Evening star., 1925-09-07
Other Worlds
BY james StokIey.


they believed, were subordinate to It,.
Then came Nicolaus Copernicus who
showed that the earth was merely
one of system of planets revolving
around the sun. A hundred years
ago the great English astronomer.
Sir William HerscheL demonstrated
that the sun. together with all the
other stars that we see in the heay-
ems, formed vast system roughly the
shape of grindstone. And now, as
men, DIR. Edwin p. Hubble of Mount
Wilson Observatory has shown that
the universe of stars is but one of
many such uniyerses. thousands OF
which dot the sky, and may be seen
as far rs our great modern telescopes
can reach.
Recently DIR. Hubble told the mem
bers Of the National Academy of
Sciences of his work. Then he eX-
planned how. with the great 100-inch
rejecting telescope, the largest in
the world, he had made many photo
graphs of two of the nearest of these
universes. or spiral nebulse, as the
astronomers call them. Previously
they had often been photographed
with smaller telescopes, and always
appeared as continuous areas OF
light, much the same as the Milky
Way appears 10 the unaided eye.
Hordes of Stars.
But just as the Milky Way is seen
with even a small telescope to con-
sist of hordes of stars, so did DIR.
bubbles photographs reveal the
stars of which these spiral nebulae
consist. He told how. applying a
method successfully used on the
nearer Giobular star clusters by his
former collegue at Mount Wilson,
DR.. Harlow Shapely, now director of
the Harvard College Observatory, he
had found their distance
This method was possible because
the photogra phs showed a number
OF stars which undergo a periodic
variation of light, and from the time
that ii takes the star TO complete
one Of these cycles of varying bright
ness. the astronomer can calculate
their actual brilliancy. Knowing how
bright they actually are, and how
bright they appear on the photo
graphs. their distance may be
measured, because light diminishes
creases. In such a way, DR.. Hubble
found the distance of these two spi-
rails was each about a million light
years-a million times six trillion
miles; the distance that light, NOV
ing with speed sufficient to encircle
the earth seven times in A second,
can travel in a million years
But this did not satify some of the
astronomers. This method they
said, in effect, has only been tested
on much shorter distances We do
not know whether or not they would
act the same when so far away" II
is TO answer this objection that DIR.
Hubble is now working, and as l sat
in his office one morning he showed
me how, by two quite independent
methods, he has arrived at similar
distances. He finds that the stars
in the spirals seem TO behave the
same as our system would if II were
removed so far from US. There have
been observed in the andromeda
nebula, one of the two that he has
studied. SO "novate." or rev stars.
These occasionally appear in our own
system when star, formerly very
faint. flares up for a while, and then
gradually returns TO its former magni-
tude. If we assume that the aver
ge brightness of those In the spirals
is similar to those in the Milky Way,
their apparent faintness may be ex-
planned If they are at much greater
distance, and the distance is about
a million light years.
Photograpfing the Stars
Important and epoch making as this
work is, il is merely a part Of the
work going on at the Mount Wilson
Observatory. which boasts larger
staff than any similar institution. The
100-inch telescope, for example. is
used in great variety of ways. as
is the 60-inch telescope, the third
largest in the world. One of the chief
uses is in photographing the spectra
of stars, from which, by DR.. Adams
method, their distance may be found
but these spectra also tell, 10 those
who can read the message, many
other facts rs to the stars motion
and composition. Photographs made
with these two instruments are also
used by DR.. Adrian Van Maanen in
measuring stellar distances, or paraI-
lakes, by their displacements due IN
the motion of the earth in it's orbit.
and revealed when photographs made
six months apart are compared
From the start. when the observa-
tory was founded by DIR. George
many years. until poor health forced
him to resign and assume the posi-
tion of honorary director, which he
now holds, the sun has been one of
the principal objects of study In
deed, until a few years ago. it was
officially called the Mount Wilson
Solar Observatory of the Carnegie
Institution of Washington" but now
the word solar" in the title has been
dropped. Erected solely for solar
study are the two lower telescopes,
one IS feet and the other 150 feet
high, which may be seen surmount-
ing Mount Wilson from the city of
Pasadena and also from more distant
points. Each of these consists of a
steel tower. with a dome at the top.
In each dome Is an arrangement of
mirrors which collect the sunlight
and reflect it into a lens. forming an
image of the solar disc at the base
With them direct photographs may
be made, or else the sun may be pho
tographed by the light of one of the
elements that il contains, such as
hydrogen or calcium. This is accom-
plished with the "spectroheiiograph,
an ingenious instrument of DR.. Hale s
invention. But this is not sufficient
and under each tower is a well. 80
feet deep Tor the snlaiier tower ana
rs feet for the larger. At the bot
tom of each we'll is a diffraction
grating, which, like a prism, breaks
up the sunlight into a spectrum. This
is reflected hack to the base of the
tower, where photographs are made
showing the dark spectral lines which
mean so much to the astronomer.
Every clear day and with the
southern California climate there are
usually about 500 of them annually,
the sun is photographed in every pos
sible way. This work has continued
for many years, and already has led
to the discovery of numebr of i'm
portant facts concerning the source