SATURN.
The system of Jupiter is a simple system compared with that of Saturn,
next in order. For whereas Jupiter has only five moons, Saturn has
eight, and, in addition to these, he has three wonderful rings. Neither
rings nor moons can be seen without a telescope, on account of Saturn’s
great distance from us--more than three thousand times the distance of
the moon, or upwards of eight hundred millions of miles. Saturn’s mean
distance from the sun is eight hundred and seventy-six million seven
hundred and sixty-seven thousand miles.
Saturn does not equal his mighty brother Jupiter in size, though he
comes near enough in this respect to be called often his “twin”--just
as that small pair of worlds, Venus and Earth, are called “twins.”
While Jupiter is equal in size to over one thousand two hundred earths,
Saturn is equal to about seven hundred earths. And while Jupiter is
equal in weight to three hundred earths, Saturn is only equal in weight
to ninety earths. He appears to be made of very light materials--not
more than three-quarters as dense as water. This would show the present
state of Saturn to be very different from the present state of the
earth. We are under the same uncertainty in speaking of Saturn as in
speaking of Jupiter. Like Jupiter, Saturn is covered with dense masses
of varying clouds, occasionally opening and allowing the astronomer
peeps into lower cloud-levels; but rarely or never permitting the
actual body of the planet to be seen.
The same perplexities also come in here, to be answered much in the
same manner. We should certainly expect that in a vast globe like
Saturn the strong force of attraction would bind the whole into a
dense solid mass; instead of which, Saturn is about the least solid of
all the planets. He seems to be made up of a light, watery substance,
surrounded by vapor.
[Illustration: SATURN AND THE EARTH--COMPARATIVE SIZE.]
One explanation can be offered. What if the globe of Saturn be still
in a red-hot, molten state, keeping such water as would otherwise lie
in oceans on his surface, floating aloft in masses of steam, the outer
parts of which condense into clouds?
No one supposes that Jupiter and Saturn are in the same condition
of fierce and tempestuous heat as the sun. They may have been so
once, but they must now have cooled down very many stages from that
condition. Though no longer, however, a mass of far-reaching flames and
fiery cyclones, the body of each may have only so far cooled as to have
reached a stage of glowing molten red-heat, keeping all water in the
form of vapor, and sending up strong rushes of burning air to cause the
hurricanes which sweep to and fro the vast cloud-masses overhead.
And if this be the case, then, with Saturn as with Jupiter, comes the
question, Can Saturn be inhabited? And if--though we may not say it is
impossible, yet we feel it to be utterly unlikely--then again follows
the question, What if Saturn’s _moons_ are inhabited?
Telescopic observations tempt us to believe that there is on this
planet a quantity of heat greater than that which results from its
distance from the sun; for the day-star as seen from Saturn is, as we
have said, ninety times smaller in surface, and its heat and light
are reduced in the same proportion. Water could only exist in the
solid state of ice, and the vapor of water could not be produced so
as to form clouds similar to ours. Now, meteorological variations are
observed similar to those which we have noticed on Jupiter, but less
intense. Facts, then, combine with theory to show us that the world of
Saturn is at a temperature at least as high as ours, if not higher.
But the strangest feature of the Saturnian calendar is, unquestionably,
its being complicated, not only with the fabulous number of 25,060
days in a year, but, further, with eight different kinds of months, of
which the length varies from 22 hours to 79 days--that is to say, from
about two Saturnian days to 167. It is as if we had here _eight moons
revolving in eight different periods_.
The inhabitants of such a world must assuredly differ strangely
from us from all points of view. The specific lightness of the
Saturnian substances and the density of the atmosphere will have
conducted the vital organization in an extra-terrestrial direction,
and the manifestations of life will be produced and developed under
unimaginable forms. To suppose that there is nothing fixed, that the
planet itself is but a skeleton, that the surface is liquid, that the
living beings are gelatinous--in a word, that all is unstable--would be
to surpass the limits of scientific induction.
The diameter of the largest moon is about half the diameter of the
earth, or much larger than Mercury. The four inner satellites are
all nearer to Saturn than our moon to us, though the most distant of
the eight is ten times as far away. The inner moon takes less than
twenty-three hours to travel round Saturn, and the outer one over
seventy-nine days.
A great many charming descriptions have been worked up, with Saturn
as with Jupiter, respecting the magnificent appearance of the eight
radiant moons, joined to the glorious shining of the rings, as quite
making up for the diminished light and heat of the sun. But here again
comes in the doubt, whether really it is the moons who make up to
Saturn for lack of light, or whether it is Saturn who makes up to the
moons for lack of light.
Certainly, Saturn’s cloudy covering would a little interfere with
observations of the moons by any inhabitants of the solid body
within--supposing there be any solid body at all. And though it sounds
very wonderful to have eight moons instead of one moon, yet all the
eight together give Saturn only a very small part of the light which we
receive from our one full moon--so much more dimly does the sun light
them up at that enormous distance.
The same thing has been noticed with Saturn as with Jupiter--that he
seems to shine more brightly than is to be expected in his position,
from mere reflection of the sun’s rays. A glowing body within, sending
a certain amount of added light through or between the masses of
clouds, would explain away this difficulty.
One more possible proof of Saturn’s half-liquid state is to be found
in his occasional very odd changes of shape. Astronomers have been
startled by a peculiar bulging out on one side, taking off from his
roundness, and giving a square-shouldered aspect. We may not say it
is quite impossible that a solid globe should undergo such tremendous
upheavals and outbursts as to raise a great portion of its surface five
or six hundred miles above the usual level--the change being visible
at a distance of eight hundred millions of miles. But it would be
easier to understand the possibility of such an event, in the case of a
liquid, seething mass, than in the case of a solid ball.
On the other hand this alteration of outline may be caused simply by
a great upheaval not of the planet’s surface, but of the overhanging
layers of clouds. Some such changes, only much slighter, have been
remarked in Jupiter.
And now as to the rings. Nothing like them is to be seen elsewhere in
the Solar System. They are believed to be three in number; though some
would divide them into more than three. Passing completely round the
whole body of Saturn, they rise, one beyond another, to a height of
many thousands of miles.
The inner edge of the inner ring--an edge perhaps one hundred miles in
thickness--is more than ten thousand miles from the surface of Saturn
or more strictly speaking, from the outer surface of Saturn’s cloudy
envelope. A man standing exactly on the equator and looking up, even if
no clouds came between, would scarcely be able to see such a slender
dark line at such a height.
This dark, transparent ring, described sometimes as dusky, sometimes as
richly purple, rises upwards to a height or breadth of nine thousand
miles. Closely following it is a ring more brilliant than Saturn
himself, over eighteen thousand miles in breadth. When astronomers talk
of the “breadth” of these rings, it must be understood that they mean
the width of the band measured _upwards_, in a direction away from the
planet.
Beyond the broad, bright ring is a gap of about one thousand seven
hundred miles. Then follows the third ring, ten thousand miles in
breadth; its outermost edge being at a height of more than forty-eight
thousand miles from Saturn. The color of the third ring is grayish,
much like the gray markings often seen on Saturn.
What would not be our admiration, our astonishment, our stupor perhaps,
if it were granted us to be transported there alive, and, among all
these extra-terrestrial spectacles, to contemplate the strange aspect
of the rings, which stretch across the sky like a bridge suspended
in the heights of the firmament! Suppose we lived on the Saturnian
equator itself, these rings would appear to us as a thin line drawn
across the sky above our heads, and passing exactly through the zenith,
rising from the east and increasing in width, then descending to the
west and diminishing according to perspective. Only there have we
the rings precisely in the zenith. The traveler who journeys from
the equator towards either pole leaves the plane of the rings, and
these sink imperceptibly, at the same time that the two extremities
cease to appear diametrically opposite, and by degrees approach each
other. What an amazing effect would be produced by this gigantic
arch, which springs from the horizon and spans the sky! The celestial
arch diminishes in height as we approach the pole. When we reach the
sixty-third degree of latitude the summit of the arch has descended to
the level of our horizon and the marvelous system disappears from the
sky; so that the inhabitants of those regions know nothing of it, and
find themselves in a less favorable position to study their own world
than we, who are nearly 800,000,000 miles distant.
During one-half of the Saturnian year the rings afford an admirable
moonlight on one hemisphere of the planet, and during the other half
they illuminate the other hemisphere; but there is always a half-year
without “ringlight,” since the sun illuminates but one face at a time.
Notwithstanding their volume and number, the satellites do not give
as much nocturnal light as might be supposed; for they receive, on an
equal surface, only the ninetieth part of the solar light which our
moon receives. All the Saturnian satellites which can be at the same
time above the horizon and as near as possible to the full phase do not
afford more than the hundredth part of our lunar light. But the result
may be nearly the same, for the optic nerve of the Saturnians may be
ninety times more sensitive than ours.
But there are further strange features in this system. The rings are
so wide that their shadow extends over the greater part of the mean
latitudes. During fifteen years the sun is to the south of the rings,
and for fifteen years it is to the north. The countries of Saturn’s
world which have the latitude of Paris endure this shadow for more than
five years. At the equator the eclipse is shorter, and is only renewed
every fifteen years; but there are every night, so to say, eclipses of
the Saturnian moons by the rings and by themselves. In the circumpolar
regions the day-star is never eclipsed by the rings; but the satellites
revolve in a spiral, describing fantastic rounds, and the sun himself
disappears at the pole during a long night of fifteen years.
At one time it was supposed that the rings were solid, but they are now
believed to consist of countless myriads of meteorites, each whirling
in its own appointed pathway round the monster planet.
[Illustration: IDEAL VIEW OF SATURN’S RINGS AND SATELLITES FROM THE
PLANET.]
As already said--leaving out of the question the cloudy atmosphere--a
man standing on the equator would see nothing of the rings. A man
standing at the north pole or the south pole of Saturn could see
nothing either, since the rings would all lie below his horizon. But
if he traveled southward from the north pole, or northward from the
south pole, towards the equator, he would in time see the ringed arch
appearing above the horizon, rising higher and growing wider with every
mile of his journey; and when he was in a position to view the whole
broad expanse, the transparent half-dark belt below, the wide radiant
band rising upwards over that, and the grayish border surmounting all,
he would truly have a magnificent spectacle before him.
This magnificent spectacle is, however, by no means always visible,
even from those parts of Saturn where alone it ever can be seen. The
rings shine merely by reflected sunlight. Necessarily, therefore, while
the sunbeams make one side bright the other side is dark; and not only
this, but the rings throw broad and heavy shadows upon Saturn in the
direction away from the sunlight.
In the daytime they probably give out a faint shining, something like
our own moon when seen in sunlight. During the summer nights they
shine, no doubt, very beautifully. During the winter nights it so
happens that their bright side is turned away; and not only that, but
during the winter days the rings, while giving no light themselves to
the wintry hemisphere of Saturn, completely hide the sun.
When it is remembered that Saturn’s winter--that is, the winter of each
hemisphere in turn--lasts during fifteen of our years; and when we hear
of total eclipses of the sun lasting unbroken through eight years of
such a winter, with not even bright rings to make up for his absence,
we can not think of Saturn as a tempting residence. The sun gives
Saturn at his best only about one-ninetieth of the heat and light that
he gives to our earth; but to be deprived of even that little for eight
years at a time, does indeed sound somewhat melancholy.
Looking now at the other side of the question, the possible inhabitants
of the moons, especially those near at hand, would have splendid views
of Saturn and his rings in all their varying phases. For Saturn is a
beautiful globe, wrapped in his changeful envelope of clouds, which,
seen through a telescope, are lit up often with rainbow tints of blue
and gold; a creamy white belt lying usually on the equator; while
around extend the purple and shining and gray rings, sometimes rivaling
in bright colors Saturn himself.
We are compelled to assume that the continuous appearance of the rings
is not due to real continuity of substance, but that they are composed
of flights of disconnected satellites, so small and so closely packed
that, at the immense distance to which Saturn is removed, they appear
to form a continuous mass. There are analogous instances in the Solar
System. In the zone of asteroids we have an undoubted instance of a
flight of disconnected bodies traveling in a ring about a central
attracting mass. The existence of zones of meteorites traveling around
the sun has long been accepted as the only probable explanation of the
periodic returns of meteoric showers. Again, the singular phenomenon
called the Zodiacal Light is, in all probability, caused by a ring of
minute cosmical bodies surrounding the sun. In the Milky Way and in
the ring-nebulæ we have other illustrations of similar arrangements
in nature, belonging, however, to orders immeasurably vaster than any
within the Solar System.
The moons of Saturn do not, like those of Jupiter, travel in one plane.