The Passing of the Constellations

From a historical and picturesque point of view, one of the most striking results of the motions of the stars described in the last chapter is their effect upon the forms of the constellations, which have been watched and admired by mankind from a period so early that the date of their invention is now unknown. The constellations are formed by chance combinations of conspicuous stars, like figures in a kaleidoscope, and if our lives were commensurate with the æons of cosmic existence we should perceive that the kaleidoscope of the heavens was ceaselessly turning and throwing the stars into new symmetries. Even if the stars stood fast, the motion of the solar system would gradually alter the configurations, as the elements of a landscape dissolve and recombine in fresh groupings with the traveler’s progress amid them. But with the stars themselves all in motion at various speeds and in many directions, the changes occur more rapidly. Of course, “rapid” is here understood in a relative sense; the wheel of human history to an eye accustomed to the majestic progression of the universe would appear to revolve with the velocity of a whirling dynamo. Only the deliberation of geological movements can be contrasted with the evolution and devolution of the constellations.

And yet this secular fluctuation of the constellation figures is not without keen interest for the meditative observer. It is another reminder of the swift mutability of terrestial affairs. To the passing glance, which is all that we can bestow upon these figures, they appear so immutable that they have been called into service to form the most lasting records of ancient thought and imagination that we possess. In the forms of the constellations, the most beautiful, and, in imaginative quality, the finest, mythology that the world has ever known has been perpetuated. Yet, in a broad sense, this scroll of human thought imprinted on the heavens is as evanescent as the summer clouds. Although more enduring than parchment, tombs, pyramids, and temples, it is as far as they from truly eternizing the memory of what man has fancied and done.

Before studying the effects that the motions of the stars have had and will have upon the constellations, it is worth while to consider a little further the importance of the stellar pictures as archives of history. To emphasize the importance of these effects it is only necessary to recall that the constellations register the oldest traditions of our race. In the history of primeval religions they are the most valuable of documents. Leaving out of account for the moment the more familiar mythology of the Greeks, based on something older yet, we may refer for illustration to that of the mysterious Maya race of America. At Izamal, in Yucatan, says Mr Stansbury Hagar, is a group of ruins perched, after the Mexican and Central-American plan, on the summits of pyramidal mounds which mark the site of an ancient theogonic center of the Mayas. Here the temples all evidently refer to a cult based upon the constellations as symbols. The figures and the names, of course, were not the same as those that we have derived from our Aryan ancestors, but the star groups were the same or nearly so. For instance, the loftiest of the temples at Izamal was connected with the sign of the constellation known to us as Cancer, marking the place of the sun at the summer solstice, at which period the sun was supposed to descend at noon like a great bird of fire and consume the offerings left upon the altar. Our Scorpio was known to the Mayas as a sign of the “Death God.” Our Libra, the “Balance,” with which the idea of a divine weighing out of justice has always been connected, seems to be identical with the Mayan constellation Teoyaotlatohua, with which was associated a temple where dwelt the priests whose special business it was to administer justice and to foretell the future by means of information obtained from the spirits of the dead. Orion, the “Hunter” of our celestial mythology, was among the Mayas a “Warrior,” while Sagittarius and others of our constellations were known to them (under different names, of course), and all were endowed with a religious symbolism. And the same star figures, having the same significance, were familiar to the Peruvians, as shown by the temples at Cuzco. Thus the imagination of ancient America sought in the constellations symbols of the unchanging gods.

But, in fact, there is no nation and no people that has not recognized the constellations, and at one period or another in its history employed them in some symbolic or representative capacity. As handled by the Greeks from prehistoric times, the constellation myths became the very soul of poetry. The imagination of that wonderful race idealized the principal star groups so effectively that the figures and traditions thus attached to them have, for civilized mankind, displaced all others, just as Greek art in its highest forms stands without parallel and eclipses every rival. The Romans translated no heroes and heroines of the mythical period of their history to the sky, and the deified Cæsars never entered that lofty company, but the heavens are filled with the early myths of the Greeks. Herakles nightly resumes his mighty labors in the stars; Zeus, in the form of the white “Bull,” Taurus, bears the fair Europa on his back through the celestial waves; Andromeda stretches forth her shackled arms in the star-gemmed ether, beseeching aid; and Perseus, in a blaze of diamond armor, revives his heroic deeds amid sparkling clouds of stellar dust. There, too, sits Queen Cassiopeia in her dazzling chair, while the Great King, Cepheus, towers gigantic over the pole. Professor Young has significantly remarked that a great number of the constellations are connected in some way or other with the Argonautic Expedition—that strangely fascinating legend of earliest Greek story which has never lost its charm for mankind. In view of all this, we may well congratulate ourselves that the constellations will outlast our time and the time of countless generations to follow us; and yet they are very far from being eternal. Let us now study some of the effects of the stellar motions upon them.

We begin with the familiar figure of the “Great Dipper.” He who has not drunk inspiration from its celestial bowl is not yet admitted to the circle of Olympus. This figure is made up of seven conspicuous stars in the constellation Ursa Major, the “Greater Bear.” The handle of the “Dipper” corresponds to the tail of the imaginary “Bear,” and the bowl lies upon his flank. In fact, the figure of a dipper is so evident and that of a bear so unevident, that to most persons the “Great Dipper” is the only part of the constellation that is recognizable. Of the seven stars mentioned, six are of nearly equal brightness, ranking as of the second magnitude, while the seventh is of only the third magnitude. The difference is very striking, since every increase of one magnitude involves an increase of two-and-a-half times in brightness. There appears to be little doubt that the faint star, which is situated at the junction of the bowl and the handle, is a variable of long period, since three hundred years ago it was as bright as its companions. But however that may be, its relative faintness at the present time interferes but little with the perfection of the “Dipper’s” figure. In order the more readily to understand the changes which are taking place, it will be well to mention both the names and the Greek letters which are attached to the seven stars. Beginning at the star in the upper outer edge of the rim of the bowl and running in regular order round the bottom and then out to the end of the handle, the names and letters are as follows: Dubhe (α), Merak (β), Phaed (γ), Megrez (δ), Alioth (ε), Mizar (ζ), and Benetnasch (η). Megrez is the faint star already mentioned at the junction of the bowl and handle, and Mizar, in the middle of the handle, has a close, naked-eye companion which is named Alcor. The Arabs called this singular pair of stars “The Horse and Rider.” Merak and Duhbe are called “The Pointers,” because an imaginary line drawn northward through them indicates the Pole Star.

Now it has been found that five of these stars—viz., Merak, Phaed, Megrez, Alioth, and Mizar (with its comrade)—are moving with practically the same speed in an easterly direction, while the other two, Dubhe and Benetnasch, are simultaneously moving westward, the motions of Benetnasch being apparently more rapid. The consequence of these opposed motions is, of course, that the figure of the “Dipper” cannot always have existed and will not continue to exist. In the accompanying diagrams it has been thought interesting to show the relative positions of these seven stars, as seen from the point which the earth now occupies, both in the past and in the future. Arrows attached to the stars in the figure representing the present appearance of the “Dipper” indicate the directions of the motions and the distances over which they will carry the stars in a period of about five hundred centuries. The time, no doubt, seems long, but remember the vast stretch of ages through which the earth has passed, and then reflect that no reason is apparent why our globe should not continue to be a scene of animation for ten thousand centuries yet to come. The fact that the little star Alcor placed so close to Mizar should accompany the latter in its flight is not surprising, but that two of the principal stars of the group should be found moving in a direction directly opposed to that pursued by the other five is surprising in the highest degree; and it recalls the strange theory of a double drift affecting all the stars, to which attention was called in the preceding chapter. It would appear that Benetnasch and Dubhe belong to one “current,” and Merak, Phaed, Megrez, Alioth, and Mizar to the other. As far as is known, the motion of the seven stars are not shared by the smaller stars scattered about them, but on the theory of currents there should be such a community of motion, and further investigation may reveal it.

From the “Great Dipper” we turn to a constellation hardly less conspicuous and situated at an equal distance from the pole on the other side—Cassiopeia. This famous star-group commemorating the romantic Queen of Ethiopia whose vain boasting of her beauty was punished by the exposure of her daughter Andromeda to the “Sea Monster,” is well-marked by five stars which form an irregular letter “W” with its open side toward the pole. Three of these stars are usually ranked as of the second magnitude, and two of the third; but to ordinary observation they appear of nearly equal brightness, and present a very striking picture. They mark out the chair and a part of the figure of the beautiful queen. Beginning at the right-hand, or western, end of the “W,” their Greek letter designations are: Beta (β), Alpha (α), Gamma (γ), Delta (δ), and Epsilon (ε). Four of them, Beta, Alpha, Delta, and Epsilon are traveling eastwardly at various speeds, while the fifth, Gamma, moves in a westerly direction. The motion of Beta is more rapid than that of any of the others. It should be said, however, that no little uncertainty attaches to the estimates of the rate of motion of stars which are not going very rapidly, and different observers often vary considerably in their results.

In the beautiful “Northern Crown,” one of the most perfect and charming of all the figures to be found in the stars, the alternate combining and scattering effects of the stellar motions are shown by comparing the appearance which the constellation must have had five hundred centuries ago with that which it has at present and that which it will have in the future. The seven principle stars of the asterism, forming a surprisingly perfect coronet, have movements in three directions at right angles to one another. That in these circumstances they should ever have arrived at positions giving them so striking an appearance of definite association is certainly surprising; from its aspect one would have expected to find a community of movement governing the brilliants of the “Crown,” but instead of that we find evidence that they will inevitably drift apart and the beautiful figure will dissolve.

A similar fate awaits such asterisms as the “Northern Cross” in Cygnus; the “Crow” (Corvus), which stands on the back of the great “Sea Serpent,” Hydra, and pecks at his scales; “Job’s Coffin” (Delphinus); the “Great Square of Pegasus”; the “Twins” (Gemini); the beautiful “Sickle” in Leo; and the exquisite group of the Hyades in Taurus. In the case of the Hyades, two controlling movements are manifest: one, affecting five of the stars which form the well-known figure of a letter “V,” is directed northerly; the other, which controls the direction of two stars, has an easterly trend. The chief star of the group, Aldebaran, one of the finest of all stars both for its brilliance and its color, is the most affected by the easterly motion. In time it will drift entirely out of connection with its present neighbors. Although the Hyades do not form so compact a group as the Pleiades in the same constellation, yet their appearance of relationship is sufficient to awaken a feeling of surprise over the fact that, as with the stars of the “Dipper,” their association is only temporary or apparent.

The great figure of Orion appears to be more lasting, not because its stars are physically connected, but because of their great distance, which renders their movements too deliberate to be exactly ascertained. Two of the greatest of its stars, Betelgeuse and Rigel, possess, as far as has been ascertained, no perceptible motion across the line of sight, but there is a little movement perceptible in the “Belt.” At the present time this consists of an almost perfect straight line, a row of second-magnitude stars about equally spaced and of the most striking beauty. In the course of time, however, the two right-hand stars, Mintaka and Alnilam (how fine are these Arabic star names!) will approach each other and form a naked-eye double, but the third, Alnita, will drift away eastward, so that the “Belt” will no longer exist.

For one more example, let us go to the southern hemisphere, whose most celebrated constellation, the “Southern Cross,” has found a place in all modern literatures, although it has no claim to consideration on account of association with ancient legends. This most attractive asterism, which has never ceased to fascinate the imagination of Christendom since it was first devoutly described by the early explorers of the South, is but a passing collocation of brilliant stars. Yet even in its transfigurations it has been for hundreds of centuries, and will continue to be for hundreds of centuries to come, a most striking object in the sky. Our figures show its appearance in three successive phases: first, as it was fifty thousand years ago (viewed from the earth’s present location); second, as it is in our day; and, third, as it will be an equal time in the future. The nearness of these bright stars to one another—the length of the longer beam of the “Cross” is only sixdegrees—makes this group very noticeable, whatever the arrangement of its components may be. The largest star, at the base of the “Cross,” is of the first magnitude, two of the others are of the second magnitude, and the fourth is of the third. Other stars, not represented in the figures, increase the effect of a celestial blazonry, although they do not help the resemblance to a cross.

But since the motion of the solar system itself will, in the course of so long a period as fifty thousand years, produce a great change in the perspective of the heavens as seen from the earth, by carrying us nearly nineteen trillion miles from our present place, why, it may be asked, seek to represent future appearances of the constellations which we could not hope to see, even if we could survive so long? The answer is: Because these things aid the mind to form a picture of the effects of the mobility of the starry universe. Only by showing the changes from some definite point of view can we arrive at a due comprehension of them. The constellations are more or less familiar to everybody, so that impending changes of their forms must at once strike the eye and the imagination, and make clearer the significance of the movements of the stars. If the future history of mankind is to resemble its past and if our race is destined to survive yet a million years, then our remote descendents will see a “new heavens” if not a “new earth,” and will have to invent novel constellations to perpetuate their legends and mythologies.

If our knowledge of the relative distances of the stars were more complete, it would be an interesting exercise in celestial geometry to project the constellations probably visible to the inhabitants of worlds revolving around some of the other suns of space. Our sun is too insignificant for us to think that he can make a conspicuous appearance among them, except, perhaps, in a few cases. As seen, for instance, from the nearest known star, Alpha Centauri, the sun would appear of the average first magnitude, and consequently from that standpoint he might be the gem of some little constellation which had no Sirius, or Arcturus, or Vega to eclipse him with its superior splendor. But from the distance of the vast majority of the stars the sun would probably be invisible to the naked eye, and as seen from nearer systems could only rank as a fifth or sixth magnitude star, unnoticed and unknown except by the star-charting astronomer.