Curiosities of the Sky - Garrett P. Serviss (best book clubs txt) 📗

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 ({beta}), Alpha ({alpha}), Gamma ({gamma}), Delta ({delta}), and Epsilon ({epsilon}). 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 six degrees — 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.

 

Conflagrations in the Heavens

 

Suppose it were possible for the world to take fire and burn up — as some pessimists think that it will do when the Divine wrath shall have sufficiently accumulated against it — nobody out of our own little corner of space would ever be aware of the catastrophe! With all their telescopes, the astronomers living in the golden light of Arcturus or the diamond blaze of Canopus would be unable to detect the least glimmer of the conflagration that had destroyed the seat of Adam and his descendents, just as now they are totally ignorant of its existence.

 

But at least fifteen times in the course of recorded history men looking out from the earth have beheld in the remote depths of space great outbursts of fiery light, some of them more splendidly luminous than anything else in the firmament except the sun! If they were conflagrations, how many million worlds like ours were required to feed their blaze?

 

It is probable that “temporary” or “new” stars, as these wonderful apparitions are called, really are conflagrations; not in the sense of a bonfire or a burning house or city, but in that of a sudden eruption of inconceivable heat and light, such as would result from the stripping off the shell of an encrusted sun or the crashing together of two mighty orbs flying through space with a hundred times the velocity of the swiftest cannon-shot.

 

Temporary stars are the rarest and most erratic of astronomical phenomena. The earliest records relating to them are not very clear, and we cannot in every instance be certain that it was one of these appearances that the ignorant and superstitious old chroniclers are trying to describe. The first temporary star that we are absolutely sure of appeared in 1572, and is known as “Tycho’s Star,” because the celebrated Danish astronomer (whose remains, with his gold-and-silver artificial nose — made necessary by a duel — still intact, were disinterred and reburied in 1901) was