/L-*)(F814W)=(10+/-1)x10(-5), and it is detected up to 6.5 away from the star. To map the surface density of the disk, we deproject it by, divide by 25degrees+/-5degrees the dust-scattering phase (g(F606W)=0.3+/-0.1, g(F814W)=0.2+/-0.1), and correct for the geometric dilution of starlight. Within the errors, the surface density has the same shape in each bandpass, and it appears to be a broad (85 AU) ring with most of the opacity concentrated at 130 AU. The ratio of the relative luminosity in F814W to that in F606W has the constant value of 1.3+/-0.3, with the error dominated by uncertainties in the value of g in each filter. An examination of far-infrared and submillimeter measurements suggests the presence of small grains. The colors and the derived values of g are consistent with the presence of dust particles smaller than the radiation pressure limit. Possible scenarios that may explain the shape of the surface density profile are the creation of a small planet or the scattering and circularization of a large one.