Und dann aber die wirklich wichtige Information bei Cosmology.berkeley.edu:
But I digress. What if the Sun did become a black hole for some reason? The main effect is that it would get very dark and very cold around here. The Earth and the other planets would not get sucked into the black hole; they would keep on orbiting in exactly the same paths they follow right now. Why? Because the horizon of this black hole would be very small — only about 3 kilometers — and as we observed above, as long as you stay well outside the horizon, a black hole's gravity is no stronger than that of any other object of the same mass.