The Trouvelot astronomical drawings manualTrouvelot, E. L. (Etienne Leopold)
Science
The Trouvelot astronomical drawings manual
Trouvelot, E. L. (Etienne Leopold)
Astronomy -- Pictorial works
Among the 1,034 objects which are now classified as clusters more or
less resolvable, 565 have been absolutely resolved into stars, and 469
have been only partly resolved, but are considered as belonging to this
class of objects. In Sir J. Herschel's catalogue there are 102 clusters
which are Considered as being globular; among them 30 have been
positively resolved into stars.
The agglomeration of thousands of stars into a globular cluster cannot
be conceived, of course, to be simply the result of chance. This
globular form seems clearly to indicate the existence of some bond of
union, some general attractive force acting between the different
members of these systems, which keeps them together, and condenses them
towards the centre. Herschel regards the loose, irregular clusters as
systems in a less advanced stage of condensation, but gradually
concentrating by their mutual attraction into the globular form.
Although the stars of some globular clusters appear very close together,
they are not necessarily so, and may be separated by great intervals of
space. It has been shown that the clusters are agglomeration of suns,
and that our Sun itself is a member of a cluster composed of several
hundreds of suns, although, from our point of observation, these do not
seem very close together. So far as known, the nearest star to us is a
Centauri, but its distance from the Earth equals 221,000 times the
distance of the Sun from our globe, a distance which cannot be traversed
by light in less than three years and five months. It seems very
probable that if the suns composing the globular clusters appear so near
together, it is because, in the first place, they are at immense
distances from us, and in the second, because they appear nearly in a
line with other suns, which are at a still greater distance from us, and
on which they accordingly are nearly projected. If one should imagine
himself placed at the centre of the cluster in Hercules, for instance,
the stars, which from our Earth seems to be so closely grouped, would
then quite likely appear very loosely scattered around him in the sky,
and would resemble the fixed stars as seen from our terrestrial station.
Public-domain text, read in full here on John Shaqi.
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