The wonder and the glory of the stars

Front matter

Sa a ea ae ee ene

Ses are eto

Se Se = ea hp St ato

Preface

Tuis volume of astronomical sketches is the outcome of nearly two hundred distinct lectures delivered during the last twenty-two years, under the David Elder Foundation, at the Royal Technical College, Glasgow. The guiding motive throughout each course of lectures was to familiarize the audience with the heavenly bodies, by knowing how to recognize the stars and constellations, and delighting in the wonderful discoveries associated with the name of each. In fact, the lecturer looked upon himself as a tourist-guide in a series of excursions over various parts of the heavens.

A careful selection from these lectures was published in Chambers’s Fournal ; and these, with some additions to the text, and illustrations, are now brought together. They do not aim at teaching the whole subject of astronomy, but rather at increasing the enjoyment and the wonder felt by everyone on a starry night, with all “the glory and the freshness of a dream” ; and they aim occasionally at putting things in a new setting which may be of interest to astronomers. While enjoying to the full the speculative hypotheses that are in vogue to-day, the author warns his readers against giving the same credence to such flights of the imagination as would be gratefully given to the contributions of those who have laid the solid foundations of Astronomy, the Queen of the Sciences.

The whole of this series of articles is interdependent, yet each one is self-contained. This arrangement necessarily involves some repetition, but only of matters so important in their application that the reader may be glad to have his attention directed to them more than once.

The last two chapters differ essentially from the first fifteen. They form a self-contained account of present-day speculation on the Origin of the Universe.

After this preface J must insert two wonderful ancient parallel poems, both of them expressing identically, and most beautifully, the emotions felt by most of us on a brilliant starry night. They were handed to me, as being interesting from their similarity, by the late Mr Humphry Ward, shortly before his death.

GEORGE ForBEs.

Tue SuHep, Pittocuris, July 1926.

THE WONDER AND THE GLORY OF THE STARS

When I consider the heavens, the work of thy fingers, the moon and the stars, which thou hast ordained ;

What is man, that thou art mindful of him? and the son of man, that thou visitest him?

Thou hast made him a little lower than the angels, and hast crowned him with glory and honour.

Thou madest him to have dominion over the works of thy hands; thou hast put all things under his feet. Psalm viii., The Psalmist

Claudius Ptolemeus the Astronomer, circa A.D. 180

Quoted in Mackail’s Anthology, iv. 32. Mackail’s translation is as follows :—

‘‘T know that I am mortal and ephemeral; but when I scan the multitudinous circling spirals of the stars, no longer do I touch earth with my feet, but sit with Zeus himself, and take my fill of the ambrosial food of gods.”’

Contents

CHAPTER

L II.

. How To KNOW THE PLANETS ; . rue PLranetr Mars , : j L

Chapter II I

In our latitudes the star-gazer’s year commences with the fall of the leaf, partly because in summer few hours remain after the long evenings of twilight when stars can be seen, and partly because after that time all of our favourite constellations begin to appear at eventide.

Some enthusiasts make a practice of beginning their astronomical year by staying out of doors from sunset to sunrise during the whole of one clear night, when there is no moonlight, in September. They can then witness the night’s procession of nearly all the stars, marching from left to right while they face the south. “Throughout this “‘ march past ” the stars retain their formations and relative positions, as if they were fixed to a vault of heaven which turns round an imaginary line drawn from the observer to the north star, Polaris.

During this night-watch nearly every star and constellation that ever shines in our sky is passed in review. Only those in that part of the heavens occupied by the sun, near Virgo, the Virgin, in September, are outshone by the sun at sunrise and sunset. So that on this ‘‘ New Year’s Eve’ of the star-lover nearly every old friend comes in turn to the saluting point and claims recognition.

Even those people who have not previously learned to call the stars by their names often find that this “all-night sitting” in September serves a purpose. It introduces them to that more intimate acquaintance with individual stars and constellations which gives always thereafter a new zest to their outlook on the heavens.

On a September evening the sight of Capella, at the head of the constellation Auriga, the Charioteer, over the north-eastern horizon, warns the old hand to look out, in the next few hours, for the rising in the east of Taurus, the Bull; Orion, the Hunter ; Gemini, the Twins, and all those brilliant stars which will, before the dawn, culminate in the most gorgeous star-picture that can ever be seen in the sky from any part of the earth’s surface.

Such a continuous study of the star-procession, from sunset to sunrise, at one or two dates in the year, helps to unite, into one whole, the various aspects of the sky as seen in the varying seasons and hours.

On any other night it is a good plan to spend a short time, always at the same hour, every clear evening, in the enjoyment of recognizing old friends among the stars and looking out for any new features. Besides the noting of the phases and place of the moon, this practice leads to watching the movements of planets among the stars. It may lead to the unexpected enjoyment of an exceptionally brilliant meteor-shower of superlative grandeur, as was my own good fortune in 1873, on the 23rd of November, when the lost comet of Biela reappeared as the finest meteor-shower I ever saw, always excepting the unique display of Leonids on the 13th November 1866.

The same habit may disclose to view on some night an unrecorded comet. But, best of all, the habit may lead anyone to the first discovery of a new star. “This luck must fall upon someone. In 1892 it was the luck of an Edinburgh man, Dr Anderson, who had the habit of interviewing the stars at 3 a.M. every night. And again, in 1902, in the same way, he was the first discoverer of a new star in Perseus, the brightest ever seen for about three hundred years. “These wonderful new stars are rare. “They rise to full brightness from invisibility in less than a day, and seldom remain visible to the naked eye for more than a month or two.

By choosing always the same hour for this interview with the stars, the order of procession from month to month, the same as from hour to hour, can be fixed in the mind. If a star-atlas (like Proctor’s pocket one) and a flashlight be always used, anyone will be able, in a year or two, to name every star that he can see, some three or four thousand in all. “The beginner may also procure a planisphere for a few shillings, to show on a circular card what constellations can be seen at any hour in any month. Later he will be able to do this in his head.

II

Suppose, then, that on a moonless September night, say between 7 and 8 p.M., one begins an all-night study of the brighter stars in a the south that follow each other from left to right throughout the dark hours. Which are the brightest stars to be seen at that hour ? There are three, in different parts of the sky, that will catch the eye as being quite the most resplendent—one in the west, one overhead, and one to the east of north.

Nearly overhead is Vega, or Alpha of the Lyre constellation, shining with a soft steel-blue colour. “Then in the west, above the still sunset-flushed part of the horizon, Arcturus flashes in a solitary grandeur with an orange tint. Lastly, a little east of true north, just as high above the horizon as Arcturus was seen in the west, the brilliant Capella shines yellow. Capella is at the head of a C-shaped string of stars, not all risen yet, forming the constellation Auriga, the Charioteer.

Besides these three first-magnitude stars, Vega, Arcturus, and Capella, there are many others to claim special attention at this hour, 8 p.m. in September. Half-way down from Vega to the southern horizon the bright Altair is recognized by his having two less bright companions, all in one straight line pointing up to Vega. Altair is the brightest star in the constellation Aquila, the Eagle.

Looking up again at Vega, the five brightest stars in its neighbourhood take the form of a long Roman cross, and make up the constellation Cygnus, the Swan. If the night be really clear, the Milky Way in this region will be seen to be divided into two luminous branches that meet at the Swan constellation.

Altair in the Eagle being now half-way from the Zenith to the south horizon, a glance to the left of it reveals a great square with four bright stars at the four corners. This constellation is the great square of Pegasus, and its two upright sides point to the Pole-star.

_ From the top left-hand corner of this very conspicuous square a string of three bright stars run to the left, being part of the constellation Andromeda (Fig. 3).

If the observer now examines the northern sky, other groups of stars, or constellations, are noted. At this hour, 8 p.m. in September, the seven stars known in this country as the Plough are very low down a little west of the north, It is part of the constellation Ursa Major, the Great Bear. It is a guide to other stars, Four of the seven stars form the ploughshare. ‘The other three are the curved shaft of the plough or the tail of the bear.

It is a useful hint for beginners to remember that the natural advance of the plough, towards Capella, shows the direction in which all the stars are rotating round the Pole-star (see Fig. 2).

The two end stars of the ploughshare are called the pointers, because they point to the Pole-star, fairly high up in the north. A line from the middle of the plough through this Pole-star leads to the constellation Cassiopeia, or Cassiopeia’s Chair. At this hour it a Fersei

6b Ferse/

Pegasus a ¢

Fic, 3.—The Square of Pegasus, Andromeda, and a Persei. B Persei is Algol, the wonderful variable Star, Due south at midnight in September is right above Capella, already identified. ‘The five stars of this constellation, if joined by imaginary lines, would form a W written in the sky, so Cassiopeia cannot be mistaken.

Return now to the Great Bear. If you carry the eye along the curve of its tail, and beyond, it comes to Arcturus, already noted as setting in the west. This is a useful way for identifying Arcturus at any time. “The same curved line carried on an equal distance beyond Arcturus would lead to Spica, the brightest star in Virgo, the Virgin. At this hour, however, Spica is below the horizon. In fact, during September, the sun is close to Spica, and prevents it from being seen (Fig. 4).

When to the glory of the few stars that have now been named 1s added the general impression of the less conspicuous ones, we have before us now, at 8 p.m. in September, a truly wonderful panorama.

THE GLORY OF SEPTEMBER STARS o hey

But it is as nothing when compared with the glory that is about to arise out of the eastern horizon in the next few hours, heralded by Capella and the C-shaped Auriga.

‘The same panorama which we see at 8 p.m. in September, with the same stars in the same positions as now over the landscape, will be seen one month later and two hours earlier, or two months

FMA |

& POH Fag s x * ‘ * Ursa Major i 2% x Corona

x Arcturus Spica |

Fic. 4.—The curve of the Bear’s Tail if prolonged passes through Arcturus and Spica. Due south at midnight in April later and four hours earlier—that is to say, at 6 p.m. in October, or at 4. P.M. in November.

So also exactly the same panorama would have been seen, in the same positions as now over the landscape, one month earlier and two hours later, or two months earlier and four hours later—that is to say, at 10 P.M. in August, or at midnight in July. It is always a change of two hours for each month.

Il

Having now surveyed the constellations at 8 p.M., we note that a great change occurs in the next four hours. By 10 p.m. in September Arcturus has set in the west, and Vega has climbed down from her

28 THE WONDER & THE GLORY Of THE Sine great altitude. But it is to Capella, the third of our brightest stars, and to her neighbours now risen or about to rise above the horizon, that the gaze of any watcher must be directed from now onwards (Fig. 5).

At 10 p.m. Capella is twice as high above the horizon. And now she shows herself as the queen of a string of five stars, shaped like a

VEEN andl 8 ZR TEL Fic.*5.—Capella in Auriga, rising in the N.E, on a September evening, heralding the greatest glory among the Stars capital C, which at this hour lies nearly on its back. All these five stars belong to the constellation Auriga, the Charioteer, except the bottom one, which happens to belong to the neighbouring constellation, Taurus, the Bull, now coming into view as the herald of the more splendid Orion. The king of the constellation Taurus is a ruddy star, just risen, and its name is Aldebaran. It is of the first magnitude. Above Capella, at this auspicious hour, is the W-shaped Cassiopeia.

After another two hours—that is to say, by midnight in September—the grandest constellation of all, Orion, the Hunter, is coming into view below Aldebaran. At this hour Orion has not yet assumed an upright position as the bold hunter, but is fixed in an inclined position, leaning to our left.

Hour after hour the star-gazer will watch the gradual marching of Orion to the right, and his gradual assumption of a more and more upright position owing to his turning with all the constellations round the Pole-star high up in the north, behind us.

In September the watch on Orion will have to be prolonged to sunrise before this splendid group of stars reaches an erect attitude

Fic, 6.—The Lion, whose head resembles a reaper’s sickle. Due south at midnight in February in the south. By that time Capella has reached a position overhead, far above the head of Orion.

During these early morning hours of the September night a succession of superb stars have risen in the east and mounted higher. First come Castor and Pollux, the golden pair of Twins ; then Procyon, followed by Sirius, the Dog-star, the greatest star of all. Half-an-hour later, at 3 a.m. in September, Leo, the Lion, rises in the east. It is unmistakable, because a line drawn through six prominent stars in Leo takes the form of a reaper’s sickle, with the very bright star Regulus at the end of the handle (Fig. 6).

And finally, towards the hour of sunrise in September, Orion stands erect. “Iwo bright stars mark his shoulders ; two more his legs. ‘Three little stars indicate the head. But the three stars, ina line nearly horizontal, that mark his belt, with others suggesting a sword hanging therefrom, is the feature that identifies him best. The more so because these three stars point down to the left towards the superb Sirius, and upwards on the right towards the ruddy Aldebaran.

Sirlus and Aldebaran are the feet of an arch of magnificent stars that frame the picture of Orion. This jewelled arch includes Sirius,

% Castor aK Pollux & Capella

Aldebaran a

Hue pi Pleiades picture of Stars in any part of the heavens, Orion in centre surrounded by Sirius, Procyon, Pollux and Castor, Capella, Aldebaran, with Hyades and Pleiades to the right; as at 9 p.m. in March.

Procyon, Castor, Pollux and Aldebaran, some of the most beautiful of all stars (Fig. 7).

This picture is even more impressive, from the symmetry of the attendant arched frame of stars, three or four hours after Orion was in the south, say at 9 p.m. in March.

The splendour of the six stars is overwhelming, and no star in the heavens can rival Sirius, a star upon whose magnificence every human eye must be riveted in silent admiration. Yet, however much the jewelled frame may enhance the picture of Orion, it is the seven principal stars of that constellation itself with their immediate attendants, due south of us, that fascinate the beholder ee ee ee at midnight of Christmas time, towards sunrise in September, or soon after sunset in March. ‘This wonderful spectacle, with the encircling frame of such giants as Aldebaran, Capella, Castor, Pollux, Procyon and Sirius, creates a picture so complete, so exquisite, that no single one among them, not even Sirius, can for the moment claim more honour than as being a unit in this most superb illumination, a prospect which has drawn forth the admiration of all nations for a hundred generations, nay, for as long as men have been upon our planet.

IV

And now the ten-hour watch in September is over. We have noted the key-stars and constellations from Arcturus which set soon after the sun, followed by the Cross of Cygnus at the fork of the Milky Way, and Vega. Then came Altair of the Eagle, and the great Square of Pegasus with Andromeda. The stars which rose during the period of our watch began with Capella’s constellation Auriga, the Charioteer. It was followed by Aldebaran of the Bull, and later by Orion, and the twins Castor and Pollux, by Procyon and Sirius, and finally by Leo, the Lion. ‘Thereafter, Virgo, the Virgin, was due to rise, but, that region being now occupied by the sun, sunrise closed the diorama near the bright star Spica of the Virgin, and we have been able to pass in review nearly all stars from Virgo to Virgo.

Armed with an Easy Guide to the Constellations, a star-atlas or a planisphere, and a flashlight, this ten-hour tour of the heavens may be undertaken without further guidance. The same accessories, if used for half-an-hour at a fixed time on every clear night, will give a steadily increasing pleasure to anyone who wants to know the names of the stars and the order of their succession in the nightly review.

Having thus acquired a bowing acquaintance with the monarchs _ of the firmament, many a watcher will seek a more intimate friendship. Old-fashioned geography, dealing with the towns of the world, was content to indicate their position. “The new geography expects its students to know about the manufactures and commerce of each town, its architecture, museums, art collections, and so

32 THE WONDER ‘S& THE GLORY OF THE Dia ke forth. So it is with astronomy. In old days people were content to know the position of each star. Now we want to know in which direction it is moving, and what it is made of. Whether it is constant in brightness, or variable, and whether it is single or attracted by a companion, revolving in a definite orbit. Is it associated with other stars of any well-determined stream ? What affinities does it . possess in common with any other groups of stars, If our coloursense be good, we notice that Vega is bluish, the Orion stars greenish, Capella yellow, Arcturus orange, Betelgeuse and Antares of the Scorpion red. In the new astronomy we want to classify all - ~ the stars in this way, and to know the meaning of these tints of colour.

It is evident that anyone who has learnt the names and places of the principal stars is sure to go on and learn what has already been done by astronomers to know the character of each star, like Vega for instance. Why does Betelgeuse, at Orion’s right shoulder, differ in colour from Rigel and the other stars in Orion ? Are Castor and Pollux really so twin-like as they seem ? Or, in what points do they differ? Is there any kind of physical connection between the individual stars that seem to be associated in one constellation, like the seven big stars of the Plough? Which stars are nearest to us, and which of the bright ones are most distant ?

‘The answers to many of these questions, so far as they are known, are often hidden away in the pericdical literature of astronomy. Occasionally a historian of our science, Miss Agnes Clerke, for example, has delighted us with a summary, or connected story, of these discoveries. But it is soon out of date, and the earnest student has the great happiness of being himself the discoverer of all these discoveries, in the periodical astronomical literature available in some library.

Either in that way, or else by the help of a friend who has made himself acquainted with recent astronomical observations and discoveries, the star-gazer can realize a new form of enjoyment by a more personal contact with the different stars.

The present writer, immediately on recognizing any particular star, has his memory alive with most delightful ideas that are associated with the star. “This outlook is probably shared by all astronomers, each one furnished with his own series of associations, and it is part of the great uplifting emotion that is always to them the accompaniment of a clear, starry night.

V

To explain what is meant, let us take any simple case—some bright star. Let us praise, for example, the glory of Arcturus, because after this month of September it will have ceased to shine upon us, being then approached too closely by the sun.

It so happens that I never see Arcturus without recalling the fact that this was one of the first three stars whose places were found by Halley, two centuries ago, to be sensibly changed since the time when they were recorded by the ancient Greeks, or even since [’ycho Brahe.

Halley, one of our great Astronomers Royal, found that, since the days of Hipparchus, Arcturus has moved among the other stars through a distance actually amounting to two and a half times the apparent diameter of the moon.

And since, more recently, the distance of this star from us has been measured, we now know that this means that the motion of Arcturus, at right angles to our line of sight, is at the prodigious rate of two hundred and eighty-eight miles every second, and that it is now eighteen million million miles away from the position in which it was marked by Hipparchus.

‘The thoughts then wander to the proper-motions of other stars, to the ingenious device now being used by Eddington and by the Astronomer Royal, at Cambridge and Greenwich observatories, for superposing star-negatives photographed at two dates twenty or thirty years apart. In this way even minute motions of the stars are being detected and measured. ‘Then the thoughts about Arcturus carry us in admiration to the great American catalogue of the proper motions of twelve thousand stars. And we then recall how Eddington, by the use of this catalogue, was able to confirm Kapteyn’s marvellous discovery of systematic motions among the stars.

Twenty years ago Kapteyn, of Holland, made a most surprising discovery—that most of the stars belong to one or other of two great star-streams that are travelling in opposite directions.

c

There are many other smaller swarms of stars, each swarm having its own velocity and its own direction of motion. But Kapteyn’s two opposing star-streams are the greatest wonder of all.

So much for the glory of Arcturus and proper-motions. A similar kind of association of ideas is aroused by the glory of Vega, Capella, Sirius, the Great Bear, or the Pleiades. Each has a totally different story to tell, always full of interest.

So it may well happen that many a beginner who spends a whole September night with the stars goes on to recognize individual peculiarities. “Chen, passing from guide-books and atlases, he may himself become an explorer among the orbs of heaven with the help of a telescope. Once started in this way, there are few who would not seek, by books and companionship, to become real students of the most sublime of all the sciences. Some of these enthusiasts, if perseverance upheld them, might add to the discoverles which rejoice the hearts of all real astronomers.

So the all-night sitting in September has led us on to great thoughts about the heavenly hosts. It has also exposed to us, hour by hour, the changing aspects of the night sky that we shall behold in the evenings from month to month during the winter.

oo >|

GEAR TERATTT

I

Everyone who has seen ‘Turner’s picture of the Dogana, Venice, or even the fine engraving of it, must have felt that it owes not a little of its charm to the bright evening star shining in the glow of sunset. Many an artist besides “Turner has known how to catch, on astill evening, the soft beauty of Venus beneath the thin crescent of the young moon, as a part of his sunset-picture, say, of the warships in Portsmouth harbour. Or, at that hour, he has been able to add something to the pink antiglow of sunset in the east, by choosing an evening when ‘Jupiter and the full moon are reflecting their beams on the harbour’s ripples.

Jupiter, Venus and the other planets (that is, wanderers) differ from the rest of the stars in two respects. “They are not fixed, but move about from one constellation of stars to another. And again, each of them varies in brightness from month to month, and it is only now and then that any one of them actually compels our attention, unless we are very careful watchers of the stars.

It may surprise some of the less careful watchers to know that there are only five of these planets ever visible to the naked eye. All of them are occasionally very bright. “They are Mercury, Venus, Mars, Jupiter and Saturn. And for practical purposes Mercury may be left out of account, because he is small and, being never more than twenty-three degrees away from the sun, he is seldom seen in our climate.

The four principal planets, brilliant lamps of the sky, are admired by all, and often we hear the query : “ What is that lovely star we see every evening now in the west?” ‘I’he answer Is very sure to be : ‘‘ The planet Venus”’—a round planet that shows in a telescope all the phases of the moon, but in a year and a half instead of one month.

Sometimes the query may take this form: “ Before going to bed, lately, we have been noticing a wonderful great star in the south. What star is it?”’ “The answer will be: “‘It must be a planet—either Mars, Jupiter or Saturn.” An astronomer might, of course, know which of them is in that direction at that time. But a moment’s inspection would suffice to make this known to anyone who cares enough about the stars to notice things for himself.

It is certainly a pleasure to know some of the fixed stars by name ; but they are always in the same place among the others, and of the same brightness, except in hazy weather. It is a much greater pleasure to find a planet in its wanderings, and to be able to welcome Mars or Jupiter by name after many months of absence.

Everybody knows about the solar system—that you can make a rough representation of it on a flat plane table by putting a ball in the middle of the table for the sun, and drawing circles on the table for the orbits of the planets. “These would be represented by little balls moving on the circles all in one direction (anti-clockwise, if we suppose ourselves to be looking at the table from the northern hemisphere). And the planets in the smaller circles move quicker than those in the larger circles. Of course it is also well known that the orbits of different planets are not exactly circles, but ovals, and they are very slightly tilted to the table, on whose surface our earth is supposed to move. But the tilt is found to be very small, and need not be considered at first (Figs. 8 and 9).

Now it is all very well to say that everybody knows this because he has read it in a book, but it is far better if we can find it out for ourselves. “Then we shall be able to distinguish the planets from other stars and from each other, and this is what the books do not generally tell us.

rt

There are three ways of knowing a planet as such when we see it. ‘The first two are very quick and easy to apply, but not so certain as the third. The first clue is this : Whenever you see an unusually bright star, unless it be Sirius, it is probably a planet, in that part of its orbit where it becomes brightest to the inhabitants of our planet the Earth. Take Venus, for instance, ona circle that is always inside the earth’s orbit. She does not shine by her own light. The half of her next the sun is lighted by the sun ; the rest of her is dark to us. So, when Venus is nearest to us, we are looking at her dark side, which is invisible. When she moves a little away from there we