Evening star. [volume] (Washington, D.C.) 1854-1972, 1905-12-30

Fig, 5.-Appearances of Jupter-s moons during
January
earth. from which it Is supposed that the
planet Is still intensely hot and in a gaseous
or vaporized state. 1t will be remembered
that Neptune was discovered by its pull on
the planet Uranus and that it's size and
position in the sky were known with perfect
accuracy before 1t had even been discovered
with the telescope. There is some evidence
that the motion of Neptune is being SINH
larly disturbed by a still more distant
planet, but Neptune moves so very slowly,
It's year being 1854 of years long, that
this question cannot be thoroughly inveSti-
gated for some time to come. If another
body is there there is not the slightest
doubt that 1t will some day be discovered
automatically, just as Neptune has been,
unless, indeed 1t is accidentally picked up
with the telescope. For this far-distant
world, whose journey around the sun may
occupy centuries, the appropriate name
Chronos. or the Tfmekeeper, has been sug
gested.
The stars marked D, in Fig. 2, are beau
tiful double stars; the one marked is a
triple and also varies in brightness about
one whole magnitude every ten days.
Jupiter's Westward Motion.
The planet Jupiter is still IN Taurus, be-
tween the Hyades and the Pleiades. Its
westward motion among the stars will
cease the oath Of the month and 1t will be.
planet Is now the most interesting object
in the sky TO the owner of a small tele-
scope The rose-tinted bands lying nearly
parallel to the equator and the great va
riety of irregular markings are plainly Wis
ible and will be seen rapidly shifting their
positions the planet turns on its axis
Near the planet there will be detected four
little points of Light which are the four
brightest moons of Jupiter. and these, too,
will be seen constantly altering their posi-
tons as the hours go by. The swiftly turn
ing planet with its retinue of satellites Is
one Of the most beautiful and interesting
of all the objects in the heavens.
The moons of Jupiter frequently pass be-
hind the planet and disappear from view.
Since Jupiter shines merely by reflected
sunlight, just as our moon does, 1t is at
tended by an enormous, condcal shadow
stretching out into space directly away
from the sun. The motion of the moons
frequently carries them into this shadow
and they are then eclipsed. Figure shows
on the proper scale this shadow with the
orbits of the moons of the planet. On
more moons may be seen to be eclipsed
by passing into this shadow. 1t was from
these eclipSeS that the velocity of light was
discovered by the Danish astronomer Roe
mer in 1873. Since the earth moves about
the sun in an orbit 1S5 millions of miles in
diameter, it follows that our distance from
Jupiter varies by just this amount Now
it is noticed that when we are nearest the
planet the eclipses of his moons occur In
SIN los early, and when we are farthest
away just SIN 19s late. AS we draw near
the planet the eclpses occur earlier and
earlier, and as we recede they fall more
and more behind time. Evidently this will
be fully accounted for by assuming that
the light by which we view the satellites
requires an appreciable time to make the
journey to us. 1t is found that when we
increase our distance from Jupiter 1856 Co.,
coo miles the eclipses occur Just lem 3ss
late, from which the velocity of light is
found to be 1S6, 800 miles per second
Figure shows the moons as they will
appear at 10 o'clock p. M, eastern time
on six different dates during the month IT
Will be noticed that on the 18th, 25th and
5oth the outer moon is at a great distance
from the planet. In a small telescope or
even in a good pair of opera glasses. it will
then be clearly visible.
The New Comet.
On November II bright new comet was
discovered by DR.. Schaer OF Geneva, Swift
zerland 1t was then within four degrees
OF the North Pole of the heavens. and in
extraordinarily rapid motion, so that bv
december 1t had passed entirely across
the sky to point below the equator The
path of this body between November II and
December is shown in figure /. It was a
small, round, woolly object without any
tail, which had passed around the SIM On
october 49, and is now rapidly recedinp
from US. Unfortunately at the time this
paper is written December a. its rnotion
during January cannot be predicted.