Evening star., 1935-12-07
: STARS, MEN AND ATOMS
Notebook of Science Progress in Field,
Laboratory and Study.
BY THOMAS r. HENRY.

The Milky Way system with its 50,-
900 900, 900 stars is unit of local su-
pergalaxy-one of thousands of such
supergalaxieS in the vastness of known
space.
This supergalaXy is about million
light years in diameter-that IS, 1t would
take light moving at 10000 miles a
second a million years to go from one
end to the other. Five members of this
great aggregation of galaxies are known,
all within less than million light years
of the earth. There may be dozens of
others hidden from the eye of the tele-
scope behind obScuring cosmic dust
clouds in the region of the Milky Way.
At least one other member Of this
family-the great nebulae in the con-
stellation of Andromeda-is approx
mately equal in size and similar in con-
Stitution to the enormous aggregation
of stars of which the sun is close to the
average. This neighbor is only 100000
light years away. It is the only one
of the external galaxieS visible to the
naked eye It's total mass is at least 10
billion times that of the sun. 1t is
moving at a very rapid rate in the
direction of the Milky Way system.
Much smaller aggregations of stars
which constitute dynamic systems dis
tinct from the Milky Way galaxy, but
which are members of the same super
galaxy, are the greater and lesser Ma
gellanic clouds, visible in the Southern
Hemisphere. There are two other
smaller galaxies, of which little is known.
The concept of the local, Supergalaxy
is advanced by DR.. Forrest Ray Moulton,
former professor of astronomy at the
University of Chicago and associate of
the Carnegie Institution of washington,
in his recently published volume, Con-
slider the Heavens"
In this supergalaxy, he points out,
the nearest and most easily studied OBJ
jectS are the Magellanic clouds. Both
clusters constitute galactic systems of
the second rank, small in comparison
either with the Milky Way galaxy or
the great nebulae in Andromeda. The
largest of these clouds is only about one
sixth the size Of our own galaxy-10, 600
light years in diameter compared to
10000. Yet 1t contains at least SOC, 600
per-giant and giant stars which can
easily be discerned with telescopes and
probably 100 times as many more which
are too small to be seen as distinct
objects. 1t is about $4,000 light years
from the outermoSt limits of the Milky
Way system.
The lesser Magellanic cloud is about
10000 light years away and is only about
5000 light years in diameter. It's internal
composition, however, is approximately
the same as the other and both contain
all the classes of stars which have been
catalogued in the Milky Way system.
Both might be considered as poor rela-
tions of the Milky Way and Andromeda
systems.
The Andromeda nebulae, as described
by DR.. Moulton, is quite q different OBJ
ject. 1t was first observed and cata-
logued by the Arabs long before the In
vention of the telescope. For centuries
nobody suspected its real nature. 1t was
considered as a vast gas cloud, the raw
material from which stars later would
be constituted. 1t was not until 1917
that, with the aid of improved telescopes,
astronomers began to discern separate
stars in the cloud and its nature was
established.
Determination Of the fact that the
Andromeda nebulae was actually q
galaxy, comparable in size to the Milky
Way system itself, opened up for astron-
omers the greatest of all fields of dis
covery. Within a few years the known
magnitude of creation was expanded mil
lions Of times as more powerful tele-