Richmond daily register. (Richmond, Madison County, Ky.) 1917-1978, 1922-04-28
DISTANCES OF
STARS MEASURED
New Method Being Employed by
Astronomers at Harvard
College Observatory.
BASED ON STUDY OF SPECTRUM
Vast Collection of Photographs Nov
Being Used and Exact Figures
No Longer Depend on
Old System.

Cambridge, MaSS.-1ne distance
from the earth of hundreds Of stars
are now being measured for the first
time at Harvard College Observatory
by recently developed methods based
upon a study of the spectrum. 1t las
been found that the huge collection
Of photographs of star spectra, as
sembled at Harvard during the p"st
generation and numbering over $50.
600 plates, can be put Ito new use
in determining the distance of sta.s
and the work OF measurement is So-
ing ahead rapidly.
Many of the vast number of stars
whose distances are still unknown are
the bright, comparatively nearb.
southern stars, because nearly all the
where stellar distances
are measured are located in the north
ern hemisphere. The Harvard astron-
omerS are therefore concentrating
much Of their attention upon photo
graphs of southern stars at the Har-
ward station at Arequipa, Peru.
new Metnoo.
The new methods of measuring The
distance of a star by aLstudy of its
spectrum are based upon4diSGpyerie
by number OF Astronomers A re-
markable contribution ito the, subject
has been made by Dir. Neigh Mad Saba,
an East Indian, who is assistant pro
fessor of physics in the University of
Calcutta.
Until recently the only available
method for measuring star distances
has been the parallaX method, which
consists of triangulation, Using the
diameter of the earth's orbit as base
line. In other words, observations of
star are made at intervals of about
six months. During this period of six
months the observer is carried by the
motion Of the earth to a point some
1856 million miles from that of his first
observation, and using this distance
as a base line he can work out the
distances of the nearer stars.
Almost all the stars, however, are
so vastly remote from the earth that
even with a base line of 1856 million
miles their distances cannot be TRAN
gulated.
1t is for these more distant stars
the Mount Wilson observatory, W. s.
Adams and his associates have sue
ceeded in developing a procedure de-
pending on the lines in the spectra of
stars as photographed with large tele
scopes fitted out with powerful spec
troscopes. The lines are due to the
absorption Of light from the stars
surface by the clouds of iron, nickel,
calcium and other elements that form
its atmosphere Dir. Bertil Lindblad
has provided another method, based
upon the examination of the so-called
"cyanogen" bands in the spectra.
These new methods have been care
fully checked by the older ones.
The Next Problem.
Now that methods of measuring
star distances from a study of spec
ira have been worked out standard |
lied and checked, the next problem is
to apply these methods to those thou |
sands of stars whose distances are
still unknown. One of the funda-
mental tasks of astronomy is to de- |
termine how the stars are distributed |
through space, and this can never he |
known until the distances are meas
ured.
1t is this task of applying the new !
for which the Harvard col |
lection of photographs of stellar spec |
ira has been found to furnish eX-
,ellent material To give a single eX- i
ample, photographs made, at Cam
bridge thifty-five years ago. give the
distance Of Alpha Ursae -MaiQriS: one |
Of the pointers" in the big dipper,
rs about seventy-twosigh years, mi
other words the light now coming in
from that star began its journey about
1880, and the light photographed on
the Harvard plates in 1857 started in
1873.