[15] Already in the ancient book of Job, whose hero has quite the characteristics of a Nomadic Emir, we find some astronomical terms whose analogy with the true Arabic star-names is unmistakable. See Job, ix. 9; xxxviii. 31, 32.
ASTRONOMY WITHOUT A TELESCOPE.—J. E. Gore
It must be remembered that astronomy was studied ages before the invention of the telescope, and that the ancient astronomers gained, without any optical assistance, a considerable amount of knowledge respecting the heavenly bodies.
Let us first consider the stars visible to the naked eye. The number of these down to the sixth magnitude—about the faintest that average eyesight can see—is, for both hemispheres, about 6,000. The number, therefore, visible at one time from any given place is about 3,000. Possibly double this number might be seen by those gifted with exceptionally keen eyesight; but even this is a comparatively small number, scattered as it is over so large an area. Those who do not possess the power of effective enumeration estimate the number visible to the naked eye as considerably greater than is really the case. This is partly due to the irregular distribution of the lucid stars over the celestial vault, and partly to the effect which the aspect of the starry sky produces on the imagination; the fact of the stars increasing in number as they diminish in brightness inducing us to suspect the presence of points of light which we do not actually see. An attempt to count those visible with certainty in any selected portion of the sky will, however, convince any intelligent person that the number, far from being large, is really very small, and that the idea, which some entertain, of a countless multitude is merely an optical illusion, and a popular fallacy which has no foundation in fact. Of course, the number visible in telescopes is very considerable. Perhaps with the largest telescopes 100,000,000 could be seen; but even this large number is very far from being “countless.” The present population of the earth is about 1,400,000,000, or about fourteen times the number of the visible stars!
The first thing to be done in studying the heavens with the naked eye is to learn the positions and names of the brighter stars; and from these the fainter ones may easily be identified by means of a star atlas. Those who study the stars in this way have probably a more intimate knowledge of the starry heavens than professional astronomers, who generally find the stars—at least the fainter ones—by referring to a catalogue of stars, and then setting their telescope to the place indicated by the figures given in the catalogue. Although the famous astronomer Sir William Herschel possessed several large telescopes, he also studied the stars with the naked eye, and it is related of this great observer that he could without hesitation identify any star he could see in this way by its name, letter, or number! Such an exhaustive knowledge of the heavens is, of course, very rare; but an acquaintance with all the brighter stars can easily be acquired by any person of ordinary intelligence.
The “Plow,” or Great Bear,[16] is familiar to most people. This remarkable group of seven stars will be found very useful in identifying some of the brighter stars. The two stars furthest from the “tail” are called “pointers,” as they point nearly to the Pole Star, or star to which the axis of the earth nearly points. I say “nearly,” for the Pole Star is not exactly at the pole, but distant from it about three diameters of the moon. The northern of these stars is known to astronomers by the Greek letter Alpha and the southern as Beta. The others, following the order of the figure, are known by the letters Gamma, Delta (the faintest of the seven), Epsilon, Zeta, and Eta.[17] Now, if the curve formed by the three stars in the tail, Epsilon, Zeta, and Eta, is continued on, it will pass near a very bright star. This is Arcturus (Alpha of the constellation Boötes), one of the brightest stars visible. Again, if we draw an imaginary line from Gamma to Beta, and produce it, it will pass near another bright star. This is Capella (Alpha of Auriga, “the Charioteer” referred to by Tennyson).
Again, if we draw a line from Delta to Beta, and produce it, it will pass near the tolerably bright stars, Castor and Pollux (Alpha and Beta of the constellation Gemini, or the Twins), the northern of the two being Castor. Another line from Delta to Gamma produced will pass near a bright star called Regulus (Alpha of Leo, the Lion). Another line from Beta to Eta will pass near a group called Corona Borealis, or the Northern Crown.
Constellation of Orion, showing the Belt and Sword
On the opposite side of the Pole Star from the Plow, a group of five conspicuous stars will be found, forming a figure shaped somewhat like a W. This is Cassiopeia’s Chair. Commencing with the most westerly of the five, these stars are known as Beta, Alpha, Gamma, Delta, and Eta. Like the stars of the Plow, those of Cassiopeia’s Chair may be used to find other stars. For instance, a line drawn from Beta to Alpha passes close to a star known as Gamma in Andromeda; and the same line produced in the opposite direction will pass a little north of the bright star Vega (Alpha Lyræ), one of the brightest stars in the northern heavens. A line from Gamma to Alpha produced will pass through the well-known “Square of Pegasus.”