The morning call., 1891-08-31
THE PLANET JUPITER.
The Vastness and the Mysteries
of the Heavenly Bodies.
What Constitutes the Belts Of Jupiter-Ana'
lytical Exposition Of Various Phe-
nomena-A Word PIanetarium.
No doubt most of our readers have noticed


the extraordinarily bright star which has
been rising in the southeast late in the even
ing for some months past, and which now
puts in an appearance about o'clock. If
so, their curiosity has been probably stimu-
lated about it, as was that of CALL re-
porter recently. The reporter proceeded to
interview a gentleman connected with the
University of California, who is quite an
enthusiastic amateur astronomer.
$50 you want TO know something about
Jupiter" said he. 'N ell. am not surprised
at it, for several Of my friends have already
asked me to tell them what that extraordi-
narily bright object they saw in the east
was. And this illustrates, by the way, how
little attention most people pay TO the sky,
for Jupiter was very nearly as bright and
conspicuous last year about this time; yet to
hear most people talk one would think he
had never appeared before.
Jupiter, just now, is approaching appo-
sition, that is, on the 9th of September the
earth will be between Jupiter and the sun,
and almost exactly on a line from one of
them to the other, the distance from Il e
earth to piter being almost four times the
distance from the earth to the sun. If he
orbits of these two planets were exactly
| circular they would, of course, be Mt their
shortest distance then, but their orbits are
more or less elliptical, so that at different
| appostions their distances are slightly diff
| ferent. The favorable appositions are those
| that occur in October, AMI such one Will
come in 1892. IL will also be much more IA
vorable than the one Of this year for another
reason. Jupiter is so far to the south now
that he never rises more than about 4jo
| above the horizon, though any one looking
| at him when on the meridian would be al
| most certain to t-ink his altitude greater.
| But next year he will have advanced far
| ther to the north, that his highest alti-
| tude will be nearly 60', which is about equal
| TO that of tile sun at noon during the first
| week If September. This will give the as
| tronomers a much better chance at him, for
| no matter what the size of the telescope
| (unlesS mere spy-glass), or how good the
| night, a telescope has not n chance TO exert
| its full powers upon an object unless that
| object is near the zenith. Twenty degrees
| from the zenith is very good position; 10o
| is much better and directly overhead is
| BEsT OF ALL.o
primarily, this is due to the fact that the
| nearer an object is to the horizon the more
| air there is to look through; that Is, near
| the horizon the trembling in the air be-
| comes much more conspicuous, and the at
| moSphere also cuts off much more light. If
| anyone wants to get better idea OF this, let
| him look al the milky way on clear moon
| less night. Near the horizon the milky Way
l
| will twinkle a great deal. while overhead
everything will appear beautifully bright
and there will be very little twinkling The
| opposition of November S, 1898. will be es-
| pecially favorable in this respect, for the
| planet. While being very little farther from
the earth than when at its nearest will have
| an altitude of 100 at midnight.
| Professor Young of Princeton says of
| Jupiter: Even i'll small telescope the
| planet is a beautiful object. When near
| of
| forty makes its apparent size equal to that
| of the full moon Though no novice would
| receive that impreSson), and with a tele-
| scope of eight or ten inches aperture, and
| with magnlfylng power of three or four
| hundred, the disc is covered with an infinite
variety of beautiful and interesting details
which rapidly shift under the Observers eye
in consequence of the planets swift
rotation. Tue. picture is rich in
color, also, browns and reds pre-
| greens and occasional purples; but to
bring out the cOlors well and clearly
requires large instruments. For the most
| part the markings are arranged in streaks
more or less parallel to the planets equator.
| With small telescope the markings usually
| reduce to two dark and comparatively we'll
| defined belts, one on each side of the
| equator, occupying about the same region OF
| latitude that the trade-wind zones do upon
| the earth; and very likely in Jupiter'S case
similar aerial currents have something TO do
| with the appearance, though upon Jupiter
| the solar heat is q comparatively unlmpOr-
tant factor. The markings upon the planet
| are almost, If not entirely, atmospheric, as is
proved by the manner in which they change
| their shapes and relative positions. They
are cloud forms. 1t is hardly probable that
we ever see anything upon the solid surface
of the planet beneath, nor is 1t even certain
the planet has anything solid about it,
PROFESSOR YoUNG's REMARK
4
duce to two dark belts refers to very small
telescope indeed, for they are distinctly
visible in my two-inch spy-glass. | have
seen some very fine drawings of Jupiter
that were made with a 3 E2-inch telescope at
Nashville by Professor Barnard, now at the
| Lick observatory.
"The statement that a power of forty
makes Jupiter appear as large as the full
moon is strictly accurate. But it must be
remembered that magnfying Jupiter to the
moons size does not bring it as near "a the
moon, for Jupiters diameter $4,000 niles
is forty times as great ais the moons, SO
that it needs, at opposition, a power of
about 1900 to bring it to the moons distance.
A lower power than this Will sometimes do
it, fer Jupiter when ut his nearest is 369-
600, 600 miles away; the moons average dis
tance is 100000 miles; dividing the first by
the second gives 1910, or: the magnifying
power required.
Jupiter, as all probably know, has four
| moons. Win q power Vi lUU ulHiHbIeTS III Is
barely possible on a good night 10 see their
round discs with lower powers they are
mere points of light like stars; 200 dame
ters make their discs very distinct, but with
a power of 1900 the smallest of them would
appear as large as our full moon. If it were
possible to see as we'll with this power as
We see our moon with the naked eye, moth
| ing more would he desired, for there is a
| really wonderful amount OF detail visible on
the moon, with unaided vision. All the
1os.. I1-1 1lfN neA ha 4
| out, and so can at least three of the princi-
| pal craters, the latter appearing as white
| spots. But let US see how well one of Jupi-
ter's satellites would show up under a mag
uification OF 1000 dlameters, even with per-
1 feet atmospherical conditions. There is
only one telescope in the world which is
large enough and well enough situated to
allow the use of SO high power on the
planets. and that is the great 36-inch tele-
scope at the Lick Observatory. With a
| power of 180 the surface of an object would
appear as bright as it does 10 the naked eye,
were there no loss of light in the telescope ;
in reality, it would only be four-fifths as
| bright. We would have to multiply this
power by nine to get power Of 1900; this
| would make surface appear only one
hundredth part as bright as it really ls. The
| brightest OF
| JUPTER's SATELLITES
| Has surface only one-seventh part as
| bright as that of our own moon, so that
| with such a power we would see its surface
only one seven hund edith part as bright as
we see that of our moon with the naked
eye. The reason for this is that while the
great lens collects 26000 times as much
light as the pupil Of the eye theoretically
80, 400 times as much), magnifying power
of 1900 diameters spreads this amount of
light over all area one hundred times 26 600
times as great about as we see it with the
naked eye. This can be readily proved by
sQuaring 1900.
But this does not prove that such a
| power could not be used under sufficiently
favorable conditions (as on a strictly first
class aAight in November, 1898, and | can
readily show 1t. The surface of the planet
Saturn is only about one thirty-third part as
bright as that of our moon, or about one
fifth part as bright as that of one of Jupi-
ter's satellites. Yet one night in March,
1889. Professors Holden and Schaebere, at
| the Lick OhserYatnrY aYamined Saturn