The Washington herald., 1911-07-09

the heavens is limited by the brilliance
OF the full moon. which. therefore, be-
comes the principal object for the anna
teur astronomer to study. By Thursday
evening the moon will be rising so late
that It may not occupy the attention OF
the observation party at the Observa-
tory, for these little gatherings last only
from until 10 o'clock. But last week
the moon was a wonderfully interesting
subject through the powerful lenses of
the big telescope, and Prof. Peters sci
entifc discussion of some of it's prin-
cipal features was received with rapt at
tention by the star gazers.
Before you can look at the moon with
any intelligent eve there are certain SIM
pie facts you should know. The moon
is the satellite of the earth. 1t is gen.
orally believed among scientists that it
was once part of the earth, but broke
away during the earliest stages of the
earth's formation and went drifting off
into space. The momentum 1t received
from the spinning earth started the
moon in its course eastward around our
globe. and the attraction of the earth
was sufficient to keep its satellite from
d
The orbit of the moon around the earth
is elliptical and its mean distance Is
about 244,0OO miles. The moon makes a
circuit OF the earth in twenty-eight days,
and during that time turns only once OH
It's. axis, which accounts for the fact
that the same face of the moon is al
ways turned toward the earth's surface.
A moments thought will make this clear
to any one.
The surface OF the moon is very noun
famous, and under the powerful telescopes
these mountain ranges are brought plain
ly into view. The mountains are OBJ
viously OF volcanic origin, some of the
great craters being more than 100 miles
across. The dark area in the upper right
hand portion of the moons surface is a
great, smooth depression that is sup
posed to be the bed of what once was a
sea. As there no longer is any atmos-
phere on the moon. there can be no water
or snow or life of any kind. The moon
is about One-sixth the size of the earth
These simple facts about the moon,
facts which all of us knew when we were
children. but which so many OF US have
forgotten completely, are all that one
of the luna surface brought to the eye
by even a small telescope
JupIter's Many Satellites.
Jupiter is such a brilliant object these
days that a few remarks about this larg-
est of the planets should be of interest
AS seen through the Pinch telescope at
the observatory, the surface of Jupiter
becomes a fairly large, notified disk,
streaked with bands of clouds. Jupiter
has eight moons, four of which are WIS.,
ible through the glass at this time.
Jupiter is about S9OCO miles in diameter.
or eleven times the size of our earth, and
is about 49OOOO,OCO miles from the sun.
1t revolves around the sun in aborI
twelve years. Jupiter is so large that al
though 1t is many millions of years older
than the eaEth, 1t has not passed the
period of the great rains from which the
oceans are formed and the crust of the
surface cooled. Its surface therefore is
always hidden from view by the great
masses of clouds envelopinS its entire
surface.
There are two interesting shooting-star
showers which occur during July, be-
sides many faint cnes. Any one of the
dark, moonless evenings near the 18th
of the month the careful observer will