Evening star., 1929-12-15
Continued From Third Page.l


exclamation of another curiosity of the
heavens. the globular clusters OF stars,
and found additional evidence OF a
yaster universe. This brilliant Work at
tracted the notice of astronomers all
over the world. With the death OF
Edward C. Pickering in 1919, the direc-
torship of the Harvard College OoServa-
tory became vacant. After Spenolng
months looking over the held the
Harvard Corporation offered this post
American astronomy-to this young
man at Mount Wilson who was then
busy exploring the outer fringes OF the
Milky Way.
Experiments in Early Days.
zone consideration which made the
opportunity very attractive to me. SAID
DR.. Snapley, twas Harvard'S collection
of stellar photographs Away back In
the early days of the daguerreotype, as
tronomers here began to experiment
with photography. In 1850 Prof. Bond
succeeded in photographing the bright
star Vega. The following year he made
the first photograph of the moon.
When Prof. Pickering became director,
in 1876, he continued these expert
ments. and, as photography increased
in sensitivity, applied it more and more
to astronomy. Here in Cambridge ne
set up clock-driven telescopes with
camera attachments, and made long
exposures of selected areas OF the SKY.
In 1889 he established station in Peru
torphotograph the southern stars.
"Thus for 40 years there has been
this continual Photographic patrol OF
the heavens, both north and south OF
the Equator. The result is an accumu-
lation of more than 300,0 900 negatives.
No resources for sounding and ana
living the universe could be more prom
ising OF rich returns than this vol
luminous picture gallery of the stars.
And so the quest begun at Princeton
and continued at Mount Wilson was
transferred to Harvard In 1921, When
DR.. Shapley became director OF the OBJ
servatory there. With this incompar-
able Photographic collection to draw
unon as a record Of the past, and with
eight Photographic telescopes working
eVery clear night making additional
comparison photographs, the most TAR
reaching survey ever projected has been
organized and is being carried forward.
-Four celestial objects, or kinds OF
objects, constitute the stellar universe
as we now know it, said DR.. Snapley,
land the survey here at Harvard is
organized into four researches, each
focused on one of these: First, the
Milky Way: second, the globular clus-
ters. which are outside the Milky Way;
third. the Magellanic Clouds, which are
more remote: fourth, the outside gall
axies. which are still farther distant
from our system.
10000 Plates to Be Made.
''The Milky Way survey alone will re-
Af nn0E0s
graphic plates now on hand and the
making Of at least 10000 new plates OF
long exposure. Three telescopes IN
Cambridge and two in South Africa are
in continuous use during clear nlghts
to get these photographs, and six as
tronomers and mathematicians are at
work analyzing, computing, reducing
and interpreting the results. An Incl
dental outcome will be the discovery
of hundreds of new stars. We may
even double the number OF known
variable stars, for we are picking the
Milky Way to pieces and examining II
mart bv part under the magnifylng
glass"
I asked DR.. Shapley to describe some
of these pieces into which ne mas
dissected our stellar system.
'WeIl, one is the star cloud in whlch
NE live f" he answered. More than hall
the stars YOU see with the naked eye
are In this local cloud. Inc clouu; al
turn, is composed of many open clusters
such as the Pleiades, which Is several
hundred stars travelling as grouP.
and of field stars which traVeI alohe'
our sun is field star. ..,
"Our local cloud seems TO De traVel-
ire at present through another clouo.
'The brightest star in our SKY, the ocg
star Sirius. is apparently member OF
on omen cluster which is not OF our
local system. This cluster is all around
,Is for in addition to SIRIUS In tne
southern sky it includes flve OF the Big
Dipper stars In the northern SKY auu I
MANY stars between. Curlously, Tie
two end stars of the Big Diper do not
helong to the cluster. They are moving
IN Southerly direction while the clus-
ter is moving northerly, and in a Few
hundred thousand years the Big Dlpper
will be distorted out Of its familiar
pattern" ,,. 2 mn
light years across. But 1t is only
small fraction Of the Milky way, loE
DIR. Shapley's latest researches indicate
a galactic diameter OF the order OF
2O0O 900 light years. When he frst an
noInced this dimension most astrono-
mers were doubtful. 1t was too vast
iump too sudden an expansion, from
the conception of few years ago: But
the evidence has continued to pile up,
and now there are very few who ques-
tion the validity Of Shapely's measure
rnent The center of the galaxy, as de-
termined recently, is in the constella"
ton SagittariuS.
DR.. Shapley's second research focuses
on the globular clusters. How are they
sienifcant?" I asked.
Help Measure Dimensions.
"They have proved wonderfully help
ful in measuring the dimensions OF our
galaxy" he answered 1T is largely be-
cause of evidence from the globulal
clusters that 1 set 100000 light years
as the minimum estimate for the galac-
tic diameter.
"The globular clusters are quite diff
ferent from the open clusters found If
the Milky Way, such as the Pleiadcs
and Hyades. They are larger and more
uniform, great globular swarms. There
are Just SO of them. When we charteo
their positions we found that while
none we're within the Milky Way they
were relatively near and In fact outline
the galactic boundaries. They are
evenly distributed, Al being on one side
of the galaxy and 46 on the other
MANY of these clusters are approaching
our system at high velocities. and 1t Is
my belief that they pass through al
intervals.
1T seems TO me that we have possibly
a key to the process by which our Milky
Way has been built up," continued Dr
Shapley. Every time one OF the glob'
ular clusters sweeps through our system
IL is subjected to the enormous gravita.
tional pull of the larger mass OF the