Astronomy for Amateurs

which we shall return in the next chapter, i.e., the telescope resolves it into two marvelous suns, one of which is topaz-yellow, and the other emerald-green. Three stars, indeed, are visible with more powerful instruments. Fig. 7.—Perseus, the Pleiades, Capella. Above β and near a small star, is visible a faint, whitish, luminous trail: this is the oblong nebula of Andromeda, the first mentioned in the history of astronomy, and one of the most beautiful in the Heavens, perceptible to the unaided eye on very clear nights. The stars α, β and γ of Perseus form a concave bow which will serve in a new orientation. If it is prolonged in the direction of δ, we find a very brilliant star of the first magnitude. This is Capella, the Goat, in the constellation of the Charioteer (Fig. 7). If coming back to δ in Perseus, a line is drawn[Pg 39] toward the South, we reach the Pleiades, a gorgeous cluster of stars, scintillating like the finest dust of diamonds, on the shoulder of the Bull, to which we shall come shortly, in studying the Constellations of the Zodiac. Not far off is a very curious star, β of Perseus, or Algol, which forms a little triangle with two others smaller than itself. This star is peculiar in that, instead of shining with a fixed light, it varies in intensity, and is sometimes pale, sometimes brilliant. It belongs to the category of variable stars which we shall study later on. All the observations made on it for more than two hundred years go to prove that a dark star revolves round this sun, almost in the plane of our line of sight, producing as it passes in front of it a partial eclipse that reduces it from the second to the fourth magnitude, every other two days, twenty hours, and forty-nine minutes. And now, let us return to the Great Bear, which aided us so beneficently to start for these distant shores, and whence we shall set out afresh in search of other constellations. If we produce the curved line of the tail, or handle, we encounter a magnificent golden-yellow star, a splendid sun of dazzling brilliancy: let us make our bow to Arcturus, α of the Herdsman, which is at the extremity[Pg 40] of this pentagonal constellation. The principal stars of this asterism are of the third magnitude, with the exception of α, which is of the first. Alongside of the Herdsman is a circle consisting of five stars of the third and fourth magnitude, save the third, α, or the Pearl, which is of the second magnitude. This is the Corona Borealis. It is very easily recognized (Fig. 8). Fig. 8.—To find Arcturus, the Herdsman, and the Northern Crown. A line drawn from the Pole-Star to Arcturus forms the base of an equilateral triangle, the apex of which, situated opposite the Great Bear, is occupied by Vega, or α of the Lyre, a splendid diamond of ideal purity scintillating through the ether. This magnificent star, of first magnitude, is, with Arcturus, the most luminous in our Heavens. It burns with a white light, in the proximity of the Milky Way, not far from a constellation that is very easily recognized by the arrangement of its principal stars in the form of a cross. It is named Cygnus, the Bird, or the Swan (Fig. 9), and is[Pg 41] easy to find by the Square of Pegasus, and the Milky Way. This figure, the brilliancy of whose constituents (of the third and fourth magnitudes) contrasts strongly with the pallor of the Milky Way, includes at its extremity at the foot of the Cross, a superb double star, β or Albirio: α of Cygnus is also called Deneb. The first star of which the distance was calculated is in this constellation. This little orb of fifth magnitude, which hangs 69,000,000,000,000 kilometers (42,000,000,000,000 miles) above our Earth, is the nearest of all the stars to the skies of Europe. Fig. 9.—The Swan, Vega, the Eagle. Not far off is the fine Eagle, which spreads its wings in the Milky Way, and in which the star Altaïr, α, of first magnitude, is situated between its two satellites, β and γ. The Constellation of Hercules, toward which the[Pg 42] motions of the Sun are impelling us, with all the planets of its system, is near the Lyre. Its principal stars can be recognized inside the triangle formed by the Pole-Star, Arcturus, and Vega. All the Constellations described above belong to the Northern Hemisphere. Those nearest the pole are called circumpolar. They revolve round the pole in twenty-four hours. Having now learned the Northern Heavens, we must come back to the Sun, which we have left behind us. The Earth revolves round him in a year, and in consequence he seems to revolve round us, sweeping through a vast circle of the celestial sphere. In each year, at the same period, he passes the same points of the Heavens, in front of the same constellations, which are rendered invisible by his light. We know that the stars are at a fixed position from the Earth, whatever their distance, and that if we do not see them at noon as at midnight, it is simply because they are extinguished by the dazzling light of the orb of day. With the aid of a telescope it is always possible to see the more brilliant of them. The Zodiac is the zone of stars traversed by the Sun in the course of a year. This word is derived from the Greek Zodiakos, which signifies "animal," and this etymology arose because most of the figures traced[Pg 43] on this belt of stars represent animals. The belt is divided into twelve parts that are called the twelve Signs of the Zodiac, also named by the ancients the "Houses of the Sun," since the Sun visits one of them in each month. These are the signs, with the primitive characters that distinguish them: the Ram ♈, the Bull ♉, the Twins ♊, the Crab ♋, the Lion ♌, the Virgin ♍, the Balance ♎, the Scorpion ♏, the Archer ♐, the Goat ♑, the Water-Carrier ♒, the Fishes ♓. The sign ♈ Aries represents the horns of the Ram, ♉ the head of the Bull, and so on. If you will now follow me into the Houses of the Sun you will readily recognize them again, provided you have a clear picture of the principal stars of the Northern Heavens. First, you see the Ram, the initial sign of the Zodiac; because at the epoch at which the actual Zodiac was fixed, the Sun entered this sign at the vernal equinox, and the equator crossed the ecliptic at this point. This constellation, in which the horns of the Ram (third magnitude) are the brightest, is situated between Andromeda and the Pleiades. Two thousand years ago, the Ram was regarded as the symbol of spring; but owing to the secular movement of the precession of the equinoxes, the Sun is no longer there on March 21: he is in the Fishes. To the left, or east of the Ram, we find the Bull,[Pg 44] the head of which forms a triangle in which burns Aldebaran, of first magnitude, a magnificent red star that marks the right eye; and the Hyades, scintillating pale and trembling, on its forehead. The timid Pleiades, as we have seen, veil themselves on the shoulder of the Bull—a captivating cluster, of which six stars can be counted with the unaided eye, while several hundred are discovered with the telescope. Next the Twins. They are easily recognized by the two fine stars, α and β, of first magnitude, which mark their heads, and immortalize Castor and Pollux, the sons of Jupiter, celebrated for their indissoluble friendship. Cancer, the Crab, is the least important sign of the Zodiac. It is distinguished only by five stars of fourth and fifth magnitudes, situated below the line of Castor and Pollux, and by a pale cluster called Præsepe, the Beehive. The Lion next approaches, superb in his majesty. At his heart is a gorgeous star of first magnitude, α or Regulus. This figure forms a grand trapezium of four stars on the celestial sphere. The Virgin exhibits a splendid star of first magnitude; this is Spica, which with Regulus and Arcturus, form a triangle by which this constellation can be recognized. [Pg 45] The Balance follows the Virgin. Its scales, marked by two stars of second magnitude, are situated a little to the East of Spica. We next come to the eighth constellation of the Zodiac, which is one of the most beautiful of this belt of stars. Antares, a red star of first magnitude, occupies the heart of the venomous and accursed Scorpion. It is situated on the prolongation of a line joining Regulus to Spica, and forms with Vega of the Lyre, and Arcturus of the Herdsman, a great isosceles triangle, of which this latter star is the apex. The Scorpion, held to be a sign of ill luck, has been prejudicial to the Archer, which follows it, and traces an oblique trapezium in the sky, a little to the east of Antares. These two southernmost constellations never rise much above the horizon for France and England. In fable, the Archer is Chiron, the preceptor of Jason, Achilles and Æsculapius. Capricorn lies to the south of Altaïr, on the prolongation of a line from the Lyre to the Eagle. It is hardly noticeable save for the stars α and β of third magnitude, which scintillate on its forehead. The Water-Carrier pours his streams toward the horizon. He is not rich in stars, exhibiting only three of third magnitude that form a very flattened triangle. Lastly the Fishes, concluding sign of the Zodiac, are[Pg 46] found to the south of Andromeda and Pegasus. Save for α, of third magnitude, this constellation consists of small stars that are hardly visible. These twelve zodiacal constellations will be recognized on examining the chart (Figs. 10–11). We must now visit the stars of the Southern Heavens, some of which are equally deserving of admiration. Fig. 10.—The Constellations of the Zodiac: summer and autumn; Capricorn, Archer, Scorpion, Balance, Virgin, Lion. It should in the first place be noted that the signs of the Zodiac and the Southern Constellations are not, like those which are circumpolar, perpetually visible at all periods of the year. Their visibility depends on the time of year and the hour of the night.[4] In order to admire the fine constellations of the North, as described above, we have only to open our[Pg 47] windows on a clear summer's evening, or walk round the garden in the mysterious light of these inaccessible suns, while we look up at the immense fields in which each star is like the head of a celestial spear. But the summer is over, autumn is upon us, and then, too soon, comes winter clothed in hoar-frost. The days are short and cold, dark and dreary; but as a compensation the night is much longer, and adorns herself with her most beautiful jewels, offering us the contemplation of her inexhaustible treasures. Fig. 11.—The Constellations of the Zodiac: winter and spring; Crab, Twins, Bull, Ram, Fishes, Water-Carrier. First, let us do homage to the magnificent Orion, most splendid of all the constellations: he advances like a colossal giant, and confronts the Bull. This constellation appears about midnight in November, in the south-eastern Heavens; toward eleven[Pg 48] o'clock in December and January, due south; about ten in February, in the south-east; about nine in March, and about eight in April, in the west; and then sets below our horizon. Fig. 12.—Orion and his celestial companions. It is indisputably the most striking figure in the sky, and with the Great Bear, the most ancient in history, the first that was noticed: both are referred to in the ancient texts of China, Chaldea, and Egypt. [Pg 49] Eight principal stars delineate its outline; two are of the first magnitude, five of the second, and one of