Evening star., 1952-04-25
Half of the Heavens
Declared Invisible
Noted British Astronomer
Tells of Radio Sturs'
By Thomos R. Henry

Half the heavens may be invisible.
There may be as many radio stars"
as visible stars in the Milky Way galaxy.
the great conglomeration of more than
100 billion celestial objects of which the
solar system Is a minute part.
This is the conclusion Of DR.. j. A.
Ratcliffe of Cambridge University, Eng
land. one Of the worlds foremost experts
on the new radio astronomy. The con-
clusion reported in Nature. organ Of
the British Association for the Advance
ment of Science, is almost necessary to
account for the enormous amount Of
radiation in the radio range which
reaches the earth from outer space.
Thus far only about so of these So
called radio stars" have been located.
None of them yet has been identified
with visible object
Two Windows in Blanket"
Any object as hot as visible star can
be expected to send out radiation cover
ing nearly the entire spectrum from
extremely short X-rays through ultra
violet visible, infra-red light to the
longest radio waves. The earth's at
mosphere is an effective blanket against
most of this radiation. There are.
however, two windows. One admits
waves of visible light ranging from red
to violet. The other admits short radio
waves, none more than a few meters
long.
Only within the past few years has 1t
been realized that these short radio
waves were associated with specific OBJ
jects. The nature of these, DR.. Ratcliffe
points out, remains highly debatable.
Nearest of the radio-wave emitters Is
the sun. From it's surface comes a con-
slant background radiation of this sort.
The radio sun" is somewhat larger
than the visible sun, presumably be-
cause it includes the corona, the circle
of pearl-gray light around the solar
disc which is visible only during
total eclipses. Some of this solar
radiation theoretically requires tenn
perature of more than million degrees.
1t long since had been established that
the temperature Of the light-emitting
surface of the sun is only about 5000
degrees. The new evidence is consid-
cred conclusive that the temperature OF
the vacuum-thin corona, extending per-
haps a million miles into space. il
around million Fahrenheit. This find-
ing is one of the major accomplishments
Of the new astronomy.
The suns radiation Is enormously in
creased at times, usually associated with
intense SunSpot activity. If every other
star could be assumed as sending out
this invisible radiation at the same rate
as the disturbed sun 1t would account
for between a hundredth and q thou
sandth Of that observed.
Disc Believed Cooler. .-..
With these considerations something
different from stars Of the suns pattern
must be assumed. No particular increase
in radio-wave emission is observed from
some of the known hottest stars in Gre
alton which are not too far away from
the sun, as stellar distances 60. It must
be conjectured then, DR.. Ratcliffe holds.
that a radio star is an object with q
very much cooler disc than the sun
probably so cool that it is invisible ex-
cept in it's immediate neighborhood-
and q vastly hotter corona.
A few billion such stars would 20 far
toward explaining the tremendous radi-
alton received from the galaxy.
The fact that no object Of any sig
nificance has been observed in those
parts Of the sky from which comes the
most intense radiation is not in itself
proof that the objects are invisible. DR..
Ratcliffe says. 1t is impossible to PIN
point radio-wave sources. '
Some of the most intense radiation.
he says, comes from directions in which
lie other galaxies comparable in size to
the Milky Way galaxy. It is almost cer-
tain that some Of the radiation Is from
these outer "universeS."