Jupiter

“ When we are thinking of worlds, and trying to exalt the imagination with them, it is well to turn to Jupiter, for there is a planet worth pondering upon! A world thirteen hundred times as voluminous as the earth is a phenomenon calculated to make us feel somewhat as the inhabitant of a rural village does when his amazed vision ranges across the million roofs of a metropolis. Jupiter is the first of the outer and greater planets, the major, or Jovian, group. His mean diameter is 86,500 miles, and his average girth more than 270,000 miles. ”

“ Jupiter’s entrance into any constellation immediately alters its familiar aspect, and he becomes its unquestioned leader, and remains such until his slow eastward motion carries him on to reign in another quarter of the firmament. He is never more impressive than when, in consequence of the annual revolution of the heavens, he rises late some night and takes the lingering star-gazer by surprise. ”

“ All this variety of tone and color makes of a telescopic view of Jupiter a picture that will not quickly fade from the memory; while if an instrument of considerable power is used, so that the wonderful details of the belts, with their scalloped edges, their diagonal filaments, their many divisions, and their curious light and dark spots, are made plain, the observer is deeply impressed with the strangeness of the spectacle, and the more so as he reflects upon the enormous real magnitude of that which is spread before his eye. ”

“ Passing thus close, Jupiter's stupendous cloud-belted sphere was an awe-inspiring sight, whirling at immense speed also, since the great planet, more than a thousand times greater than Earth, rotates upon its axis at hardly more than a third of Earth's rotatory period or day, its day being less than ten hours. ”

“ Even seen through a small telescope or pair of binoculars, Jupiter looks like a real world, displaying a faintly banded disk quite unlike the tiny, brilliant image of a star. It also reveals the brightest members of its satellite family as starlike points spread out along a straight line extended east-west through the planet. ”

“ Even those who have denied that Jupiter can be the abode of life, and have formed altogether unfavorable ideas of his condition, have pictured him nevertheless as the scene of continual calm, though the calm is, according to their view, the calm of gloom and desolation. They recognize in Jupiter an eternal winter rather than a perpetual spring. ”

“ Hebe, the goddess of Youth, mixed and poured out the Nectar, and Ganymede was Jupiter’s own page and cup-bearer. These gods and goddesses of the sky were a sort of large family, with Jupiter and Juno for father and mother. Of course Neptune with his gods of the sea, and Pluto with his gods of Hades, were like different families, and lived in their own places.
Whenever it thunders, that is the voice of Jupiter. One of the planets is named after him—it is a beautiful large white star. In pictures, he is a large, strong man, with a thick brown beard, looking like a king. ”

“ It is, of course, obvious that the heat of the planet is [Pg 257] inconsiderable when compared with the heat of the sun. The brilliance of Jupiter, which makes it an object of such splendour in our midnight sky, is derived from the same great source which illuminates the earth, the moon, or the other planets. Jupiter, in fact, shines by reflected sunlight, and not in virtue of any intrinsic light in his globe. A beautiful proof of this truth is familiar to every user of a telescope. The little satellites of the planet sometimes intrude between him and the sun, and cast a shadow on Jupiter. ”

“ For no one believes that heaven is heaven, no one keeps a fast, no one cares a hang about Jupiter: they all shut their eyes and count up their own profits. In the old days, the married women, in their stolas, climbed the hill in their bare feet, pure in heart, and with their hair unbound, and prayed to Jupiter for rain! ”

“ The cloudy aspect of Jupiter immediately strikes the telescopic observer. The huge planet is filled with color, and with the animation of constant movement, but there is no appearance of markings, like those on Mars, recalling the look of the earth. There are no white polar caps, and no shadings that suggest the outlines of continents and oceans. What every observer, even with the smallest telescope, perceives at once is a pair of strongly defined dark belts, one on either side of, and both parallel to, the planet's equator. ”

“ Passing over the asteroids, which are not very interesting objects to the amateur telescopist, we come to Jupiter, the giant of the solar system, surpassing our Earth more than 1400 times in volume, and overweighing all the planets taken together twice over.
Jupiter is one of the easiest of all objects of telescopic observation. No one can mistake this orb when it shines on a dark sky, and only Venus can be mistaken for it when seen as a morning or evening star. ”

“ Indeed, color and motion are so conspicuous in the immense spectacle presented by Jupiter that they impart to it a powerful suggestion of life, which the mind does not readily divest itself of when compelled to face the evidence that Jupiter is as widely different from the earth, and as diametrically opposed to lifelike conditions, as we comprehend them, as a planet possibly could be. ”

“ Giant Jupiter has an enormous realm—from the size of its satellite system to its tremendous aurorae and superbolts of lightning, to the huge planet-sized cloud features that surround its atmosphere. The most gargantuan Jovian feature is its magnetosphere, which envelopes the satellites and constantly changes in size, pumping in and out at the whim of the solar wind. The Pioneer and Voyager spacecraft provided four cuts through this dynamic region, showing that its borders in the upwind solar direction lie between 50 RJ and 100 RJ from Jupiter. ”

“ Although Jupiter appears to move slowly, it really travels at the incomprehensible rate of five hundred miles a minute.
The most interesting feature about Jupiter for the amateur astronomer consists in observing four of its moons, which are visible with a small telescope. They appear like mere dots of light, and their transit of or occultation with the planet (that is, their disappearance before or behind its disk) can be watched, and is a never failing source of pleasure. A large telescope alone reveals Jupiter's four other moons. ”

“ Neptune was appropriate as being the most remote planet. Now let us speak of Jupiter, the greatest planet. The day and night on Jupiter are both extremely short, for together they do not quite amount to ten hours. Jupiter's year, however, is almost twelve of our years. Although a man on Jupiter would only receive one-twenty-fifth part of the heat of the sun that he would do on the earth, yet it does not seem likely that there would be reason to apprehend that Jupiter would be uninhabitable from cold. ”

“ What you see is Jupiter's tremendous atmosphere belt. For some reason never satisfactorily explained, Jupiter's gaseous protective envelope is more than a thousand times deeper than that of any other planet. That's why Earth's astronomical instruments always show Jupiter's mass to be so tenuous; with a specific gravity, in fact, less than that of water. Jupiter is a gigantic cosmic fake; a huge bubble of semi-viscous atmosphere in the heart of which is embedded only a tiny, normal-sized core of the more cohesive elements which go to make up a planet. ”

“ But since ’tis certain that the Earth and Jupiter have their Water and Clouds, there is no Reason why the other Planets But not just like ours. should be without them. I can’t say that they are exactly of the same nature with our Water; but that they should be liquid their Use requires, as their Beauty does that they should be [28] clear. For this Water of ours, in Jupiter or Saturn, would be frozen up instantly by reason of the vast distance of the Sun. ”

“ The planet Jupiter, in fact, may justly be described as a miniature sun, vastly inferior in bulk to our own sun, inferior to a greater degree in heat, and in a greater degree yet in lustre, but to be compared with the sun—not with our earth—in size, in heat, and in lustre, and, lastly, in the tremendous energy of the processes which are at work throughout his cloud-laden atmospheric envelope. ”

“ It may, therefore, be regarded as certain that the globe of Jupiter, so far as we can see it, is not a solid body. It consists, on the exterior at all events, of clouds and vaporous masses, which seem to be agitated by storms of the utmost intensity, if we are to judge from the ceaseless changes of the planet's surface. ”

“ Jupiter has a favourable temperament, and is situated beneath the sphere of Saturn; he therefore occupies the next two signs, Sagittarius [Pg 29] and Pisces. These signs are airy and fruitful, in consequence of their trinal distance from the houses of the luminaries, which distance harmonises with the operation of good.
Mars is dry in nature, and beneath the sphere of Jupiter: he takes the next two signs, of a nature similar to his own, viz. Aries and Scorpio, whose relative distances from the houses of the luminaries are injurious and discordant. ”

“ Jupiter is the king, Jupiter himself is the original source of all things; there is one power, one god, and one great ruler over all. [21] But we have seen that Jupiter and all the other Gods were but names for the Sun; therefore it follows that the Sun, either as emblem or as God himself, was the object of universal adoration. ”

“ He is, indeed, not so very much heavier than a globe of water the same size would be, while our earth is five times as heavy as a globe of water equally large. The true explanation is that Jupiter is so swollen by these enormous masses of cloud which surround him as to give him a bigness altogether out of proportion to his mass. Therefore, as Mars gives us an illustration of the existence of oceans on other planets, so Jupiter provides us with a splendid example of a planet encompassed with clouds. ”

“ Without following the matter into any close numerical calculation, we may assert that for every one part the sun contributes to the common object, Jupiter will contribute at least a thousand parts; and this inequality appears all the more striking, not to say unjust, when it is remembered that the sun is more abundantly provided with moment of momentum than is Jupiter—the sun has, in fact, about twenty thousand times as much. ”

“ At the press briefing, Brad Smith made a spectacular announcement: “This morning I would like to add yet another important discovery to be claimed by this outstanding mission—that of a thin flat ring of particles surrounding Jupiter. Thus Jupiter now joins Saturn and Uranus to become the third planet of our solar system known to possess a planetary ring system and leaves Neptune as the only member of the group of giant planets without a known ring. ”

“ The rings of Jupiter are best seen when looking nearly in the direction of the Sun, since the small particles that comprise them are good forward scatterers of sunlight. This mosaic is of Voyager 2 images (two wide angle and four narrow angle) obtained from a perspective behind the planet and inside the shadow of Jupiter. The spacecraft was 2 degrees below the equator of Jupiter and 1.5 million kilometers from the rings. The shadow of the planet can be seen to obscure the near segment of the ring near the edge of the planet. ”

“ In Jupiter we have an illustration of a planet whose axis is almost at right angles to the plane of its orbit, being inclined but about a degree and a half. The hypothetical inhabitants of this majestic planet must therefore have perpetual summer at the equator, eternal winter at the poles, and in the temperate regions everlasting spring. ”

“ In looking at the real Jupiter, we on Earth are constantly changing our position as the Earth travels round the Sun; hence we can sometimes see the emergence and sometimes Jupiter blocks the way. You see the two kinds of blocking: he blocks the sunlight in one case, to make the eclipse; but he may also block the view from the Earth, if the Earth lies nearly in the same direction as the Sun. ”

“ It is to be remembered, however, that, whichever view we adopt, we must assume that a considerable portion of the light received, even from these portions of the planet's disk, must have been reflected sunlight. In fact, from what we know about the actual quantity of light received from Jupiter, we may be quite certain that no very large portion of that light is inherent. Jupiter shines about as brightly as if he were a giant cumulus-cloud, and therefore almost as white as driven snow. ”

“ As befits the king of the heavens, the planet Jupiter moves at a slow and stately pace. Twelve years are required for Jupiter to complete one orbit around the Sun. For about six months of each year, Jupiter shines down on us from the night sky, more brightly and steadily than any star. During the late 1970s it was a winter object, but in 1980 it will dominate the spring skies, becoming a summer “star” about 1982. ”

“ It appears to me demonstrated by the evidence thus far noted that in a semi-transparent atmosphere of enormous depth, surrounding Jupiter, there float vast cloud-masses, sometimes in layers, at others in irregular heaps, at others having well-rounded forms. These cloud-masses undergo sometimes remarkable changes of shape, often forming or disappearing in a very short time, and thus indicating the inferior activity of the forces at work below them—in other words, the intense heat of Jupiter's real globe. ”