Evening star., 1950-05-26
u. of Va. Astronomers
Mop Suns Neiohbors
100000 Stellar Objects
Photographed in Survey
BY Thomos r. Henry

CHARLOTTESVILLE, Va, May 36.-
Mapping the suns NEUTRALITY-SUSPICIOUS. Of
the major Jobs Of modern aStronomy-1
nearing completion here.
University Of Virginia astronomers
have photographed the spectra OF the
stars within q tiny patch Of celestial
space. a radius Of about 800 trillion miles
with the solar system approximately In
the center. Their plates now include
about 25o.o0o stellar objects reaching
down TO stars Of about the 18th magni-
tude. many times fainter than can hs
seen with the naked eye.
Only about 20 per cent Of the stars
Photographed can be seen without the
aid Of telescope. Actually the stellar
objects themselves are not photographed.
but their spectra, the more prominent
wave lengths of light which they emit
This makes possible the determination
OF something Of their structure and ab-
solute brightness and gives clues to those
whose distance can be determined With
considerable exactness by angular mea-
surements from the earth.
Notable Findings.
Many years will be required for the
study Of these spectra. but already there
have been some notable findings First,
considerable number Of the stars In
this nelghborhood appear to be double
two stars each revolving around the other
and all turning around q common center,
This is the case with the nearest Of all
stars to the sun. Alpha Centauri In the
southern heavens. 1t may be characters
Tic OF the entire universe. according to
DR.. Harold Alden. director Of the obsery-
atory.
Another surprising finding is the num-
Der OF small. red cool stars in this neigh
oorhood. The majority of them range
from 30th to hundredth as bright as
the sun. Their surface temperatures
presumably range around 1000 degrees
c.. compared to more than 5000 for the
sun.
Presumably there are thousands of
much Fainter stars in the suns neigh
borhood. some Of them far too faint 10
be detected by any telescope. Their
existence can be surmised only when
they form parts of double or triple sys-
TENS by their gravitational effects on the
motions Of visible stars.
Rotation Speed Studied.
BY means of these spectra photo
graphs the Virginia astronomers are
studying the speed Of rotation of stars
Presumably all Of them are turning
around an axis like the sun itself, but
this can be observed indirectly only for
very few. There are star spots. just
ike sun spots. They presumably are
great whirlpools in the stellar atmos-
pheres. The temperature Of sunspot
areas Is slightly less than that OF the
surrounding surface. This Is presumed
"a ali aPw
not be observed directly but when q very
slight dimunition Of temperature Is OBJ
served occurring regularly 1t is assumed
10 De Que to the passage Of one Of them
across the face Of the camera with its
attached photo-electric cell. The pc
riod OF such drops in temperature can be
taken as the period Of the stars rotation.
Many more observations must be made
before definite conclusions can be reach
ed, DR.. Alden says. but 1t appears as II
stars were rotating at all sorts Of speeds.
Certainly none Of them are standing
still. q.
Phenomenon Of Flareups.
The Virginia ASTRONOMERS also report
the curious phenomenon OF star fare
ups. 1t Is well known that the heat out
put OF the sun varies from day to day.
The variations. however. are extremely
minute and barely within the limits of
measurement. Even 50 they are postu-
lated to be major factor in the earth's
weather. Occasionally q So-called nova"
appears in the heavens. A star suddenly
becomes hundred to thousand times
brighter than normal
Many Of the stars in the suns neigh
borhood, the Virginia astronomers have
found. seem to fall somewhere between
the sun and nova. They blaze up to
several fold their normal brightness in
two or three minutes. and then subside
to normal again. II this ever happened
on the sun. 1t undoubtedly would wipe
out life on earth.