I. STAR CHART OF THE PRINCIPAL CONSTELLATIONS
I. STAR CHART OF THE PRINCIPAL CONSTELLATIONS
Large illustrations (all less than 100 kB):Plate 1,Plate 2,Plate 3,Plate 4,Plate 5,Plate 6,Plate 7,Plate 8
Low in the southwest is a bright red star called Antares, or α Scorpionis.
The space between Sagittarius and Hercules and Scorpio is occupied by the Serpent (Serpens) and the Serpent-bearer, or Ophiuchus (Plates 6 and 7). The head of the Serpent is near the Crown, and marked by a small triangle. The head of Ophiuchus is close to the head of Hercules, and may be known by a star of the second magnitude. Each shoulder is marked by a pair of stars. His feet are near the Scorpion.
Nearly on a line with Arcturus and γ Ursæ Majoris (Plate 1), and rather nearer the latter, is an isolated star of the third magnitude, called Cor Caroli, or Charles’ Heart. This is the only prominent star in the constellation of Canes Venatici, or the Hunting Dogs.
Cassiopeia is almost due east of the Pole Star. A line drawn from the latter through β Cassiopeiæ[26]and prolonged, passes through two stars of the second and third magnitude. These, with two others farther to the south, form a large square, called the Square of Pegasus. Three of these, as seen by the chart (Plate 5), belong to the constellation Pegasus, or the Winged Horse. α Pegasi is called Markab, and β is called Algenib. The bright stars in the neck and nose can be found by the chart.
II. STAR CHART OF THE PRINCIPAL CONSTELLATIONS
II. STAR CHART OF THE PRINCIPAL CONSTELLATIONS
Large illustrations (all less than 100 kB):Plate 9,Plate 10,Plate 11,Plate 12,Plate 13,Plate 14,Plate 15,Plate 16
The fourth star in the Square of Pegasus belongs (Plate 8) to the constellation Andromeda. Nearly in a line with α Pegasi and this star are two other bright stars belonging to Andromeda. The stars in her belt may be found by the chart.
Following the direction of the line of stars in Andromeda just mentioned, and bending a little towards the east, we come to Algol, or β Persei, a remarkable variable star. This star may be readily recognized from the fact, together with β and γ Andromeda and the four stars in the Square of Pegasus, it forms a figure similar in outline to the Dipper in Ursa Major, but much larger. If the handle of this great Dipper is made straight instead of being bent, the star in the end of it is α[27]Persei, of the second magnitude. This star has one of the third magnitude on each side of it. The other stars in Perseus may be found by the chart.
Just below θ in the head of Pegasus (Plate 9) are three stars of the third and fourth magnitudes, forming a small arc. These mark the urn of Aquarius, the Water-bearer. His body consists of a trapezium of four stars of the third and fourth magnitudes. Small clusters of stars show the course of the water flowing from his urn.
This stream enters the mouth of the Southern Fish, or Piscis Australis. The only bright star in this constellation is Fomalhaut, which is of the first magnitude, and at this time will be low down in the southeast.
To the south of Aquarius is Capricornus, or the Goat. He is marked by three pairs of stars arranged in a triangle. One pair is in his head, another in his tail, and the third in his knees.
Near Altair (Plate 5), and a little higher up, is a small diamond of stars forming the Dolphin, or Delphinus.
A little to the west of the Dolphin, in the Milky Way, are four stars of the fourth magnitude, which form the constellation Sagitta, or the Arrow.
Constellations Visible in October.If we look at the heavens at eight o’clock on the 15th of October, we shall see that all the constellations described above have shifted somewhat towards the west. Arcturus and Antares have set. In the east, below Andromeda (Plate 10), we see a pair of bright stars, which are the only conspicuous ones in the constellation Aries, or the Ram.
About half-way between Aries and γ Andromedæ are three stars which form a small triangle. This constellation is called Triangulum, or the Triangle.
Between Aries and Pegasus is the constellation Pisces, or the Fishes. The southernmost Fish may be recognized by a pentagon of small stars lying below the back of Pegasus. There are no conspicuous stars in the other Fish, which is directly below Andromeda.
Constellations Visible in November.At eight o’clock in the evening on the 15th of November, we see at a glance that the constellations with which we have become acquainted have moved yet farther to the westward. Boötes, the Crown, Ophiuchus, and the Archer have set; Pegasus, Cassiopeia, and Andromeda are overhead; while new constellations appear in the east.
We notice at once (Plate 11) a very bright star in the northeast, directly below Perseus. This is Capella, or α Aurigæ. There are five other conspicuous stars in Auriga, or the Charioteer; and with Capella they form an irregular pentagon.
Somewhat to the eastward (Plate 12), and a little lower down, is a very bright red star. This is Aldebaran, or α Tauri. It is familiarly known as the Bull’s eye. It will be noticed by the map that it is at one end of a V which forms the face of the Bull. This group is known as the Hyades. Somewhat above the Hyades is a smaller group, called the Pleiades,—more commonly known as the Seven Stars, though few persons can distinguish more than six. The bright star on the northern horn, or β Tauri, is also in the foot of Auriga, and counts as γ of that constellation.
All the space between Taurus and the Southern Fish, and below Aries and Pisces (Plate 13), is occupied by Cetus, the Whale. The head is marked by a triangle of rather conspicuous stars below Aries; the tail, by a bright star of the second magnitude, which is now just about as far above the horizon as Fomalhaut. On the body there are five stars, forming a sort of sickle. About halfway between this sickle and the triangle, in the head, is σ Ceti, which is also called Mira, or the wonderful star.
Constellations Visible in December.At eight o’clock in the evening in the middle of December, we shall find that Hercules, Aquila, and Capricornus have sunk below the horizon; while Vega and the Swan are on the point of setting. The Great Bear is climbing up in the northeast. In the east we behold by far the most brilliant group of constellations we have yet seen. Capella and Aldebaran are now high up; and below the former (Plate 12) is the splendid constellation of Orion. His belt, made up of three stars in a straight line, will be recognized at once. Above this, on one shoulder, is a star of the first magnitude, called Betelgeuse, or α Orionis. About as far from the belt, on the other side, is another star of the first magnitude, called Rigel. There are two other fainter stars which form a large trapezium with Betelgeuse and Rigel. The three small stars below the belt are upon the sword.
Below Orion (Plate 14) is a small trapezium of stars which are in the constellation of Lepus, or the Hare. The head is marked by a small triangle, as seen on the map.
To the north of Orion, and a little lower down (Plate 12), are two bright stars near together, one of the first and the other of the second magnitude. The latter is called Castor, and the former Pollux. These stars are in the constellation of Gemini, or the Twins. A line of three smaller stars just in the edge of the Milky Way marks the feet, and another line of three the knees. Pollux forms a large triangle with Capella and Betelgeuse.
Constellations Visible in January.At eight in the evening on the 15th of January, Vega, Altair, the Dolphin, Aquarius, and Fomalhaut have disappeared in the west; Deneb and the Square of Pegasus are near the horizon; while Capella and Aldebaran are nearly overhead. Two stars of exceeding brilliancy have come up in the west. The one farthest to the south (Plate 14) is the brightest star in the whole heavens. It is called Sirius, or the Dogstar; and is in the constellation of Canis Major, or the Great Dog, which can be readily traced by the lines on the map.
The other bright star is between Sirius and Pollux (Plate 12), and is called Procyon. It is in Canis Minor, or the Little Dog. The only other prominent star in this constellation is one of the third magnitude near Procyon.
Procyon, Sirius, and Betelgeuse form a large equilateral triangle.
Orion and the group of constellations about it constitute by far the most brilliant portion of the heavens, as seen in our latitude. There are, in all, only about twenty stars of the first magnitude, and seven of these are in this immediate vicinity.
Constellations Visible in February.If we look at the heavens at the same time in the evening about the middle of February, we shall miss Cygnus and Pegasus from the west. Auriga and Orion are nearly overhead.
Southeast of the Great Bear (Plate 15) is a red star of the first magnitude, called Regulus, in the[28]constellation of Leo, or the Lion. There are five stars near Regulus, which together with it form a group often called the Sickle. The star in the tail is Denebola, which makes a right-angled triangle with two others near it.
MAP SHOWING THE LOCATIONS OF NORTHERN CONSTELLATIONS
MAP SHOWING THE LOCATIONS OF NORTHERN CONSTELLATIONS
Large illustration(363 kB)
Between Leo and Gemini is the constellation Cancer, or the Crab. It contains no bright stars, but a remarkable cluster of small stars called Præsepe, or the Beehive.
Below Regulus (Plate 14) is a bright red star of the second magnitude, called Cor Hydræ, or the Hydra’s Heart. The head of Hydra is marked by five small stars. The coils of the monster can be traced by the map. A portion of the constellation is onPlate 16.
Constellations Visible in March.At the middle of March, the heavens will have shifted round somewhat towards the west; but all the conspicuous constellations of the preceding month are still visible, while no new ones at all brilliant have come into view.
If we draw a line from the end of the Great Bear’s tail to Denebola, it will pass through two constellations,—Canes Venatici, described above; and Coma Berenices, or Berenice’s Hair, a large cluster of faint stars. (Plate 15).
MAP SHOWING THE LOCATIONS OF THE SOUTHERN CONSTELLATIONS AND ALSO MANY REMARKABLE NEBULAR FORMS1. Double nebula in Gemini. 2. Double nebula of great brilliancy in Coma Berenicis. 3. Small double nebula. 4. Curiously shaped nebula in Ophiuchus. 5. Two nebulous spots in Canes Venatici. 6. Remarkable veil-like nebula in Lyra. 7. Elliptical nebula in Perseus. 8. Nebulous spot in Sagittarius, split into three pieces; a double star in center. 9. Large curiously-shaped nebula in Rober Caroli, filled with minute stars. 10. Great nebula in Andromeda, visible to the eye. 11. Nebula in Cetus. 12. Elongated nebula in Cygnus. 13. Brilliant round spots in Sagittarius. 14. Round spots in Andromeda. 15-16. Spots in Orion and Ursa Major. 17. Most remarkable of all nebula, in Orion. 18. Great oval nebula in Vulpes, containing two darker nebulae. 19. Nebulous figure in Canis Venaticus. 20. Nebular clouds in the Southern hemisphere.
MAP SHOWING THE LOCATIONS OF THE SOUTHERN CONSTELLATIONS AND ALSO MANY REMARKABLE NEBULAR FORMS
1. Double nebula in Gemini. 2. Double nebula of great brilliancy in Coma Berenicis. 3. Small double nebula. 4. Curiously shaped nebula in Ophiuchus. 5. Two nebulous spots in Canes Venatici. 6. Remarkable veil-like nebula in Lyra. 7. Elliptical nebula in Perseus. 8. Nebulous spot in Sagittarius, split into three pieces; a double star in center. 9. Large curiously-shaped nebula in Rober Caroli, filled with minute stars. 10. Great nebula in Andromeda, visible to the eye. 11. Nebula in Cetus. 12. Elongated nebula in Cygnus. 13. Brilliant round spots in Sagittarius. 14. Round spots in Andromeda. 15-16. Spots in Orion and Ursa Major. 17. Most remarkable of all nebula, in Orion. 18. Great oval nebula in Vulpes, containing two darker nebulae. 19. Nebulous figure in Canis Venaticus. 20. Nebular clouds in the Southern hemisphere.
Large illustration(497 kB)
Constellations Visible in April.At the middle of April, Aries and Andromeda have set; Taurus, Orion and Canis Major are sinking towards the west; the Great Bear and the Lion are overhead; Arcturus has risen in the northeast (Plate 16); and some way to the south of this is seen a star of the first magnitude, which forms a large triangle with Arcturus and Denebola. It is called Spica[30]Virginis, and is the chief star in the constellation Virgo, or the Virgin. The stars on the breast and wings can be found with the aid of the map.
South of Virgo is a trapezium of four stars, which are in the constellation of Corvus, or the Crow.
Constellations Visible in May.At the middle of May, Taurus, Orion, and Canis Major have set; Vega has just come up in the northeast; and between Vega and Arcturus we again see Hercules and Corona. Below Spica are two stars of the second magnitude, belonging to the constellation Libra, or the Balance. Another star of the fourth magnitude forms a triangle with these, and marks one pan of the balance. (Plate 7).
Constellations Visible in June.In June we shall find that Canis Minor, Perseus, Auriga, and Gemini have either set, or are on the point of setting; Arcturus is overhead; Cygnus and Aquila are just rising. Ophiuchus is well up; and low in the southeast we see again the red star Antares, in the constellation Scorpio, or the Scorpion (Plate 6). There is a star of the third magnitude on each side of Antares, and several stars of the third and fourth magnitudes in the head and claws. The configuration of these stars is much like a boy’s kite with a long tail. Scorpio is a very brilliant constellation, and is seen to better advantage in July and August.
Constellations Visible in July and August. We have now described all the important constellations visible in our latitude. Those which are seen in July and August are mainly those described under the last two or three months, and under September.
Southern Circumpolar Constellations. There are a number of constellations near the South Pole of the heavens which never rise in our latitude, just as there are certain ones near the North Pole which never set. These are called the southern circumpolar constellations.
CONSTELLATIONS VISIBLE EACH MONTH
The following table gives the constellations visible at eight o’clock in the evening about the middle of each month. The stars opposite the names of the constellations indicate those visible in the month designated at the top.
Everyone knows the Milky Way. It is one of the most striking sights of a clear night, for only on clear, moonless nights can we see its cloudy track of light across the heavens. More than any other celestial object it affects us with a sense of mystery and of unknown destiny as, indeed, it has affected men at all times and in all countries. To the American Indian it was the “path of souls.” In ancient mythology it had various meanings: thus, it was the highway of the gods to Olympus; or it sprang from the ears of corn dropped by Isis as she fled from her pursuer; or it marked the original course of the sun, which he later abandoned. In mediæval times it became associated by pilgrims with their own journeys.
It stretches like a vast ragged semicircle over the sky. Indeed, it traces a rough circle, for this line is continued over the southern hemisphere also. The circle is, however, very far from being smooth or even; the path is full of irregularities. It varies in width to an extent of about thirty degrees, and varies also considerably in brightness. Its total area has been estimated to cover rather less than one-fourth of the whole northern hemisphere of the sky, and to cover about one-third of the southern hemisphere. Its track lies through the constellations Cassiopeia and Auriga; it passes between the feet of Gemini and the horns of Taurus, through Orion just above the giant’s club, and through the neck and shoulder of Monoceros. It passes above Sirius into Argo, here entering the southern hemisphere, and through Argo and the Southern Cross into the Centaur. In the Centaur the Milky Way divides into two streams, in a manner which suggests the divided course of a river around an island, a dark rift between the two luminous streams representing the island.
It is a very long island, however, for the double conformation of the Milky Way extends over one-third of its entire course—that is to say, one hundred and twenty degrees of the circle. The divergent branches reunite in the northern hemisphere in the constellation Cygnus. The brighter stream passes through Norma, Ara, Scorpio and Sagittarius; along the bow of Sagittarius into Antinous, here entering the northern hemisphere again; then through Aquila, Sagitta, and Vulpecula it arrives at Cygnus and reunion with the branch which left it in Centaur. From Cygnus the stream, now single, passes through Lacerta and the head of Cepheus to the point whence we started, in Cassiopeia.
As we follow the Milky Way throughout its course, we find it continually sending out streaming appendages of nebulous appearance towards clusters, nebulæ, or groups of stars. In Norma it sends out a complicated series of nebulous streaks and patches, covering the Scorpion’s tail, spreading faintly over the leg of Ophiuchus, and extending beyond, as if to meet a corresponding branch sent off from the region of Cygnus in the northern hemisphere. The latter is a very bright and remarkable streak, running south through Cygnus and Aquila, to become lost in a dim and sparsely starred region. From Cassiopeia a vivid branch proceeds to the chief star of Perseus, and faint streaks appear to continue the “feeler” towards the Hyades and the Pleiades. There are many other “feelers” of the same kind, and they are all of great interest, because they seem to show some sort of influence exercised by the Milky Way upon the whole starry universe.
Ancient and Modern Conceptions of the Nature of the Milky Way.Strange theories as to the nature of the Milky Way have been put forward at various times. Anaxagoras thought it might be due to the shadow of our globe; Aristotle, that it was some kind of mist due to the exhalation of vapors from the earth.
But a grander and truer conception of its nature and situation, removed far from the earth and independent of any terrestrial cause, had early come to several minds. Pythagoras and Democritus both formed the conjecture that its shimmer might be due to innumerable stars, and Galileo’s telescope confirmed their theory.
As we have seen, the Milky Way is by no means a simple stream of stars; with careful observation, even the naked eye can perceive something of its irregular detail, when the atmosphere is unusually clear, and there is no moon. Viewed under these conditions through a good telescope, the effect of the Milky Way, when made to pass progressively before the vision, is one of unexampled grandeur and sublimity.
THE STARRY GRANDEUR OF THE MILKY WAY
COURSE OF THE MILKY WAY THROUGH THE TWO HEMISPHERES OF THE HEAVENSThese two drawings show the two semi-circles of the Milky Way as they extend from the regions of the Polar Star to the region of the Southern Cross on each side of the apparent sphere of the heavens. It will be noticed that the bright stars congregate near its region, and that there is a characteristic harmony in the way in which the wisps appear to project into space, suggesting some common cause for this appearance throughout the whole galaxy.
COURSE OF THE MILKY WAY THROUGH THE TWO HEMISPHERES OF THE HEAVENS
These two drawings show the two semi-circles of the Milky Way as they extend from the regions of the Polar Star to the region of the Southern Cross on each side of the apparent sphere of the heavens. It will be noticed that the bright stars congregate near its region, and that there is a characteristic harmony in the way in which the wisps appear to project into space, suggesting some common cause for this appearance throughout the whole galaxy.
Large illustration(235 kB)
The general effect has been well likened to that of an old, gnarled tree-trunk, marked with knots and curving lines, and riddled with dark holes and passages, linked together by shimmering wisps or arches. This general effect is practically lost as the detail becomes clear in a telescopic view. The detail is extremely various. At one point it may consist of separate stars scattered irregularly upon a background of darkness; at another, of star-clusters, sometimes following one upon another in long, processional line; at another, the stars seem to collect in small, soft clouds, presenting the appearance, as the telescope sweeps over them, of drifting foam.
The Strange, Dark Rifts in the Skyscape Where No Stars Appear.At yet another point the track may be involved in nebulosity in which many stars appear to be imbedded. Perhaps the most characteristic features are several which have already been remarked as conspicuous in star-clusters or nebulæ, such as lines of stars, dark lanes or rifts, and dark holes. The lines of stars, which are evidently connected by some actual physical relation, are either straight, curved, radiated, or in parallels. In Sagittarius is a very striking collection of about thirty stars resembling in form a forked twig with a curved hook at the unforked end. The dark rifts in the Milky Way show the same features as those in star-clusters. Sometimes they are parallel; sometimes they radiate like branches from a common center; sometimes they are lines with bright stars; sometimes they are quite black, as if utterly void; sometimes slightly luminous, as if powdered with small stars.
It can be by no accident or chance that in the vast edifice of the heavens objects of certain classes should crowd into the belt of the Milky Way, and other classes avoid it; it points to the whole forming a single growth, an essential unity. For there is but one belt in the heavens, like the Milky Way, a belt in which small stars, new stars, and planetary nebulæ find their favorite home; and that belt encircles the entire heavens; and similarly that belt is the only region from which the white nebulæ appear to be repelled. The Milky Way forms the foundation, the strong and buttressed wall of the celestial building; the white nebulæ close in the roof of its dome.
It has already been observed that a number of stars are arranged in clusters of groups, while others, like our own sun, are at vast distances from their nearest neighbors. Some of these clusters, of which the Pleiades afford the best example to the naked eye, can be resolved by a keen eye into separate stars; some, like Præsepe in Cancer, which only show to the naked eye as a hazy spot of light, break up in a good field-glass into clusters of stars; but the majority of stellar clusters require a powerful telescope for their resolution.
It was long ago noticed that, the more powerful a telescope was, the greater was the number of these hazy spots of light which it would resolve into clusters of stars. Consequently the opinion was formed that all the hazy little clouds or nebulæ which are so prevalent throughout a large part of the sky were simply clusters of stars, so far away that their light merged into a single impression on the eye. A great number of these nebulæ were only resolved by large telescopes; many were found to be irresolvable by any telescope. It was simply concluded from this that they were still more distant than the clusters which had yielded to the resolving powers of the telescope; and it was further supposed that each of these clusters of stars might be a separate universe or galaxy, comparable in extent and importance with our own universe, bounded by the vast girdle of the Milky Way.
The Nebular Hypothesis.This grand conception of innumerable universes scattered throughout space was speedily destroyed by the spectroscope, which distinguishes with entire certainty between the light sent to us from a solid star and that emitted by a gas. When it was turned upon the nebulæ which had been supposed in reality to be star-clusters so distant that no telescope could resolve them, it showed unmistakably that these nebulæ were not star-groups, but simply masses of incandescent gas.
Besides, nebulæ vary greatly in form and appearance; some are clearly clusters of stars, others are perfectly hazy. A round or oval form is sometimes exhibited, with a gradual condensation towards the center, and a number of stars standing in the center of a nebulous haze can be observed. Such observations on nebulæ caused Kant and Laplace to suggest a theory—now known as the nebular theory—as to the formation of worlds. They considered that the solar system, for example, originally existed as uncondensed nebulous matter. This gradually condensed towards the center, forming the nucleus of the sun, and later the outer parts separated into distinct parts, each part condensing into a planet. The different forms of nebulæ observed in the heavens are then supposed to be systems in different stages of development.
Many of the stars shine with colored light, as red, blue, green, or yellow.
These colors are exhibited in striking contrast in many of the double stars. Combinations of blue and yellow, or green and yellow, are not uncommon; while in fewer cases we find one star white and the other purple, or one white and the other red. In several instances each star has a rosy light.
The following are a few of the most interesting colored double stars:
Single stars of a fiery red or deep orange color are common enough. Of the first color may be mentioned Aldebaran, Antares and Betelgeuse. Arcturus is a good example of an orange star. Isolated stars of a deep blue or green color are very rarely found; among the conspicuous stars, β Libræ appears to be the only instance.
It is now a well-established fact that the stars change their color. Sirius was described as a fiery red star by the ancients, is now decided green color.
NAMES OF IMPORTANT STARSINCLUDING THOSE OF FIRST MAGNITUDE
When the earth is between the moon and the sun in a line, the moon lies in the shadow of the earth, and so suffers temporary obscuration; alunar eclipsethen takes place. When the moon passes between the earth and the sun, the latter is at certain places on the earth obscured by the dark body of the moon, and asolar eclipsetakes place.
Lunar Eclipses.The shadow cast by the earth is conical, and may be shown to extend about one million miles from its surface. At a distance of a quarter of a million miles away the width of this shadow is about six thousand miles; and if the moon passes into it at that approximate distance from the earth, its disc of two thousand miles diameter may be partially or totally obscured. The moon and sun may be on opposite sides of the earth, and yet the former not in shadow. This is due to the fact that the moon’s orbit round the earth is not exactly in the same plane as that of the earth’s orbit round the sun. If it were so, we should have total eclipses at every full moon; but since the two planes are inclined to each other at an angle of 5° 9′, eclipses will occur when the moon is at or near itsnodesor positions of coincidence with the plane of the ecliptic. Partial eclipses are produced when only a portion of the moon passes into shadow; annular eclipses such as are sometimes observed in the case of the sun cannot occur with the moon.
GIANT SHADOWS CAST BY THE EARTH AND MOON