Stars of the southern skiesOrr, M. A. (Mary Acworth)
Science
Stars of the southern skies
Orr, M. A. (Mary Acworth)
Southern sky (Astronomy); Stars
Both Clouds consist of gaseous nebulae and star-clusters on a
background of vague nebulosity and crowds of almost indistinguishable
stars. But the white nebulae shun the Clouds, just as they shun the
Milky Way.
An immense number of variable stars have been discovered in the Clouds
of Magellan, of the same type as those in globular clusters. Miss
Leavitt of Harvard Observatory catalogued from photographs no less
than 969 in the Lesser Cloud and 800 in the Greater. In the latter
the greatest number of variables was found in a stream of faint stars
which connects a group of star-clusters with the Looped Nebula, and
others occur locally in certain parts of the Cloud, but few are in
its northern region or in parts where many of the brighter stars
congregate. All the variables are very faint, the usual minimum in both
Clouds being about fourteenth magnitude, and the maximum seldom more
than one magnitude brighter. A few in the Lesser Cloud have been found
with periods unusually long for this “cluster type” of variables,
amounting to 32, 66, and even 127 days. These longer periods seem to
belong to somewhat brighter stars, but they are quite as exact as the
usual period of a few days or a single day.
XVII
THE MILKY WAY
Like a great river returning into itself, the Galaxy encircles the
starry heavens, and those who know only its northern course have no
idea of its brilliance and wonderful complexity in its brightest part.
Its light is soft, milky, and almost uniform, between Cygnus and
Sirius, but when it enters Argo it becomes extremely broad, and spreads
out like a river on a flat marshy plain, in many twisting channels with
spaces between. Where Canopus shines on the bank there is a narrow
winding ford right across its whole breadth, as if a path had been made
by the crossing of a star.
After this it suddenly becomes extremely narrow, but so bright that all
the light which was shining in the broad channel seems to be condensed
in this narrow bed. In the brightest, richest part the Great Nebula of
Argo is easily distinguished by the naked eye. Contrasting with this
and other bright condensations are black gaps, the largest and blackest
of which is the well-known Coal-Sack near the Southern Cross.
[Illustration: THE MILKY WAY IN SCORPIO, LUPUS, AND ARA
Photographed at Hanover, Cape Colony,
by Bailey and Schultz]
Public-domain text, read in full here on John Shaqi.
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