Daily Kennebec journal., 1902-12-09
THE DECEMBER SKIES.
The ConsteIIations-The Planets-The
Moon Phases.

nOur OF nine o CLOCK Oh Dec. 10, We find
near the horizon the two dog-stars.
Sirius and Procyon. The latter is
nearly due east, and is somewhat
higher up than the former, which. even
at it's present low altitude, gives evil
dence of its surprising brightness. Both
these stars are among our near neigh
bors in space, and both are attended
by faint companions. visible only With
the largest telescope. ..,.-4.
Above Sirius is Orion, with the
bright red star Betelgeuse on the left.
and the still more brilliant Rigel lower
down on the right. Gemini, which lies
above Procyon, has also. pair of
bright stars. The upper one is named
Castor. and the lower Pollux. Still
higher up are Auriga (above GeminD
and Taurus (above Orion) bearing the
bright stars Capella and Aldebaran. 80.
The long line of faint stars which
begins at Rigel and can be traced
westward, then southwark, and then
back towards the southeast, forms the
Eridanus. Its one bright
star, Achernar, which nearly equals
.Rigel. can be seen at this season low
on the southern horizon from places
south Of latitude 80 degrees. The large
constellation of Cetus. the Whale, oc-
cupies great part of the southern
sky. The monsters head is marked
by an irregular pentagon of small
stars, which is now on the meridian,
about halfway up to the zenith. The
brightest. star in the constellation, Beta
Ceti. lies nearly forty degrees to the
westward, and is the only conspicuous
one in the southwestern sky. at.
Aries is nearly on the meridian above
Cetus, and Perseus is directly over
head. Observable minima of Algol will
occur on the 1sth at II p. NJ, on the
18th at p. NJ, and on the 18th at p.
M. AndrOmeda and Pegasus are the
most conspicuous consultations to the
west of the zenith. Cygnus is still visi-
BILE in the northwest and Lyra is low
on the horizon. Ursa Minor and
Draco are below the pole. Ursa Major
coming up to the east of it, and Cassio-
pela and Cepheus high on the west.
The principle used by astronomers
to determine the distance of stars Is
exactly that Of the rangefinder en-
ployed by modern gunners. Bearings
are taken on the distant target from
two points as far apart as is practical
BILE. Knowing the distance between
these points, the distance of the target
can be calculated from the difference
OF its bearing at the two points. When
we come to apply this method to the
stars. we find that the whole diameter
of the earth is far too short base
line. Fortunately, We have longer
one available, the diameter of the
earth's orbit. BY taking observations
of star at properly chosen dates six
months apart, we have a base 1S6000.-
900 miles long, and can proceed with
some chance of success. -. +.t,...
The next question is: How can we
measure the bearing of the star with
sufficient accuracy? The best way is to
choose. some small stars near the one
TO be investigated. and use them as
points of reference. Such small stars are
usually so far away that their change of
bearing may be neglected, while the
nearer star appears to be Slightly dis
placed with reference to them. Occasion
ally the faint star chosen is no farther
off than the other, or even nearer This
is the case with Rigel, which mas "a
nnth-magnitude star close to it. The
measure showed that the faint star. far
from being behind the other, was actual
ly the nearer of the two. But by choos-
ing several small stars and mea surfing
from them all. this source of error can
be pretty well done away with.
The whole observed change of bearing
of the star is evidently equal to the
angular diameter of the earth's orbit.
as seen from the star. Half of this. or
the radius of the earth's orbit, as seen
The nearer q star is the greater its
parallaX will be. BY the methods OUT
lined above. the distances of a consider
able number of stars have been measured.
FlaaN Altsl,s
bic in our latitude) whose paralIaS~ is
three-QuarterS of n second of arc, oorre-
spending to a distance 10000 times as
great the suns. ..-
The NEST convenient unit for measur-
ing these great distances is the light
year-the distance light travels in year.
This is about 5000 times the suns dis
tance so that if we made a man on such
IA scale that the earth was one inch
from the sun. light-year would be rep
presented on the map by one mile. Alpha
Centauri is a little over four light-years
distant. Sirius, whose parallax is half
as great (O.37 sec.D is twice as far away.
If a star is over one hundred light-years
distant. its parallax is too small to be
rant of its true distance. This is the
case for some Of the very brightest stars,
and for the vast majority of the remain
der. For example, all the conspicuous
stars in Orion have no sensible parafldX.
All we ear say is that they must be
many times as far away as Sirius or
Procyon-how many, times we do not
know. But it follows that they must be
really much brighter than Sirius, which
if transported to SO great a distance
would at best be inconspicuous to the
naked eye. -t
Mercury is morning star until the 12tn,
but evening star before his passage
through superior conjunction on that
date. He is too near the sun to be seen.
Venus is evening star, and is also very
near the sun, though she may perhaps be
visible at the end of the MONTH when
she sets half an hour after sunset.
Mars is morning star in Virgo, and is
now rapidly gaining brightness. On the
I'D he is in quadrature with the sun, and
crosses the meridian at A. NJ. He is al
his greatest phase, and appears through
the telescope like the moon three days
from the full
Jupiter is evening star in. Capricornus,
setting about $50 p. NJ.
Saturn is evening star in Sagittarius,
setting at about p. NJ. 4-.... --
Uranus is in conjunction with the sur
on the 14th, and is invisible.
Neptune IS in opposition on the 24th.
His position on the 1St is in right asccn-
sion hours Il minutes 40 seconds, and
declnation p degrees is minutes Is Sec
onds north, while on the 31st it is right
ascension hours minutes Z seconds,
and declination % degrees II minutes q
seconds north. He can be seen with a
small telescope. though it takes a large
will aid in finding him, though. he can
only be certainly identified by his motion.
The moons first quarter occurs at A.
NJ h. Ctyx f,,IJ - 4