East of Scorpio, where the Milky Way, falling in flakes and sheets of silvery splendor upon the southeastern horizon, spreads abroad like an overflowing river, lies Sagittarius, the “Archer,” often represented in the old pictorial charts as a centaur. The stars Lambda (λ), Delta (δ), and Epsilon (ε) form the bent bow. But modern eyes recognize more easily a dipper, formed by the stars Zeta (ζ), Tau (τ), Sigma (σ), Phi (φ), Lambda (λ), and Mu (μ). But the star-clusters in Sagittarius are more interesting than the separate stars. A little southwest of Mu is the famous cluster 8 M., of which Barnard has made a photograph that is amazing beyond all description. Other clusters are all about in this part of the sky. A good opera-glass or field-glass is almost indispensable for one who would enjoy the glory of this wondrous region. Its riches are almost oppressive in their lavish abundance. Here one can have handfuls of stars for the picking up, like sands of gold from the bed of Pactolus. As the glittering incrustations that cover the roofs and walls of the Mammoth Cave are often compared to the starry heavens, so, reversing the image, Sagittarius is like a stupendous cavern of space all ablaze and aglitter with millions of sparkling gems.
Above Scorpio and Sagittarius are the intertwined constellations of Ophiuchus and Serpens. He who may wish to disentangle them is referred to Astronomy with the Naked Eye. But the outlines can be traced in [Chart VII]. The head of Serpens, like those of Hydra and Draco, is plainly marked by a striking group of stars, in this case resembling the figure called a “quincunx.” From this point just under the “Northern Crown,” the serpent’s stars wind downward in beautiful pairs and groups, crossing the meridian above Scorpio, and rising again in the eastern part of the sky, above the little constellation of Sobieski’s Shield, until they meet the borders of Aquila. Ophiuchus, with his head high up toward Hercules, where it is marked by the brightest star in that part of the sky, Alpha Ophiuchi, or Ras Alhague, the “Head of the Serpent Charmer,” stands with legs braced wide apart, grasping the serpent at the points marked by the stars Delta (δ) and Epsilon (ε), and Tau (τ) and Nu (ν). It is Esculapius with his Serpent, said the Greeks; it is St. Paul and the Viper of Melita, or Moses and the Brazen Serpent, we don’t know which, said the churchmen. I am not aware that in England they have ever been tempted to call it St. George and the Dragon. Politics and national pride have not meddled much with the stars, although there was once an attempt to fix the name of Napoleon upon Orion. Ras Alhague is described by R. H. Allen as sapphire in hue, while Alpha Serpentis is yellowish. The star Lambda (λ) in Ophiuchus, also called Marfik, the “Elbow,” is a beautiful binary, period 235 years, distance apart 1″.2. The smaller star is smalt blue, a splendid telescopic object.
But, as in the case of Sagittarius, the greater wonders here are in the form of star-clusters, and particularly nebulæ. Just above Antares, in one of the feet of Ophiuchus, is a small star, Rho (to find which the reader must consult a large star atlas, like Klein’s), around which Barnard has discovered, by photography, a truly marvellous nebula, a nebula which appears to obscure the stars like a cloud of cosmic dust. Great black lanes extend from and around it, and even the luminous parts of the nebula seem to absorb the light of the stars behind, diminishing their brightness a whole magnitude or more where they are veiled by it. This entire region of sky is most strange to the photographic eye. An outlier of the nebula just mentioned surrounds the star Nu (ν) in Scorpio, and its veiling effect upon the stars is even more evident. There is a similar appearance around the star Theta (θ) Ophiuchi, not far away. The sense of some appalling mystery in this part of the firmament is heightened by what Barnard says of a thing which has reappeared again and again on his photographs during the past fifteen years, at a point which he describes as lying very closely to R. A. xviii hours, 25 m., 31 s.; Decl. S. 26°, 9′ (near the star Lambda (λ) in Sagittarius).
“It is a small, black hole in the sky. It is round and sharply defined. Its measured diameter on the negative is 2′.6. On account of its sharpness and smallness and its isolation, this is perhaps the most remarkable of all the black holes with which I am acquainted. It lies in an ordinary part of the Milky Way, and is not due to the presence or absence of stars, but seems really to be a marking on the sky itself” (Astrophysical Journal, January, 1910).
These things really transcend explanation (see Curiosities of the Sky).
Above Ophiuchus and his Serpent, almost exactly overhead in the latitude of 40° N., we see the quadrilateral figure marked out by four of the principal stars of the constellation Hercules. The head of Draco, described in Chapter I, is beyond it toward the north-northeast. Hercules stands feet upward in the sky, his head, indicated by the star Alpha, or Ras Algethi, the “Kneeler’s Head,” being situated a few degrees west-northwest of Ras Alhague. Thus the two giants have their heads together. But while the occupation of Ophiuchus is plain, nobody, not even in ancient times, when the constellation received its name, has ever been able to say what Hercules is laboring at. When he was on the earth everybody followed his deeds and understood, if they could not emulate, them. He was as comprehensible as a modern pugilist. Now, however, that he has been translated to the stars, his labors are of a more mysterious nature, and, judging from his attitude, he finds them harder than any he undertook for the benefit of mankind here below. One is tempted to think that the powers he offended, when he boldly entered the land of shades and snatched the wife of his friend, King Admetus, from the hand of Death himself, are now taking an ample vengeance.
Ras Algethi is a very beautiful double star, one red, the other green or blue, and both, strangely enough, are variable in brightness. Their distance apart is 4″.7. Their spectrum indicates that they are advanced toward extinction many stages beyond our sun.
The star Zeta (ζ), one of those in the quadrilateral, is a closer double, distance about 1″, and is binary, the period of revolution being about thirty-five years.
And now for a great marvel. Let the eye range slowly from Eta (η) directly toward Zeta (ζ). When one-third of the distance between the two stars has been passed, a faint, glimmering speck will be perceived. Perhaps you will need an opera-glass to make sure that you see it. This is the “Great Cluster in Hercules.” You must go to the southern hemisphere to find its match anywhere in the sky. It is a ball of suns! Now you need a telescope. You must have one. You must either buy or borrow it, or you must pay a visit to an observatory, for this is a thing that no intelligent human being in these days can afford not to see. Can it be possible that any man can know that fifteen thousand suns are to be seen, burning in a compact globular cluster, and not long to regard them with his own eyes? Of what use is description in such a case? The language has not yet been invented to depict such things. Human speech comes down to us from the times when men did not need the tongue of the gods to tell what they saw. When Galileo invented the telescope, and Herschel multiplied its powers a thousandfold, they should have found a language fitted to describe their discoveries. But if you cannot get a look at the Hercules cluster through a powerful telescope, photography comes to your aid. Look at one of the wonderful Lick or Yerkes photographs of it, and pause long on what you see. Note the crowding of those suns toward the centre, note the glittering spiral lines formed by those which seem streaming and hurrying from all sides to join the marvellous congregation—and then turn again to that faint speck in the sky, which is all that the naked eye reveals of the wonder, and reflect upon the meaning of space and the universe.
We now turn farther east, still keeping the eyes directed high in the sky, and just at the edge of the Milky Way, with two minute stars making a little triangle with it, we see Vega or Alpha Lyræ, the astonishing brilliant that flashes on the strings of the heavenly Lyre. At the Vernal Equinox it was just rising far over in the northeast; now it is the unquestioned queen of that quarter of the sky. I like to think of Emerson when looking at that star. There is a sentence of his which reflects it like a mirror. When he strove to rouse the “sluggard intellect of this continent,” to “look from under its iron lids,” he could find no stronger image than that of poetry reviving here and leading in a new age, “as the star in the constellation Harp, which now flames in our zenith, astronomers announce, shall one day be the Pole-star for a thousand years.”