, 1908-05-09

ter's tow moons, and, how this discovery
led him to the certain conviction that Co.
pernicus was right in saying that our earth
revolved and that the sun was the real CEN
ire of our planetary system. The more pow
erful telescopes of modern times have re-
vealed the fact that Jupiter has more than
four moons. The fifth was discovered in 1892;
it is very small, only about 100 miles
in diameter, and is the innermost of the
moons.It is so near the planet that 1T has to
go around him ut q rapid rate, taking a triile
less than IL hours for an entire revolution.
Since then lin 1904 n sixth and lin 1909
a seventh moon have been discovered,
Early in the present year the attention Of
astronomers was called to "a small body Of
doubtful character which had bee seen
through the largest telescopes it might be
one Of that remarkable set OF small planets
between four and five hundred in nunber)
which occupy the grent gap between Mars
and Jupiter and go round the sun like the
larger planets, or it might be an eighth
moon of Jupiter. 1t seems now to have
been settled that the latter is the correct
Interpretation.
AS tie grcnt planet is in sight now every
n ght in our sky,a few words about him may
perhaps be found OF some interest. Three
months ago Ire was much brighter than he
- now, because we we're then at our nearest
to him. Now We are leaving him behind.
Then a common field glass could show one
or more of his moons, now it would pro-
badly require q very good field glass to see
them.
Looking for Jupiter, which is nearly over
lead at about eight o'clock in the evening,
our attention will be called to that richer
beauty of the evening SKY, Venus, which
will no GpQO fnItbnr yynaf Cho lOHl,J IUr,yf9
shan Jupiter bat in reality is very much
smaller, her advantage consisting in the
snallness of her distance from Us as COM
pared with thAt of Jupiter. Venus is vesy
nearly the same size rs this grand earth of
ours, but Jupiter measures about eleven
times as much across, SO that he is o Vori-
table giant by the side of Venus or the
Earth. Jupiter turns on his axis much fast
er than our earth against our period of "a
hours he takes hardly 10. One consequence
of this rapid motion is that the fAttening at
the poles amounts to one sixteenth of the
diameter, while the fattening of our earth is
only a three hundredth part, The surface
of the giant planet is full OF objects of in
terest to the astronomers. Belts of clouds
stretch around it parallel to its equator and
these present frequent changes.
The moons, however, and especially the
four large ones, are of the greatest practical
interest. In their passage around the planet
these become eclipsed rs they pass into the
shadow of the planet, AMI the times Of
these eclipses lin Greenwich tjme) are al
calculated in advance and entered in the
nautical almanac, and as they can be seen
wherever the planet is visible, they
form splendid time signals TO naviga-
tors in ali parts of the world. It was the
calculation of these eclipses which led to the
great discovery Of the Ye2ocity Of light, for
it was found that the actual eclipses were
earlier than the calculated times when the
planet was near md later when it was dis
tNnt.
We would recommend those of our rend-
era who may feel Interested, to notice the
movements of the mighty planet in the near
future. It will be found that his bright
ness will diminish and that he will APP
pear to move farther and farther westward
till he seems to be lost in the light OF the .
setting sun. When he next comes to view
again, it will be as q morning STIR, rising in
advance of the sun.