The Astrology of Space - Matrix Software

The Astrology of Space
The Stellar Associations
Very loose galactic clusters are called Stellar
Associations and were discovered in the late 1940s.
These associations are almost spherical in shape and
yet have very low spatial density. The differential
revolution about the galactic center should have
elongated these groups of stars in a few hundred
million years. This is due to the fact that the portion of
the galactic disc nearer the center of the galaxy
revolves more rapidly than the outer edge of the disk,
in a pseudo-Keplerian motion. The lack of elongation
noted in associations indicates that they must have
been recently formed and are expanding at velocities
of the order of 5 to 10 km/sec. If so, their ages cannot
exceed a few millions or tens of millions of years.
Young associations are of spherical shape (circular in
outline) and older associations suffer distinct
elongation as would be expected from the effect of
galactic differential rotation, the spinning galactic disk.
The official definition of stellar associations in the
words of their founder V.A. Ambartsumian: "O-
Associations are stellar systems where the partial
density of '0' and 'B2' stars [spectral class] is larger
than the average field density of these stars in such a
way that this difference cannot be explained by
chance fluctuations; moreover, '0' or 'BO' stars are
present."
The radii of these associations range up to 200
parsecs, far exceeding a typical open cluster or even
that of the mighty globular clusters. It has been found
that many associations outline the three major spiral
arms of our galaxy. An association may contain 100
stars and it is estimated that ten million stellar
associations have passed through their evolutionary
cycle during the lifetime of our galaxy, each ending in
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