The Story of the Heavens

The Constellations—The Great Bear and the Pointers—The Pole Star—Cassiopeia—Andromeda, Pegasus, and Perseus—The Pleiades: Auriga, Capella, Aldebaran—Taurus, Orion, Sirius; Castor and Pollux—The Lion—Boötes, Corona, and Hercules—Virgo and Spica—Vega and Lyra—The Swan. The student of astronomy should make himself acquainted with the principal constellations in the heavens. This is a pleasing acquirement, and might well form a part of the education of every child in the kingdom. We shall commence our discussion of the sidereal system with a brief account of the principal constellations visible in the northern hemisphere, and we accompany our description with such outline maps of the stars as will enable the beginner to identify the chief features of the starry heavens. In an earlier chapter we directed the attention of the student to the remarkable constellation of stars which is known to astronomers as Ursa Major, or the Great Bear. It forms the most conspicuous group in the northern skies, and in northern latitudes it never sets. At eleven p.m. in the month of April the Great Bear is directly overhead (for an observer in the United Kingdom); at the same hour in September it is low down in the north; at the same hour July it is in the west; by Christmas it is at the east. From the remotest antiquity this group of stars has attracted attention. The stars in the Great Bear were comprised in a great catalogue of stars, made two thousand years ago, which has been handed down to us. From the positions of the stars given in this catalogue it is possible to reconstruct the Great Bear as it appeared in those early days. This has been done,[Pg 410] and it appears that the seven principal stars have not changed in this lapse of time to any large extent, so that the configuration of the Great Bear remains practically the same now as it was then. The beginner must first obtain an acquaintance with this group of seven stars, and then his further progress in this branch of astronomy will be greatly facilitated. The Great Bear is, indeed, a splendid constellation, and its only rival is to be found in Orion, which contains more brilliant stars, though it does not occupy so large a region in the heavens. Fig. 80.—The Great Bear and Pole Star. [Pg 411] Fig. 81.—The Great Bear and Cassiopeia. In the first place, we observe how the Great Bear enables the Pole Star, which is the most important object in the northern heavens, to be readily found. The Pole Star is very conveniently indicated by the direction of the two stars, β and α, of the Great Bear, which are, accordingly, generally known as the "pointers." This use of the Great Bear is shown on the diagram in Fig. 80, in which the line β α, produced onwards and slightly curved, will conduct to the Pole Star. There is no likelihood of making any mistake in this star, as it is the only bright one in the neighbourhood. Once it has been seen it will be readily identified on future occasions, and the observer will not fail to notice how constant is the position which it preserves in the heavens. The other stars either rise or set, or, like the Great Bear, they dip down low in the north without actually setting, but the Pole Star exhibits no considerable changes. In summer or winter, by night or by day, the Pole Star is ever found in the same place—at least, so far as ordinary observation is concerned. No doubt, when we use the accurate instruments of the observatory the notion of the fixity of the Pole Star[Pg 412] is abandoned; we then see that it has a slow motion, and that it describes a small circle every twenty-four hours around the true pole of the heavens, which is not coincident with the Pole Star, though closely adjacent thereto. The distance is at present a little more than a degree, and it is gradually lessening, until, in the year A.D. 2095, the distance will be under half a degree. The Pole Star itself belongs to another inconsiderable group of stars known as the Little Bear. The two principal members of this group, next in brightness to the Pole Star, are sometimes called the "Guards." The Great Bear and the Little Bear, with the Pole Star, form a group in the northern sky not paralleled by any similarly situated constellation in the southern heavens. At the South Pole there is no conspicuous star to indicate its position approximately—a circumstance disadvantageous to astronomers and navigators in the southern hemisphere. It will now be easy to add a third constellation to the two already acquired. On the opposite side of the Pole Star to the Great Bear, and at about the same distance, lies a very pleasing group of five bright stars, forming a W. These are the more conspicuous members of the constellation Cassiopeia, which contains altogether about sixty stars visible to the naked eye. When the Great Bear is low down in the north, then Cassiopeia is high overhead. When the Great Bear is high overhead, then Cassiopeia is to be looked for low down in the north. The configuration of the leading stars is so striking that once the eye has recognised them future identification will be very easy—the more so when it is borne in mind that the Pole Star lies midway between Cassiopeia and the Great Bear (Fig. 81). These important constellations will serve as guides to the rest. We shall accordingly show how the learner may distinguish the various other groups visible from the British Islands or similar northern latitudes. The next constellation to be recognised is the imposing group which contains the Great Square of Pegasus. This is not, like Ursa Major, or like Cassiopeia, said to be "circumpolar."[Pg 413] The Great Square of Pegasus sets and rises daily. It cannot be seen conveniently during the spring and the summer, but in autumn and in winter the four stars which mark the corners of the square can be easily recognised. There are certain small stars within the region so limited; perhaps about thirty can be counted by an unaided eye of ordinary power in these latitudes. In the south of Europe, with its pure and bright skies, the number of visible stars appears to be greatly increased. An acute observer at Athens has counted 102 in the same region. Fig. 82.—The Great Square of Pegasus. The Great Square of Pegasus can be reached by a line from the Pole Star over the end of Cassiopeia. If it be produced about as far again it will conduct the eye to the centre of the Great Square of Pegasus (Fig. 82). The line through β and α in Pegasus continued 45° to the south points out the important star Fomalhaut in the mouth of the Southern Fish. To the right of this line, nearly half-way down, is the rather vague constellation of Aquarius, where a small equilateral triangle with a star in the centre may be noticed. The square of Pegasus is not a felicitous illustration of[Pg 414] the way in which the boundaries of the constellations should be defined. There can be no more naturally associated group than the four stars of this square, and they ought surely to be included in the same constellation. Three of the stars—marked α, β, γ—do belong to Pegasus; but that at the fourth corner—also marked α—is placed in a different figure, known as Andromeda, whereof it is, indeed, the brightest member. The remaining bright stars of Andromeda are marked β and γ, and they are readily identified by producing one side of the Square of Pegasus in a curved direction. We have thus a remarkable array of seven stars, which it is both easy to identify and easy to remember, notwithstanding that they are contributed to by three different constellations. They are respectively α, β, and γ of Pegasus; α, β, and γ of Andromeda; and α of Perseus. The three form a sort of handle, as it were, extending from one side of the square, and are a group both striking in appearance, and useful in the further identification of celestial objects. β Andromedæ, with two smaller stars, form the girdle of the unfortunate heroine. α Persei lies between two other stars (γ and δ) of the same constellation. If we draw a curve through these three and prolong it in a bold sweep, we are conducted to one of the gems of the northern heavens—the beautiful star Capella, in Auriga (Fig. 83). Close to Capella are three small stars forming an isosceles triangle—these are the Hœdi or Kids. Capella and Vega are, with the exception of Arcturus, the two most brilliant stars in the northern heavens; and though Vega is probably the more lustrous of the two, yet the opposite opinion has been entertained. Different eyes will frequently form various estimates of the relative brilliancy of stars which approach each other in brightness. The difficulty of making a satisfactory comparison between Vega and Capella is greatly increased by the wide distance in the heavens at which they are separated, as well as by a slight difference in colour, for Vega is distinctly whiter than Capella. This contrast between the colour of stars is often a source of uncertainty in the attempt to compare[Pg 415] their relative brilliancy; so that when actual measurements have to be effected by instrumental means, it is necessary to compare the two stars alternately with some object of intermediate hue. Fig. 83.—Perseus and its Neighbouring Stars. On the opposite side of the pole to Capella, but not quite so far away, will be found four small stars in a quadrilateral. They form the head of the Dragon, the rest of whose form coils right round the pole. If we continue the curve formed by the three stars γ, α, and δ in Perseus, and if we bend round this curve gracefully into one of an opposite flexion, in the manner shown in Fig. 83, we are first conducted to two other principal stars in Perseus, marked ε and ζ. The region of Perseus is one of the richest in the heavens. We have here a most splendid portion of[Pg 416] the Milky Way, and the field of the telescope is crowded with stars beyond number. Even a small telescope or an opera-glass directed to this teeming constellation cannot fail to delight the observer, and convey to him a profound impression of the extent of the sidereal heavens. We shall give in a subsequent paragraph a brief enumeration of some of the remarkable telescopic objects in Perseus. Pursuing in the same figure the line ε and ζ, we are conducted to the remarkable little group known as the Pleiades. Fig. 84.—The Pleiades. The Pleiades form a group so universally known and so easily identified that it hardly seems necessary to give any further specific instructions for their discovery. It may, however, be observed that in these latitudes they cannot be seen before midnight during the summer. Let us suppose that the search is made at about 11 p.m. at night: on the 1st of January the Pleiades will be found high up in the sky in the south-west; on the 1st of March, at the same hour, they will be seen to be setting in the west. On the 1st of May they are not visible; on the 1st of July they are not visible; on the 1st of September they will be seen low down in the east. On the 1st of November they will be high in the heavens in the south-east. On the ensuing 1st of January the Pleiades will be in the same position as they were on the same date in the previous year, and so on from year to year. It need, perhaps, hardly be explained here that these changes are not