Another recycled thread.
Sten Odenwald's Astronomy Cafe (aka The Space Scientist, aka Ask the Astronomer) is the number 8 link on the BA's Top Ten Picks, and I enjoy reading the Space Scientist pages, but I've found some errors.
The Space Scientist has a list of errors webpage, but it is incomplete. In fact, the last paragraph says that he'd corrected Where is the center of mass of the Pluto-Charon system located? to say that the Pluto/Charon barycenter was 700 miles beneath the surface of Pluto. Pluto's radius is less than 700 miles, and he meant 700 kilometers, of course, as it does say in the answer, but even that is wrong.
The answer has the following equation:
19,700 x (0.000123/(0.0024+0.000123) = 19,300
The left hand side is actually equal to 960, more or less, not 19,300, which would put the barycenter 200 km below the surface of Pluto, instead of 700 km.
Still, the mass of Charon appears to be three times as great as that, and the barycenter is actually 1200km above the surface of Pluto.