Evening star. [volume] (Washington, D.C.) 1854-1972, 1930-09-14
BY THOMAS R. HENRY.

Far out in space the tiny planet, Eros,
is moving rapidly toward the earth.
Astronomers at the Naval Observatory
here already are making preliminary
observations of this moving point Of
light In the heavens, which, during its
present visit, is expected to furnish q
new "yardstick of the solar system. +"
It viii be photographed again and
again by observatories scattered over
the earth In q world cooperative pro-
gram sponsored by the international
Astronomical Union, which Is expected
to shed new light on zone Of the most
fundamental problems In astronmy.
VIII Enter Orbit Of Mars.
The little planet-it Is not much more
than a big boulder wkirling around in
space-will come during January to
within 100000 miles of the earth.
measurable celestial object, except for
the moon, In many years. Eros will
swing well within the orbit Of Mars,
but will stay outside the earths orbit.
Eros Is only one Of q thousand odd Of
the earth's baby sister planets, little
masses of rock moving in orbits around
the sun. 1t Is about Is miles in di-
ameter and, astronomers believe, ir-
regular In figure, because of its queer
habit Of disappearing at certain stages
of its progress. 1t now is q star of
times less brilliant than can easily be
seen with the naked eye-and when 1t
comes closest to the earth probably can
be seen with field glasses.
It is Of extreme importance to as
tronon1erS for two reasons. First, 1t
comes very close to the earth. Second,
1t is so small that It can be considered
as a mathematical point having no
mass, breadth or thickness to upset cal
culations.
Sun Is Inadequate "Yardstick."
If astronomers knew the exact dis
lance Of any object In the solar sys-
TEN they could calculate with equal
exactness the distance Of any other OBJ
Ject. But, 1t Is explained at the Naval
Observatory, they do not The present
yardstick, used for measuring plane
tary distances, is the space between the
earth and the sun. Astronomers can
determine exactly that an object in the
heavens is three times as far away as
the sun or one-half as far away. This
can, after a fashion, be reduced to terms
Of miles, but with a rather high degree
OF error, because they do not know
how many miles away the sun Is.
The present calculated distance oil
the sun Is 92,870,000 miles. The &C.
cepted figures In the United States wa
calculated by Prof. Simon Newcombe
formerly Of the Naval Observatory, US
ing about 100000 observations extend
ing over approximately $50 years.
Astronomers in other countries have
worked out the problem with about the
same results. And this figure, the
astronomers say, is correct within some
such trifiing error as 100000 miles
They want to get rid of this error-in-
significant when the extent of the
heavens is considered but Of vital i'm
portance when 1t occurs in the yard
stick of space.
Astronomers Find Sun Too Big.
Actually, the sun-one of the stars
and treated as such by astronomers
Is not exactly where it should be, &C
cording to Newcomers calculations
Its mean longitude is OF about one
and-a-half seconds Of arc The sun Il
so big that it makes precise astrononi-
cal calculations difdcult. It's radius