The New York herald., 1922-02-26
FIRST PHOTOS TAKEN
OF FAR AWAY STARS
Harvard Observatory Puts It's
100000 Plates, Work of
Generation, to New Use.
TO MEASURE DISTANCES
Spectrum Method Adopted in
Determining Calculations
for Needed Data.

Special Dispatch TO THE New YoHK HERALD
CAMBRIDGE. Mass. Feb. 25.-Hundreds
of stars are having their distance from
the earth measured for the first time at
the Harvard College Observatory. The
university has more than 5000 plates,
photographs of star spectra, covering
the collection OF a generation. and these
are to be put to new use in determining
the distances of the stars. Work al
ready has started.
Many of the vast number OF stars
whose distances are still unknown are
the bright. comparatively near by south
ern stars, because nearly all the opser-
vatories where stellar distances are
measured are located in the Northern
Hemisphere. The Harvard astronomers
are therefore concentrating much of
their attention upon photographs of
southern stars taken at the Harvard sta
tion at Arequipa, Peru.
The new methods OF measuring the
distance of star by a study of its
spectrum are based upon discoveries by
a number OF astronomers. A remark
able contribution to tho subject has been
made by DR.. Neigh Mad Saba, an East
Indian. who is assistant professor OF
physics In the University OF Calcutta
Until recently the only available
method for measuring star distances has
been the parallax method. which con-
sists OF triangllation. using tho diam
eter of the earths orbit as a base line.
In other words. observations Of a star
arc made at intervals of about six
months.
To Seek Distant stars.
During this period Of six months the
observer Is carried by the motion of the
earth to a point some 100000 miles
from that OF his first observation, and.
using this distance as base line, he
can work out the distance. Of the nearer
stars.
Almost all the stars, however, are so
vastly remote from the earth that even
with a base line of 1ss,Oo0,000 miles
their distances cannot be triangulated.
1t is for these more distant stars that
the new methods are used. At the
Mount Wilson Observatory w. S. Adams
and his associates have succeeded in
developing a procedure depending on the
lines in the spectra OF stars as photo
graphed with large telescopes fitted with
powerful spectroscopes. 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 it's atmosphere. DR.. Bertil Lind
blad has provided another method, based
upon the examination OF the so-called
"cyanogen" bands In the spectra. These
new methods have been carefully
checked by the older ones.
Several years ago DR.. Harlow Shap-
! ley. then OF the Mount Wilson Observa-
tory and now director OF the Harvard
Observatory, found that very good esu-
mates of the distances OF stars could be
obtained from q study of the spectra as
| photographed directly with small tele-
scopes such as those generally used at
Harvard Then about year ago Saba,
the East Indian, established the most
certain fact that the spectrum or a star
shows not only what elements are pres
ent in II but also the degree of ionization
| OF the various elements present, and
thus by complicated physical reasoning
makes Il possible to estimate the tenn
perature and the size OF the star.
Must Determine Distribution.
His theory threw new light on the re-
! lation between the spectrum OF any star
and its absolute magnitude" or actual
brilliance. AS soon as the absolute mag
nitude OF any star is known this fact,
compared with the apparent magnitude
I
| its distance.
! Now that methods OF measuring star
distances from a study OF spectra have
| been worked out, standardized and
checked the next problem Is TO apply
these methods to those Thousands OF
stars whose distances are still unknown.
One OF the fundamental tasks OF astron-
/ omy is to determine how the stars are
distributed through space, and this can
never be known until the distances are
measured.
1t is this task OF applying the new
methods for which the Harvard collec-
| tion OF photographs Of stellar spectra
/ has been found to furnish excellent ma
terial. To give n single example: Pho
! tographs made at Cambridge thirty-five
/ years ago give the distance OF Alpha
CrsH Majoris. one of the pointers" in
! the Big Dipper, as about seventy-two
| light years. In other words. the light
now coming from that star began its
journey about 1850 and the light pho
| tographed on the Harvard plates in 1887