The larger movements, however, ascribed to
some of the fainter associated stars are far from harmonizing with
this preconceived notion of what they ought to be.
On the contrary, so far as they are known at present, they force upon
our minds the idea that the cluster may be undergoing some slow
process of disintegration. M. Wolf's impression of incipient
centrifugal tendencies among its components certainly derives some
confirmation from Dr. Elkin's chart. Divergent movements are the most
strongly marked; and the region round Alcyone suggests, at the first
glance, rather a very confused area of radiation for a flight of
meteors than the central seat of attraction of a revolving throng of
suns.
There are many signs, however, that adjacent stars in the cluster do
not pursue independent courses. "Community of drift" is visible in
many distinct sets; while there is as yet no perceptible evidence,
from orbital motion, of association into subordinate systems. The
three eighth-magnitude stars, for instance, arranged in a small
isosceles triangle near Alcyone, do not, as might have been expected
_a priori_, constitute a real ternary group. They are all apparently
traveling directly away from the large star close by them, in straight
lines which may, of course, be the projections of closed curves; but
their rates of travel are so different as to involve certain
progressive separation.
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