Evening star. [volume] (Washington, D.C.) 1854-1972, 1931-02-09
new DEVICE BARES
SOLAR PHENOMENA
SpeCtroheIiosCopeS Built by
Carnegie Institute Aid
Photographers.
What's new on the sun?

What's new on the sun?
The Carnegie Institution of WASH
ington is developing spot news" serv-
ice for daily events there.
Six OBSERVATION-DISCLOSURES, the institution
announces. have been built at the Mount
Wilson Observatory and furnished to
observatories in England, Italy, Syria,
New Zealand and Samoa. At the same
time other observatories, including one
in China are securing similar inStru-
mentS tested by the Carnegie as
tronumers. Each spectrohelioscope con-
stitutes a small but efficient solar OBJ
servatory.
This instrument is an invention of
DR.. George E. Hale, honorary director
of the Mount Wilson Observatory, by
which it is possible to observe the solar
prominences. geySers of flaming gas which
sometimes extend from the surface of
the sun for thousands of miles into
space. These have been found to be
the forerunners of magnetic storms on
earth, auroTas and other geophySical
disturbances which are expected to be-
come of increasing Importance as sci
ence learns more about them, espe-
ccially as explaining such things as va
riations in radio receptivity.
Aids Observations.
The spectrohelioscope allows obser-
vations of the suns face to be taken by
the light of single ray of the spectrum,
the light of all other rays being cut off.
Ordinarily the solar prominences can
be seen only during a total eclipse.
Otherwise the brilliance of the suns
radiation destroys the details of its sur
face. In order to have predictive value
it is necessary to know about the yaria-
tionS all the time.
With the spectrohelioscope the only
requirement is a clear day. With nu-
merous observing stations scattered all
over the world the astronomers win es-
cape the vicisSitudes of local weather
and nearly constant observation may
lead to a better knowledge of the exact
relationship between terrestrial and solar
phenomena.
Meanwhile the Carnegie astronomers
with their delicate instruments are
reaching across the 100000 miles be-.
tween the earth and the sun to deter
mine still finer details of the phenomena
of its surface. This work involves max
ing fine determinations of temperature
at different places by means of a ther-
omocouple. Radiation from one spot
on the sun falls through pin-hole
aperture on junction of two fine wires
of different elements through which is
flowing an electric current which Is re-
corded by a galvanometef to which the
wires are attached The variation in
this current caused by the heating of
the junction is a fine measure of the
temperature at the source of radiation.
Heat on Sun Varies.
They found that the suns surface is
not equally hot at all places. At the
center of the disk the rate of radiation
was found to be 16 per cent greater
than that for the disk as whole, from
which they calculated a temperature of
approximately 5495 Y. Considerably
cooler than this We the reversing
layer" which gave temperature of APP
proximately 1910. The surface of the
sun seen with the naked eye is the
photosphere, but above this is a COM
paratively thin red envelope which can
ordinarily be differentiated only during
an eclipse. This is made up of a COM
paratively cool gas which has been split
into two layers. The basic one, lying
next to the photosphere, is the reversing
layer.
The sun spots, dark patches on the
face of the sun, some of which are
greater than the earth in diameter,
were found to be considerably cooler
than the surrounding photoSphere. The
results indicate approximately 1910 r.
for the center Of such spot, the tenn
perature falling of steadily as the pin
point aperture Is moved inward from
the light philosophers.
Sun Speeds Up.
The sun, like the earth, is turning on
its axis, at the rate Of about a mile
second. The rate of this rotation varies
from time to time Carnegie measure
ments show that the equatorial velocity,
which apparently has been decreasing
for several years, seems to have reached
minimum and is showing a slight
tendency to increase.
Sun spots occur in groups. The clas-
giflcation of all sunspot groups and
measurement of the intensity of their
magnetic fields is being continued daily.
During the past year 313 direct photo
graphs of the sun were made. The
Carnegie astronomers also are making
fine measurements of the ultraviolet
and infra-red radiations Of the sun and
the variations in these from day to day.
At the same time other astronomers
are trying to determine, by analysis of
the spectra. what elements are present
in the sun spots. Some indications
have been found Of the presence of
molecular hydrogen, and this is being
further investigated Daily observa-
tons are made on the number and ac-
tivity of the sun spots, which appear to
increase and decrease in cycles.