Originally posted by sonhouse
I just read a short piece in New Scientist about a binary black hole system 5 billion LY away that seems to be mutually orbiting each other and they give the numbers as 0.3 LY apart and taking 100 years to orbit one another. Given they are about the same mass, they would be mutually orbiting one another, can you calculate the orbital velocity as if one were ...[text shortened]... n? If not, how do you really calculate the mutual orbital velocity of two equal orbiting masses?
Without doing any calcuation, the assumption that the two eqaually massed black holes, of which one is stationary and fixed in space, must be false.
However, in order to keep the fomula simple I can agree to the assumptions, but then we have to make an error estimate accordingly.