No. 19: Jan-Feb 1982
According to the physical laws governing orbital motion in a central force field, like that of our sun, distant objects should rotate more slowly than those closer to the central mass. Thus, the outer planets of the solar system swing around the sun more slowly than the earth and the other inner planets.
Astronomers always expected that the stars rotating around the massive hubs of the galaxies would obey these laws in a like manner. No such luck! Doppler measurements of galaxy rotations made by Vera C. Rubin and her colleagues, at the Carnegie Institution, indicate that most stars out near the galactic rims rotate just as fast or faster than those closer to the hub. Astronomers suppose that this anomalous rotation may be due to halos of undetected burntout stars and/or gas fringing the galaxies. Such halos would dis-tort the inverse-square-law field, permitting the observed anomalous rotation.
(Anonymous; "Fast-Spinning Galaxies," Science Digest, 89:18, November 1981.)
Comment. No one has yet discovered these hypothetical halos of mass. The universe seems to be full of "missing mass." An unpopular alternative would be the admission that Newton's Law of Gravitation does not hold on the galactic scale.