A Text-Book of AstronomyComstock, George C. (George Cary)
Science
A Text-Book of Astronomy
Comstock, George C. (George Cary)
Astronomy
These two bodies are known as the Magellanic clouds, and individually
bear the names of Major and Minor Nubecula. According to Sir John
Herschel, "the Nubecula Major, like the Minor, consists partly of large
tracts and ill-defined patches of irresolvable nebula, and of nebulosity
in every stage of resolution up to perfectly resolved stars like the
Milky Way, as also of regular and irregular nebulæ ... of globular
clusters in every stage of resolvability, and of clustering groups
sufficiently insulated and condensed to come under the designation of
clusters of stars." Its outlines are vague and somewhat uncertain, but
surely include an area of more than 40 square degrees--i. e., as much as
the bowl of the Big Dipper--and within this area Herschel counted
several hundred nebulæ and clusters "which far exceeds anything that is
to be met with in any other region of the heavens." Although its
excessive complexity of detail baffled Herschel's attempts at artistic
delineation, it has yielded to the modern photographic processes, which
show the Nubecula Major to be an enormous spiral nebula made up of
subordinate stars, nebulæ, and clusters, as is the Milky Way.
Compared with the Andromeda nebula, its greater angular extent suggests
a smaller distance, although for the present all efforts at determining
the parallax of either seem hopeless. But the spiral form which is
common to both suggests that the Milky Way itself may be a gigantic
spiral nebula near whose center lies the sun, a humble member of a great
cluster of stars which is roughly globular in shape, but flattened at
the poles of the galaxy and completely encircled by its coils. However
plausible such a view may appear, it is for the present, at least, pure
hypothesis, although vigorously advocated by Easton, who bases his
argument upon the appearance of the galaxy itself.
Public-domain text, read in full here on John Shaqi.
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