Until we have a CCD survey of the
whole sky, which is not going to happen anytime soon, we really can't be confident that we have a good sample of
nearby galaxies, says Bothun.
Re 51 Tom P — watched the video; and I agree that the sun does wobble around the center of mass of the solar system; the center of mass itself is not tending to wobble around the sun because conservation of momentum applies to the solar system as a
whole (except of course for the forces applied to it by
nearby stars, the rest of the
galaxy, etc, but those are not varying so fast and so the center of mass should generally be moving along rather smoothly on the same timescale as planetary motions).