Take two stars of equal masses (say 10^32 kg), separate them
by a chosen distance (d=10^13 m), give them appropriate
initial positions (say r1=0.5*d*i, r2=-r1), and initial velocities
(say v1=1.826*10^4*i, v2=-v1). This makes a system in
which each star traces a circle of r=d/2 about the C.M. The
speed of the C.M. (in the absolute newtonian frame) is zero.
The same should be true for a proton and antiproton. To have
them circle about the common C.M. (and keep the angular
momentum = 1 h_bar) the distance between the particles should
be about 5.76*10^-15 m (58 F) while |v|=1.1*10^6 m/s. Was a
proton-antiproton "binary star" ever observed experimentally?
Should it be called a heavy neutron or a hydrogen "atom"?
Ludwik Kowalski