From the Milky Way as a whole we pass to the vast clouds, swarms, and
clusters of stars of which it is made up. It may be, as some
astronomers hold, that most of the galactic stars are much smaller
than the sun, so that their faintness is not due entirely to the
effect of distance. Still, their intrinsic brilliance attests their
solar character, and considering their remoteness, which has been
estimated at not less than ten thousand to twenty thousand light-years
(a light-year is equal to nearly six thousand thousand million miles)
their actual masses cannot be extremely small. The minutest of them
are entitled to be regarded as real suns, and they vary enormously in
magnitude. The effects of their attractions upon one another can only
be inferred from their clustering, because their relative movements
are not apparent on account of the brevity of the observations that we
can make. But imagine a being for whom a million years would be but as
a flitting moment; to him the Milky Way would appear in a state of
ceaseless agitation -- swirling with ``a fury of whirlpool motion.''
The cloud-like aspect of large parts of the Galaxy must always have
attracted attention, even from naked-eye observers, but the true
star-clouds were first satisfactorily represented in Barnard's
photographs.
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