The History Of The Constellations

( Originally Published Early 1900's )

To the grouping of the stars into constellations may well be applied the legal phrase that the custom is so ancient that the memory of man runneth not to the contrary.

The germs of it are evidently to be found in Holy Scripture. The three following passages, which I cite from the Revised Version, whatever else may be said of them, clearly imply that the allusions are to some well-established usage :

" Which maketh the Bear, Orion, and the Pleiades, and the chambers of the south." (Job ix. 9.)

" Canst thou bind the cluster of the Pleiades, or loose the bands of Orion? Canst thou lead forth the Mazzaroth in their season ? Or canst thou guide the Bear with her train?" (Job xxxviii. 31-2.)

" Seek Him that maketh the Pleiades * and Orion." (Amos v. 8.)

The constellations now in use are about 8o or 90 in number, counting a few minor ones devised during the last century, chiefly for the Southern hemisphere, but by no means counting all that have been proposed. It has been well remarked :—" Half a century ago no astronomer seemed comfortable in his position till he had ornamented some little cluster of stars of his own picking with a name of his own making." Of the constellations now recognised, no fewer than 48, and those including with scarcely any exception the largest and best known, are recorded by Ptolemy, and therefore have an unchallenged antiquity of 2000 years, yet the date of the actual invention of even one of them is quite unknown. Seneca attributed the subdivision of the heavens into constellations to the Greeks 1400 years before Christ, but there is no proof of this, and if it is permissible to draw inferences without having many facts to go upon (a common practice nowadays), I should be rather inclined to give some of the credit of inventing the constellations to the Chaldaeans or Egyptians, or to both of them in shares, the Egyptians having developed that which they derived from the Chaldans, as the Chaldaeans may have developed something they derived from peoples which preceded them. Some writers, indeed, have thought that a much greater antiquity should be as-signed to the constellations, and there are not wanting traces of proof to support this idea. Neglecting for the moment the ancient constellations as a whole, it certainly seems clear that a special degree of antiquity attaches to the signs of the zodiac, and no wonder, seeing that they remind us, amongst other things, of the apparent annual path of the sun amongst the stars.

It seems more than probable almost certain that the word " Mazzaroth " quoted above from Job xxxviii. 32, and left untranslated in the text by the authors of the Revised Version, means what they have suggested in the margin, namely, the circle of the zodiac. And it is quite consistent with this to find, as a modern writer has pointed out, that :—" These signs were known among all nations and in all ages. From the almost antediluvian chronologies of China, India, and Egypt, to the traditions of the recently discovered islands of the South Sea, traces of them are discovered most clearly among the most ancient and earliest civilised nations. In the remains of Assyria they are recognised ; in those of Egypt they are perfectly preserved ; in those of Etruria and Mexico they are trace-able. This wide diffusion indicates a common origin, both of the race of man and of the symbols of astronomy. The love of symbols has been considered as natural to man ; the creation amid which he is placed is symbolical. Of this universal tendency the inventors of astronony seem to have availed themselves, rendering it subservient to man's spiritual education by familiarising to his mind the lofty truths of Divine revelation."

"The earliest positive evidence of the primeval existence of the signs is in the Chinese Annals, where it is said that the Emperor Yao, 2357 years before the Christian era, divided the 12 signs of the zodiac by the 28 mansions of the moon ; but it is not said that he invented them. The Chinese national emblem of the dragon appears to be the dragon of the sphere, which was at that time the polar constellation, the brightest star in the dragon's head having been the Pole Star in the antediluvian ages. The Egyptians, on whose early monuments the signs are found, acknowledged that they derived their astronomy from the Chaldaeans. The Chaldaeans attributed their science to Oannes, supposed to be Noah. The Arabs and Brahmins, among whom astronomy was early cultivated, seem to have derived it from Abraham, through Ishmael, and the children of Keturah. The Greeks sup-posed their imperfect knowledge of the subject came through the Egyptians and Chaldaeans. The Romans are thought to have received through the Etrurians the names of the signs still in use among European nations. The Etrurians are considered to have derived them, with their other arts and sciences, from Assyria. The early Greek poet Hesiod is said to have made use of Assyrian records. He mentions some of the constellations by the names they now bear. Cleostratus [circa 500 B. C.] was acquainted with the signs, and wrote on Aries and Sagittarius. A later Greek poet, Aratus, described the constellations such as we now have them, and by equivalent names. He gave neither history nor conjecture as to their date, their meaning, or their origin. They were to him, as to us, of immemorial antiquity."

The thoughts unfolded in the foregoing extract are of great interest, but it is obvious that a thorough investigation of this subject would lead us far beyond the limits of this little volume.

To say much that is definite about the number of the stars is in one sense a very difficult thing to do if the idea is to furnish any trust-worthy or adequate information on the subject. The words of Holy Scripture, " Look now towards heaven, and tell the stars, if thou be able to number them," cover much more than appears at first sight. To say that the stars are innumerable is far from being a mere poetic phrase ; it is in-deed no more than a prosaic matter of fact. Nevertheless it may probably surprise some persons to be told that according to the estimate of the distinguished German astronomer Argelander the number of stars visible to the naked eye in the latitude of Berlin is only 3256, and must be put no higher than about 5000 in all for the whole heavens. The number to be seen becomes greater as we approach the equator from the middle latitudes of either hemisphere, owing to the wider expanse opened up to an observer stationed at the equator. An observer located in a place the latitude of which is o° will see in the course of the year all the naked-eye stars in the heavens.

Argelander's totals arranged in magnitudes are as follows :

Stars.

1st magnitude = 20
2nd = 65
3rd = 190
4th = 425
5th = 100
6th = 3,200
7th = 13,000
8th = 40,000
9th = 142,000

This matter has been made the subject of estimate by various observers, including especially the late Professor Grant of Glasgow and Karl Von Littrow of Vienna. Their figures, though fairly accordant as regards naked-eye stars in the aggregate, differ a good deal, magnitude by magnitude, owing to there being no recognised defined standards of magnitude.

As to this, however, it may be remarked as a thing by the way, that Seidel, a German observer who has given much attention to the matter, has suggested the following as standard stars for the first 4 magnitudes : -

1st—a Aquilae, a Virginis, a Orionis.

2nd—a Ursea Majoris, y Cassiopeim, Algol (at max.).

3rd—y Lyrae, S Herculis, O Aquilea.

4th_ p Herculis, x Draconis (too bright), Boötis, 0 Herculis (too faint).

It may be well to point out that the statistics just given, though necessarily somewhat approximate, are not to be regarded as imaginary, though of course to count a number of points of light like stars is not in itself an easy task. It may be worth while, therefore, to carry the foregoing statements a little farther. A very painstaking astronomer, also a German, Heis of Münster, affirmed that it was not possible to count more than about 5000 stars visible in the sky available in Central Europe. Endowed with a sharp sight, and adopting various artifices (such as shutting out all artificial light and marking off by means of a great black tube each region of the sky under examination), he found himself able at Münster to see 5421 stars. Inasmuch as he could from that one place in the course of a year examine in succession 8/10ths of the heavens, he concluded that supposing the portion of the Southern hemisphere which he could not see resembled in a sense the rest of the sky which he could see, the sum total of the stars visible to the naked eye would mount up to about 6800. But it deserves notice that no possible number of stars which could be counted would represent the stars which an eye could discern. The eye can take notice of more than it can count, because when any given star imprints itself upon the centre of the retina, others whose images fall upon the corners of the eye, so to speak, seem to vanish. This is a point as to which appearances are apt to be very deceptive. It may be well here to remark that it is important to distinguish clearly in the mind between the results of a single gaze at the sky, the eye being for the while fixed, and a look all round. In the former case it may be taken that no more than a space of 13° or 14° can be taken in simultaneously, whilst by moving the eye methodically in successive directions the whole expanse of the heavens may be brought under review.

Secchi noted the following experiment as one that he often tried with interesting results. After taking a glance at some particular part of the heavens he would transfer his eye to the finder of the great telescope at the Roman College at Rome, and would see in this subordinate telescope, whose field was no larger than °, as many stars as were to be seen in the 13° or 14° grasped by the naked eye. Passing then to his great telescope, armed with an eye-piece showing only an arc of 15', or one-fourth the area of the field of his finder, he would still see as many stars as in the finder ; proceeding yet further to diminish the field by increasing the power, the number of the stars would scarcely diminish, because, though the area was curtailed, yet the increased magnifying power revealed minute stars which had previously escaped notice. Thus it came about that in certain localitiesit was possible to see in a field no more than 1/12° in diameter as many stars as were visible to the naked eye in a field 13° in diameter. This train of thought will readily enable the general reader to realise the fact that the larger our telescopes become the more stars we can discern ; in other words, that as we cannot say for a certainty how large our telescopes might become, so accordingly we cannot say when stars hitherto unseen will cease to be invisible by becoming visible. So that we may indeed say with Galileo that the stars are innumerable.

The heavens are not everywhere equally rich ; in many places even with the largest instruments one can find in a field of scarcely 5 or 6 stars : it would not, therefore, do to judge of the number of the stars by these exceptional regions. An effort was made by the two Herschels, Sir William in the Northern hemisphere, and Sir John in the Southern hemisphere, to ascertain the possible number of the stars. It is easy to understand that this is one of the most gigantic tasks which an astronomer could undertake, because it could never be completed in the lifetime of one man. Sir W. Herschel adopted an indirect method to arrive at his results. Making use of his 20-ft. reflector, he directed it successively towards certain parts of the heavens, chosen in irregular order, of which he noted the right ascension and declination. These regions were so distributed over the heavens as in a way to result in the sky being dotted over with a network of surveying stations equidistant from each other. The field of his telescope was just 1/4°, and the magnifying power 120. He counted in each field the number of stars visible in it ; in particular places where the number was so great as to render counting impossible he made an estimate. Having gathered together a certain number of these counts, or estimates, in a particular part of the sky, he summed up the total number of stars seen, and divided this total by the number of the groups. The resulting figure was taken to represent the mean average density of the stars in the neighbourhood of the place examined. This method, the only one possible in practice, has some defects ; still, employed on the large scale carried out by Sir William Herschel, it gave results so far conclusive that no more modern effort has yet superseded it. Of course it will often happen that a certain locality will be very rich in stars, whilst in another like area, not far off, there will be a great scarcity of stars ; still, taking rich and poor neighbourhoods together, a fairly trustworthy average result will be obtained. It has already been stated that to take a census of the whole heavens would be a work so vast that no one man could ever hope to accomplish it ; there is, however, now in progress an international photo-graphic survey of the heavens, which, when it is complete, will go far to fill up the void in our knowledge which at present exists ; but before speaking of this it will be bet ter to finish with the work of the Herschels in this department of astronomy. To obtain an idea of it, it will suffice to remember that Sir W. Herschel dealt with 3400 groups. These were not all completely independent of one another, and they must be reduced to the smaller number of 683 in order to obtain the number of the quite independent groups. Herschel is considered to have examined only both part of the sky ; it would have taken him 83 years to have gone over the entire heavens, allowing that he could have done too fields every night, and could have found too favourable nights in every year. In some regions the stars were so numerous that Sir William counted 588 in one field of view, and, the telescope remaining stationary, field after field quite as rich passed along as in a panorama for several minutes. At one place he estimated that he had seen 116,000 stars passing before him in a quarter of an hour ; and that on another occasion 258,000 stars passed in 41 minutes ; on the other hand, in other parts of the heavens fields presented themselves with only two or three stars in them. The results which Sir W. Herschel arrived at were published in 1785. Nearly 50 years later his son, who went out to the Cape of Good Hope for the express purpose of carrying on observations in the Southern hemisphere, took up again this very self-same question of the numbering of the stars. His results, equally as interesting as his father's, differed from them in this particular, that the Southern hemisphere is less uniformly decked with stars than the Northern hemisphere, and bare places are more common.

By a computation based on the results of gauging both hemispheres, Sir John Herschel found that the total number of stars visible in an 18-inch reflector cannot be less than 51 millions, but Struve, interpreting Sir W. Herschel's observations in the light of his own, estimated that more than 20 millions of stars were within the grasp of a reflector of the named dimensions.

The most cursory examination of the heavens will make it clear that the stars are very unequally distributed that in some parts they are very much more closely arranged than in others, and that this is true whether we consider their absolute number or their individual brightness. Various attempts have been made to frame speculations as to the causes and meaning of these facts, but it is obvious that all such speculations must be more or less useless and unprofitable. I may have something more to say on this subject when we come to deal with that wonderful mass of stars which we call the Galaxy, or Milky Way, but an investigation as to the " how " or the " why " there are more stars to be seen in some places than in others would, in the present state of our knowledge, lead to no very definite or satisfactory results.

A few words about the International Photographic Survey of the Heavens which is now in progress. This took its origin from a Conference of Astronomers, representing 16 different nationalities, which met at the Paris Observatory in April, 1887, on the invitation of the Academy of Sciences of France. The basis on which the undertaking was started was in substance defined as follows : (1) That the progress made in astronomical photography demands that the astronomers of the present day should unite in obtaining a permanent record of the heavens by means of photography. (2) That the work should be carried out at selected stations, and with instruments which should be identical in size and other essential features. (3) That the principal object to be aimed at is to secure a chart of the heavens for the present epoch, and therewith data for determining with the greatest possible accuracy the positions and brightness of all stars down to a given magnitude, the ultimate idea being that the information thus obtained should be so preserved as to be available in future years for determining whether changes of position or brightness have occurred in respect of any given stars. These preliminary principles having been accepted by the Conference, which comprised 20 representatives for France, 8 for England and the British Colonies, 6 for Germany, 3 each for Russia, Holland, and the United States, 2 each for Austria, Sweden, and Denmark, and I each for Belgium, Italy, Spain, Portugal, Switzerland, Brazil, and Argentina, a committee was appointed to consider and report upon the form and size of the instruments to be used and the range of magnitudes to be embraced. After a large amount of anxious inquiry and debate, it was eventually decided that the instruments employed should be exclusively refractors of 11 inches aperture, and rather more than 11 feet focal length, giving a field of 2° square, the photographic plates being 6i inches square, and showing an effective square (réseau) of 5 1/8 inches, with lines inch apart.

The necessary instruments have been provided, chiefly at the cost of the Governments of the respective countries, and the survey is now well in hand at the following 19 observatories Helsingfors, Potsdam, Oxford, Greenwich, Paris, Vienna, Bordeaux, Toulouse, Catane, Algiers, San Fernando, Chapultepec, Tacubaya, Rio de Janeiro, Santiago, Sydney, Cape of Good Hope, La Plata, and Mel-bourne. These observatories range in latitude from 6o° N. to 38° S., and may be considered as conveniently placed for embracing the whole sky. It is scarcely necessary to add that the work undertaken is one of enormous magnitude, and, though not actually difficult, requires in a high degree the services of observers well endowed with the virtues of patience and carefulness. The work will, of course, occupy several years.