Evening star. [volume] (Washington, D.C.) 1854-1972, 1904-10-29

| one of which revolveS around and around
the planet just as the moon revolves around
| the earth Each separate particle is far too
| small to be seen with the telescope, but
| there are so many of them that when they
are reviewed from the earth they appear
| as a continuous ring. At present we see
! the rings obliquely, as shown in figure =
| but sometimes the earth Is in such posi-
| ton that they are seen edgewlSe, as IN
! figure 3. This happens every fifteen years.
| 1t is then that the thickness of the
| rings is very small indeed, scarcely more
| than 100 miles. They are, in fact, so thin
| that DR.. Barnard of Chicago has seen one
| of the moons of saturn when it was be-
| hind the rings and shining directly through
| them. This would, of course have been
| impossible, had the rings been a solid
! mass
The Satellites.
Titan. the largest moon of Saturn, can
/ be seen even in a small telescope. 1t is
! about 1000 miles in diameter and passes
| completely around the planet in sixteen
days. Beside this moon, there are seven
| others, the inner one of which goes around
| the planet in less than one day, while the
| outer requires 10 days to make the circuit.
| In 1859 the surprising announcement was
| made from the Harvard observatory that
! a new satellite to Saturn had been discov-
| cred on delicate photograph of the planet.
| AS later photographs showed no trace of
this object, and as a most careful search
| failed to reveal it, it was supposed that
| PROBABLY 1t had no existence. NOW, now
| ever, it has been many times photographed
| again and even measured usually with the
| great Yerkes telescope at Chicago
The new body is of course excessively
| great, and more observations must be made
| of il before its motion can be computed very
| exactly. Il is already known, however, that
| this ninth moon occupies about a year and
q half in passing around the planet and that
it is more than eight millions of miles away
1roIp it.
The Planet Jupiter.
This planet is by far the brightest object
in the sky during the present month 1t will
be noticed al once, little east of south in
the constellation Pisces, in the position
marked on the map If examined with
small telescope, its appearance will be much
as shown in figure 4. The large ball of the
planet is seen, crossed by several very beau
tiful rose-colored bands, while nearby four
bright star-like objects will be detected;
these are the four moons of Jupiter
The moons revolve rapidly about the
planet, so that their relative positions are
continually changing. Sometimes one or
more of them pass behind the ball, are shut
rare occasions, none of them can be seen.
Jupiter then presents the appearance, very
peculiar to an astronomer, of being moon
less. When the light of a moon is thus cut
off the body does not remain invisible for
more than few hours at most; its rapid
motion about the planet soon brings it into
view again.
Jupiter. like Saturn, is an immense world
which is so hot that 1t is still in gaseous
or vaporiZed condition. 1t will be countless
ages before it shall have cooled down suf-
ficiently to make anything like life as We
know it possible on its surface. This great,
1eiy mass, more than $4,000 miles through,
turns on its axis very rapidly, making
complete rotation in nine hours and hfty-fve
minutes This means that a point on the
equator of the planet is carried through
ri 600 miles in ten hours, more than 4J0
miles a minute. The immense centrifugal
force arising from this rotation fiattens the
rlanet so that it is not perfectly round, and
also arranges the material of which it is
composed. in layers, or strata, parallel to
the planets equator. 1t is this which is the
cause of the bands of Jupiter
The Satellites.
In a large telescope the moons look like
little round disks which are passing around
the planet so quickly that they can even be
seen to move. The smallest of these is
about $500 miles in diameter and the larg-
est about $500. Their surfaces appear more
or less notified and banded. and white
spot has several times been seen near the
north pole of one of them. A fifth, very
small moon, was discovered by Dr Barnard
of Chicago in 1892.
Eclipses of Satellites.
Both Jupiter and Saturn are visible to us
simply because they reflect the sunlight
which falls on them; they do not apparently
emit any light of their own. The moons
also only look bright to US because they
are illumined by the light of the sun.
Stretching out behind each of the planets,
directly away from the sun. there is there
fore a large, conical shadow into which the
moons sometimes pass Whenever this &C.
ours the moon remains invisible to US until
it energies from the shadow into the sun
light again 1t is exactly in this same way
that an eclipse of our own moon is brought
about whenever our satellite passes into
the shadow of the earth.
One of Jupiter's moons will pass into his
shadow and suddenly become invisible on
the evening of November at three min
utes past Z; it will emerge again at twelve
minutes before .. On November 13 moon
will emerge from the shadow at ten min
uteS before Z, having entered it before sun
set, several hours earlier On the same
evening, at twenty-three minutes past s. a
moon will pass behind the planet and will
come out again into view at ten minutes
past 10. Another eclipse will occur later
this same night at five minutes past IL the
moon remaining invisible for one hour and
forty minutes. Any of these eclipses will
well repay observation. To see them salts
factorily a small telescope or a very good
field glass is required.
The November Meteors.
The November shooting stars should be
looked for In the northeast between mid
night and sunrise, on November 13, IA and
10. This is the most important shower of
the year. 1t is probable that altogether
several hundred of the stars will be seen to
fall during these three nights In 1893 the
sky was filled with these falling stars
more thickly than the air is filed with
snow flakes in a heavy storm. Unfortu-
nately, nothing like this is again looked for
1t is altogether probable that such extra
ordinary displays of the November meteors
have ceased. never to recur again.