In the early 1900's, it was discovered, from proper motion studies of the, brighter stars, that the stars, in general, are moving in two preferred directions toward the apparent vertices. These points are situated in Lepus, at R.A 90° and declination, -15°, and in Pavo at R.A. 285°, declination -64°.

About 60% of the stars belong to Stream I, moving toward the Lepus vertex, and 40% belong to Stream II, moving toward the Pavo vertex at a velocoity about half that of Stream I. Not all stars share in the streaming, however; type A stars are very prone to do so, and type F and later classes in the spectral sequence show the same tendency, though less strongly. Most type stars are not members of either stream, but seem to be practically stationary. They are moving with the Sun. (see Local System).

If the apparent streaming is corrected for solar motion, the streams are found to be moving toward diametrically opposite points in the plane of the galaxy -- the true vertices at R.A. 95°, Declination +12° in Orion , and R.A. 275°, declination -12° in Scutum. Star streaming has been explained as the result of small deviations from circular orbits.

Copyright (c) 1997-99 Michael Erlewine