CONCLUDING CHAPTER.
HOW TO NAME THE STARS.
Every one who wishes to learn something about astronomy should make a determined effort to become acquainted with the principal constellations, and to find out the names of the brighter and more interesting stars. I have therefore added to Star-land this little chapter, in which I have tried to make the study of the stars so simple that, by taking advantage of a few clear nights, there ought to be no difficulty in obtaining a knowledge of a few constellations.
The first step is to become familiar with the Great Bear, or Ursa Major, as astronomers more generally call the group. We begin with this, because after it has been once recognized, then you will find it quite easy to make out the other constellations and stars. It may save you some trouble if you can get some one to point out to you the Great Bear; but even without such aid, I think you will be able to make out the seven bright stars which form this remarkable group, from the figure here given ([Fig. 92]). Of course, the position of this constellation, as of every other in the heavens, changes with the hour of the night, and changes with the seasons of the year. About April the constellation at 11 o’clock at night is high over your head. In September at the same hour, the Great Bear is low down in the north. It is to be seen in the west in July, and at Christmas it lies in the east at convenient hours in the evening for observation. One of the advantages of using the Great Bear as the foundation of our study of the stars arises from the fact that to an observer in the British Islands or in similar latitudes this group never sets. Whenever the sky is clear after nightfall, the Great Bear is to be seen somewhere, while the brightness of its component stars makes it a conspicuous object. Indeed, there is only one constellation in the sky, namely, that of Orion, which is a more brilliant group than the Great Bear. We shall tell you about Orion presently, but it does not suit to begin with, because it can only be seen in winter, and is then placed very low down in the heavens.
Fig. 92.—The Great Bear and the Pole Star.
Your next lesson will be to utilize the Great Bear for the purpose of pointing out the Pole Star. Look at the two stars marked α and β. They are called the “Pointers,” because if you follow the direction they indicate along the dotted line in the figure, they will conduct your glance to the Pole. This is the most important star in the heavens to astronomers, because it happens to mark very nearly the position of the Pole on the sky. You will easily note the peculiarity of the Pole Star if you will look at it two or three times in the course of the night. It will appear to remain in the same place in the sky, while the other stars change their places from hour to hour. It is very fortunate that we have a star like this in the northern heavens; the astronomers in Australia or New Zealand can see no bright star lying near the Southern Pole which will answer the purposes that the Pole Star does so conveniently for us in the north.
The Pole Star belongs to a constellation which we call the Little Bear; two other conspicuous members of this group are the two “Guards”; you will see how they are situated from [Fig. 82], [p. 322]. They lie nearly midway between the Pole Star and the last of the three stars which form the Great Bear’s Tail. The same figure will also introduce us to another beautiful constellation, namely, Cassiopeia. You will never find any difficulty in identifying the figure that marks this group if you will notice that the Pole lies midway between it and the Great Bear.
Fig. 93.—The Great Square of Pegasus.
Cassiopeia is also one of the constellations that never set to British observers; but now we have to speak of groups which do set, and which, therefore, can only be observed when the proper season comes round. The first of these is “the Great Square of Pegasus”; you cannot see this group conveniently in the spring or summer, but during the autumn and winter it is well placed after nightfall. There are four conspicuous stars forming the corners of the square, and then three others marked α, γ, and β ([Fig. 93]), which form a sort of handle to the square. In fact, if you once recognize this group, you will perhaps see in it a resemblance to a great saucepan with a somewhat bent handle, and then you will be acquainted with a large tract of Star-land near the Square of Pegasus. From the figure you will see that a line imagined to be drawn from the Pole Star over the end of Cassiopeia, and then produced as far again, will just lead to the Great Square. I have also marked on this figure two objects that are of great telescopic interest; one of them is the Nebula in Andromeda, of which we had an account in the last lecture. You see it lies halfway between the corner α of the square and the group of Cassiopeia. Another interesting object is the star marked γ Andromedæ. The telescope shows it to consist of a pair of stars, the colors of which are beautifully contrasted.