Astronomy with an Opera-glass Part 2

Sweep along the whole length of the Dipper's handle, and you will discover many fine fields of stars. Then look at the star Alpha ([alpha]) in the outer edge of the bowl nearest to the pole-star. There is a faint star, of about the eighth magnitude, near it, in the direction of Beta ([beta]). This will prove a very difficult test. You will have to try it with averted vision. If you have a field-gla.s.s, catch it first with that, and, having thus fixed its position in your mind, try to find it with the opera-gla.s.s. Its distance is a little over half that between Mizar and Alcor. It is of a reddish color.

You will notice nearly overhead three pairs of pretty bright stars in a long, bending row, about half-way between Leo and the Dipper. These mark three of Ursa Major's feet, and each of the pairs is well worth looking at with a gla.s.s, as they are beautifully grouped with stars invisible to the naked eye. The letters used to designate the stars forming these pairs will be found upon our map of Ursa Major. The scattered group of faint stars beyond the bowl of the Dipper forms the Bear's head, and you will find that also a field worth a few minutes' exploration.

[Ill.u.s.tration: MIZAR, ALCOR, AND THE SIDUS LUDOVICIANUM.]

The two bears, Ursa Major and Ursa Minor, swinging around the pole of the heavens, have been conspicuous in the star-lore of all ages.

According to fable, they represent the nymph Calisto, with whom Jupiter was in love, and her son Arcas, who were both turned into bears by Juno, whereupon Jupiter, being unable to restore their form, did the next best thing he could by placing them among the stars. Ursa Major is Calisto, or Helica, as the Greeks called the constellation. The Greek name of Ursa Minor was Cynosura. The use of the pole-star in navigation dates back at least to the time of the Phoenicians. The observer will note the uncomfortable position of Ursa Minor, attached to the pole by the end of its long tail.

But, after all, no one can expect to derive from such studies as these any genuine pleasure or satisfaction unless he is mindful of the real meaning of what he sees. The actual truth seems almost too stupendous for belief. The mind must be brought into an att.i.tude of profound contemplation in order to appreciate it. From this globe we can look out in every direction into the open and boundless universe. Blinded and dazzled during the day by the blaze of that star, of which the earth is a near and humble dependent, we are shut in as by a curtain. But at night, when our own star is hidden, our vision ranges into the depths of creation, and we behold them sparkling with a mult.i.tude of other suns.

With so simple an aid as that of an opera-gla.s.s we penetrate still deeper into the profundities of s.p.a.ce, and thousands more of these strange, far-away suns come into sight. They are arranged in pairs, sets, rows, streams, cl.u.s.ters--here they gleam alone in distant splendor, there they glow and flash in mighty swarms. This is a look into heaven more splendid than the imagination of Bunyan pictured; here is a celestial city whose temples are suns, and whose streets are the pathways of light.

CHAPTER II.

THE STARS OF SUMMER.

Let us now suppose that the Earth has advanced for three months in its...o...b..t since we studied the stars of spring, and that, in consequence, the heavens have made one quarter of an apparent revolution. Then we shall find that the stars which in spring shone above the western horizon have been carried down out of sight, while the constellations that were then in the east have now climbed to the zenith, or pa.s.sed over to the west, and a fresh set of stars has taken their place in the east. In the present chapter we shall deal with what may be called the stars of summer; and, in order to furnish occupation for the observer with an opera-gla.s.s throughout the summer months, I have endeavored to so choose the constellations in which our explorations will be made, that some of them shall be favorably situated in each of the months of June, July, and August. The circular map represents the heavens at midnight on the 1st of June; at eleven o'clock, on the 15th of June; at ten o'clock, on the 1st of July; at nine o'clock, on the 15th of July; and at eight o'clock, on the 1st of August. Remembering that the center of the map is the point over his head, and that the edge of it represents the circle of the horizon, the reader, by a little attention and comparison with the sky, will be able to fix in his mind the relative situation of the various constellations. The maps that follow will show him these constellations on a larger scale, and give him the names of their chief stars.

[Ill.u.s.tration: MAP 7.]

The observer need not wait until midnight on the 1st of June in order to find some of the constellations included in our map. Earlier in the evening, at about that date, say at nine o'clock, he will be able to see many of these constellations, but he must look for them farther toward the east than they are represented in the map. The bright stars in Bootes and Virgo, for instance, instead of being over in the southwest, as in the map, will be near the meridian; while Lyra, instead of shining high overhead, will be found climbing up out of the northeast. It would be well to begin at nine o'clock, about the 1st of June, and watch the motions of the heavens for two or three hours. At the commencement of the observations you will find the stars in Bootes, Virgo, and Lyra in the positions I have just mentioned, while half-way down the western sky will be seen the Sickle of Leo. The brilliant Procyon and Capella will be found almost ready to set in the west and northwest, respectively.

Between Procyon and Capella, and higher above the horizon, shine the twin stars in Gemini.

In an hour Procyon, Capella, and the Twins will be setting, and Spica will be well past the meridian. In another hour the observer will perceive that the constellations are approaching the places given to them in our map, and at midnight he will find them all in their a.s.signed positions. A single evening spent in observations of this sort will teach him more about the places of the stars than he could learn from a dozen books.

Taking, now, the largest opera-gla.s.s you can get (I have before said that the diameter of the object-gla.s.ses should not be less than 1.5 inch, and, I may add, the larger they are the better), find the constellation Scorpio, and its chief star Antares. The map shows you where to look for it at midnight on the 1st of June. If you prefer to begin at nine o'clock at that date, then, instead of looking directly in the south for Scorpio, you must expect to see it just rising in the southeast. You will recognize Antares by its fiery color, as well as by the striking arrangement of its surrounding stars. There are few constellations which bear so close a resemblance to the objects they are named after as Scorpio. It does not require a very violent exercise of the imagination to see in this long, winding trail of stars a gigantic scorpion, with its head to the west, and flourishing its upraised sting that glitters with a pair of twin stars, as if ready to strike. Readers of the old story of Phaeton's disastrous attempt to drive the chariot of the Sun for a day will remember it was the sight of this threatening monster that so terrified the ambitious youth as he dashed along the Zodiac, that he lost control of Apollo's horses, and came near burning the earth up by running the Sun into it.

Antares rather gains in redness when viewed with a gla.s.s. Its color is very remarkable, and it is a curious circ.u.mstance that with powerful telescopes a small, bright-green star is seen apparently almost touching it. Antares belongs to Secchi's third type of suns, that in which the spectroscopic appearances suggest the existence of a powerfully absorptive atmosphere, and which are believed on various grounds to be, as Lockyer has said, "in the last visible stage of cooling"; in other words, almost extinct. This great, red star probably in actual size exceeds our sun, and no one can help feeling the sublime nature of those studies which give us reason to think that here we can actually behold almost the expiring throes of a giant brother of our giant sun. Only, the lifetime of a sun is many millions of years, and its gradual extinction, even after it has reached a stage as advanced as that of Antares is supposed to be, may occupy a longer time than the whole duration of the human race.

A little close inspection with the naked eye will show three fifth- or sixth-magnitude stars above Antares and Sigma ([sigma]), which form, with those stars, the figure of an irregular pentagon. An opera-gla.s.s shows this figure very plainly. The nearest of these stars to Antares, the one directly above it, is known by the number 22, and belongs to Scorpio, while the farthest away, which marks the northernmost corner of the pentagon, is Rho in Ophiuchus. Try a powerful field-gla.s.s upon the two stars just named. Take 22 first. You will without much difficulty perceive that it has a little star under its wing, below and to the right, and more than twice as far away above it there is another faint star. Then turn to Rho. Look sharp and you will catch sight of two companion stars, one close to Rho on the right and a little below, and the other still closer and directly above Rho. The latter is quite difficult to be seen distinctly, but the sight is a very pretty one.

The opera-gla.s.s will show a number of faint stars scattered around Antares. Turn now to Beta ([beta]) in Scorpio, with the gla.s.s. A very pretty pair of stars will be seen hanging below [beta]. Sweeping downward from this point to the horizon you will find many beautiful star-fields. The star marked Nu ([nu]) is a double which you will be able to separate with a powerful field-gla.s.s, the distance between its components being 40".

[Ill.u.s.tration: MAP 8.]

And next let us look at a star-cl.u.s.ter. You will see on Map No. 8 an object marked 4 M, near Antares. Its designation means that it is No. 4 in Messier's catalogue of nebulae. It is not a true nebula, but a closely compacted cl.u.s.ter of stars. With the opera-gla.s.s, if you are looking in a clear and moonless night, you will see it as a curious nebulous speck.

With a field-gla.s.s its real nature is more apparent, and it is seen to blaze brighter toward the center. It is, in fact, one of those universes within the universe where thousands of suns are a.s.sociated together by some unknown law of aggregation into a.s.semblages of whose splendor the slight view that we can get gives us but the faintest conception.

The object above and to the right of Antares, marked in the map 80 M., is a nebula, and although the nebula itself is too small to be seen with an opera-gla.s.s (a field-gla.s.s shows it as a mere wisp of light), yet there is a pretty array of small stars in its neighborhood worth looking at. Besides, this nebula is of special interest, because in 1860 a star suddenly took its place. At least, that is what seemed to have happened.

What really did occur, probably, was that a variable or temporary star, situated between us and the nebula, and ordinarily too faint to be perceived, received a sudden and enormous accession of light, and blazed up so brightly as to blot out of sight the faint nebula behind it. If this star should make its appearance again, it could easily be seen with an opera-gla.s.s, and so it will not be useless for the reader to know where to look for it. The quarter of the heavens with which we are now dealing is famous for these celestial conflagrations, if so they may be called. The first temporary star of which there is any record appeared in the constellation of the Scorpion, near the head, 134 years before Christ. It must have been a most extraordinary phenomenon, for it attracted attention all over the world, and both Greek and Chinese annals contain descriptions of it. In 393 A. D. a temporary star shone out in the tail of Scorpio. In 827 A. D. Arabian astronomers, under the Caliph Al-Mamoun, the son of Haroun-al-Raschid, who broke into the great pyramid, observed a temporary star, that shone for four months in the constellation of the Scorpion. In 1203 there was a temporary star, of a bluish color, in the tail of Scorpio, and in 1578 another in the head of the constellation. Besides these there are records of the appearance of four temporary stars in the neighboring constellation of Ophiuchus, one of which, that of 1604, is very famous, and will be described later on.

It is conceivable that these strange outbursts in and near Scorpio may have had some effect in causing this constellation to be regarded by the ancients as malign in its influence.

We shall presently see some examples of star-cl.u.s.ters and nebulae with which the instruments we are using are better capable of dealing than with the one described above. In the mean time, let us follow the bending row of stars from Antares toward the south and east. When you reach the star Mu ([mu]), you are not unlikely to stop with an exclamation of admiration, for the gla.s.s will separate it into two stars that, shining side by side, seem trying to rival each other in brightness. But the next star below [mu], marked Zeta ([zeta]), is even more beautiful. It also separates into two stars, one being reddish and the other bluish in color. The contrast in a clear night is very pleasing. But this is not all. Above the two stars you will notice a curious nebulous speck. Now, if you have a powerful field-gla.s.s, here is an opportunity to view one of the prettiest sights in the heavens. The field-gla.s.s not only makes the two stars appear brighter, and their colors more p.r.o.nounced, but it shows a third, fainter star below them, making a small triangle, and brings other still fainter stars into sight, while the nebulous speck above turns into a charmingly beautiful little star-cl.u.s.ter, whose components are so close that their rays are inextricably mingled in a maze of light. This little cut is an attempt to represent the scene, but no engraving can reproduce the life and sparkle of it.

[Ill.u.s.tration: ZETA SCORPIONIS.]

Following the bend of the Scorpion's tail upward, we come to the pair of stars in the sting. These, of course, are thrown wide apart by the opera-gla.s.s. Then let us sweep off to the eastward a little way and find the cl.u.s.ter known as 7 M. You will see it marked on the map. Above it, and near enough to be included in the same field of view, is 6 M., a smaller cl.u.s.ter. Both of these have a sparkling appearance with an opera-gla.s.s, and by close attention some of the separate stars in 7 M.

may be detected. With a field-gla.s.s these cl.u.s.ters become much more striking and starry looking, and the curious radiated structure of 7 M.

comes out.

In looking at such objects we can not too often recall to our minds the significance of what we see--that these glimmering specks are the lights in the windows of the universe which carry to us, across inconceivable tracts of s.p.a.ce, the a.s.surance that we and our little system are not alone in the heavens; that all around us, and even on the very confines of immensity, Nature is busy, as she is here, and the laws of light, heat, gravitation (and why not of life?), are in full activity.

The cl.u.s.ters we have just been looking at lie on the borders of Scorpio and Sagittarius. Let us cross over into the latter constellation, which commemorates the centaur Chiron. We are now in another, and even a richer, region of wonders. The Milky-Way, streaming down out of the northeast, pours, in a luminous flood, through Sagittarius, inundating that whole region of the heavens with seeming deeps and shallows, and finally bursting the barriers of the horizon disappears, only to glow with redoubled splendor in the southern hemisphere. The stars Zeta ([zeta]), Tau ([tau]), Sigma ([sigma]), Phi ([phi]), Lambda ([lambda]), and Mu ([mu]) indicate the outlines of a figure sometimes called the Milk-Dipper, which is very evident when the eye has once recognized it.

On either side of the upturned handle of this dipper-like figure lie some of the most interesting objects in the sky. Let us take the star [mu] for a starting-point. Sweep downward and to the right a little way, and you will be startled by a most singular phenomenon that has suddenly made its appearance in the field of view of your gla.s.s. You may, perhaps, be tempted to congratulate yourself on having got ahead of all the astronomers, and discovered a comet. It is really a combination of a star-cl.u.s.ter with a nebula, and is known as 8 M. Sir John Herschel has described the "nebulous folds and ma.s.ses" and dark oval gaps which he saw in this nebula with his large telescope at the Cape of Good Hope.

But no telescope is needed to make it appear a wonderful object; an opera-gla.s.s suffices for that, and a field-gla.s.s reveals still more of its marvelous structure.

The reader will recollect that we found the summer solstice close to a wonderful star-swarm in the feet of Gemini. Singularly enough the winter solstice is also near a star-cl.u.s.ter. It is to be found near a line drawn from 8 M. to the star [mu] Sagittarii, and about one third of the way from the cl.u.s.ter to the star. There is another less conspicuous star-cl.u.s.ter still closer to the solst.i.tial point here, for this part of the heavens teems with such aggregations.

On the opposite side of the star [mu]--that is to say, above and a little to the left--is an entirely different but almost equally attractive spectacle, the swarm of stars called 24 M. Here, again, the field-gla.s.s easily shows its superiority over the opera-gla.s.s, for magnifying power is needed to bring out the innumerable little twinklers of which the cl.u.s.ter is composed. But, whether you use an opera-gla.s.s or a field-gla.s.s, do not fail to gaze long and steadily at this island of stars, for much of its beauty becomes evident only after the eye has accustomed itself to disentangle the glimmering rays with which the whole field of view is filled. Try the method of averted vision, and hundreds of the finest conceivable points of light will seem to spring into view out of the depths of the sky. The necessity of a perfectly clear night, and the absence of moonlight, can not be too much insisted upon for observations such as these. Everybody knows how the moonlight blots out the smaller stars. A slight haziness, or smoke, in the air produces a similar effect. It is as important to the observer with an opera-gla.s.s to have a transparent atmosphere as it is to one who would use a telescope; but, fortunately, the work of the former is not so much interfered with by currents of air. Always avoid the neighborhood of any bright light. Electric lights in particular are an abomination to star-gazers.

The cloud of stars we have just been looking at is in a very rich region of the Milky-Way, in the little modern constellation called "Sobieski's Shield," which we have not named upon our map. Sweeping slowly upward from 24 M. a little way with the field-gla.s.s, we will pa.s.s in succession over three nebulous-looking spots. The second of these, counting upward, is the famous Horseshoe nebula. Its wonders are beyond the reach of our instrument, but its place may be recognized. Look carefully all around this region, and you will perceive that the old G.o.ds, who traveled this road (the Milky-Way was sometimes called the pathway of the G.o.ds), trod upon golden sands. Off a little way to the east you will find the rich cl.u.s.ter called 25 M. But do not imagine the thousands of stars that your opera-gla.s.s or field-gla.s.s reveals comprise all the riches of this Golconda of the heavens. You might ply the powers of the greatest telescope in a vain attempt to exhaust its wealth. As a hint of the wonders that lie hidden here, let me quote Father Secchi's description of a starry spot in this same neighborhood, viewed with the great telescope at Rome. After telling of "beds of stars superposed upon one another," and of the wonderful geometrical arrangement of the larger stars visible in the field, he adds:

"The greater number are arranged in spiral arcs, in which one can count as many as ten or twelve stars of the ninth to the tenth magnitude following one another in a curve, like beads upon a string. Sometimes they form rays which seem to diverge from a common focus, and, what is very singular, one usually finds, either at the center of the rays, or at the beginning of the curve, a more brilliant star of a red color, which seems to lead the march. It is impossible to believe that such an arrangement can be accidental."

The reader will recall the somewhat similar description that Admiral Smyth and Mr. Webb have given of a star-cl.u.s.ter in Gemini (see Chapter I).

The milky look of the background of the Galaxy is, of course, caused by the intermingled radiations of inconceivably minute and inconceivably numerous stars, thousands of which become separately visible, the number thus distinguishable varying with the size of the instrument. But the most powerful telescope yet placed in human hands can not sound these starry deeps to the bottom. The evidence given by Prof. Holden, the Director of the Lick Observatory, on this point is very interesting.

Speaking of the performance of the gigantic telescope on Mount Hamilton, thirty-six inches in aperture, he says:

"The Milky-Way is a wonderful sight, and I have been much interested to see that there is, even with our superlative power, no final resolution of its finer parts into stars. There is always the background of unresolved nebulosity on which hundreds and thousands of stars are studded--each a bright, sharp, separate point."

The groups of stars forming the eastern half of the constellation of Sagittarius are worth sweeping over with the gla.s.s, as a number of pretty pairs may be found there.

Sagittarius stands in the old star-maps as a centaur, half-horse-half-man, facing the west, with drawn bow, and arrow pointed at the Scorpion.

[Ill.u.s.tration: MAP 9.]

Next let us pa.s.s to the double constellation adjoining Scorpio and Sagittarius on the north--Ophiuchus and the Serpent. These constellations, as our map shows, are curiously intermixed. The imagination of the old star-gazers, who named them, saw here the figure of a giant grasping a writhing serpent with his hands. The head of the serpent is under the Northern Crown, and its tail ends over the star-gemmed region that we have just described, called "Sobieski's Shield." Ophiuchus stands, as figured in Flamsteed's "Atlas," upon the back of the Scorpion, holding the serpent with one hand below the neck, this hand being indicated by the pair of stars marked Epsilon ([epsilon]) and Delta ([delta]), and with the other near the tail. The stars Tau ([tau]) and Nu ([nu]) indicate the second hand. The giant's face is toward the observer, and the star Alpha ([alpha]), also called Ras Alhague, shines in his forehead, while Beta ([beta]) and Gamma ([gamma]) mark his right shoulder. Ophiuchus has been held to represent the famous physician aesculapius. One may well repress the tendency to smile at these fanciful legends when he reflects upon their antiquity.

There is no doubt that this double constellation is at least three thousand years old--that is to say, for thirty centuries the imagination of men has continued to shape these stars into the figures of a gigantic man struggling with a huge serpent. If it possesses no other interest, then it at least has that which attaches to all things ancient. Like many other of the constellations it has proved longer-lived than the mightiest nations. While Greece flourished and decayed, while Rome rose and fell, while the scepter of civilization has pa.s.sed from race to race, these starry creations of fancy have shone on unchanged. The mind that would ignore them now deserves compa.s.sion.

The reader will observe a little circle in the map, and near it the figures 1604. This indicates the spot where one of the most famous temporary stars on record appeared in the year 1604. At first it was far brighter than any other star in the heavens; but it quickly faded, and in a little over a year disappeared. It is particularly interesting, because Kepler--the quaintest, and not far from the greatest, figure in astronomical history--wrote a curious book about it. Some of the philosophers of the day argued that the sudden outburst of the wonderful star was caused by the chance meeting of atoms. Kepler's reply was characteristic, as well as amusing:

"I will tell those disputants, my opponents, not my own opinion, but my wife's. Yesterday, when I was weary with writing, my mind being quite dusty with considering these atoms, I was called to supper, and a salad I had asked for was set before me. 'It seems, then,' said I, aloud, 'that if pewter dishes, leaves of lettuce, grains of salt, drops of water, vinegar and oil, and slices of egg, had been flying about in the air from all eternity, it might at last happen by chance that there would come a salad.' 'Yes,' says my wife, 'but not so nice and well-dressed as this of mine is.'"

While there are no objects of special interest for the observer with an opera-gla.s.s in Ophiuchus, he will find it worth while to sweep over it for what he may pick up, and, in particular, he should look at the group of stars southeast of [beta] and [gamma]. These stars have been shaped into a little modern asterism called Taurus Poniatowskii, and it will be noticed that five of them mark the outlines of a letter V, resembling the well-known figure of the Hyades.

Also look at the stars in the head of Serpens, several of which form a figure like a letter [X]. A little west of Theta ([theta]) in the tail of Serpens, is a beautiful swarm of little stars, upon which a field-gla.s.s may be used with advantage. The star [theta] is itself a charming double, just within the separating power of a very powerful field-gla.s.s under favorable circ.u.mstances, the component stars being only about one third of a minute apart.

Do not fail to notice the remarkable subdivisions of the Milky-Way in this neighborhood. Its current seems divided into numerous channels and bays, interspersed with gaps that might be likened to islands, and the star [theta] appears to be situated upon one of these islands of the galaxy. This complicated structure of the Milky-Way extends downward to the horizon, and upward through the constellation Cygnus, and of its phenomenal appearance in that region we shall have more to say further on.

Directly north of Ophiuchus is the constellation Hercules, interesting as occupying that part of the heavens toward which the proper motion of the sun is bearing the earth and its fellow-planets, at the rate, probably, of not less than 160,000,000 miles in a year--a stupendous voyage through s.p.a.ce, of whose destination we are as ignorant as the crew of a ship sailing under sealed orders, and, like whom, we must depend upon such inferences as we can draw from courses and distances, for no other information comes to us from the flagship of our squadron.

[Ill.u.s.tration: MAP 10.]

In the accompanying map we have represented the beautiful constellations Lyra and the Northern Crown, lying on either side of Hercules. The reader should note that the point overhead in this map is not far from the star Eta ([eta]) in Hercules. The bottom of the map is toward the south, the right-hand side is west, and the left-hand side east. It is important to keep these directions in mind, in comparing the map with the sky. For instance, the observer must not expect to look into the south and see Hercules half-way up the sky, with Lyra a little east of it; he must look for Hercules nearly overhead, and Lyra a little east of the zenith. The same precautions are not necessary in using the maps of Scorpio, Sagittarius, and Ophiuchus, because those constellations are nearer the horizon, and so the observer does not have to imagine the map as being suspended over his head.