Читать книгу The Circle of Knowledge: A Classified, Simplified, Visualized Book of Answers - Various - Страница 39

In beginning our study of the stars, let us put ourselves in the position of the earliest observers. Let us first, like them, watch the stars, and see how they appear from night to night.

We see, at the first glance, that the stars vary much in brightness. The brightest ones—like Sirius, Capella, Arcturus, and Vega—are called stars of the first magnitude. Those less brilliant, like the six brightest of “the Dipper,” are said to be of the second magnitude. All the stars which can be seen with the unaided eye are thus divided into six classes or magnitudes, according to their brightness.

Constellations. We also see that the stars are not uniformly distributed over the sky. They seem to be arranged in groups, some of which take the form of familiar objects. Every one knows the seven bright stars which are called “the Dipper.” Another group resembles a sickle, another a cross, and so on. All the stars in the heavens have been divided into groups called constellations. Many of these were recognized and named at a very early period.

We should become familiar with these constellations in order to study the stars with any profit.

It is necessary, in the first place, to have some way of designating the stars in each constellation. Many of the brighter stars have proper names as Sirius, Arcturus, and Vega; but the great majority of them are marked by the letters of the Greek alphabet. The brightest star in each constellation is called α (alpha); the next brightest, β (beta); the next, γ (gamma); and so on. The characters and names of the Greek alphabet are as follows:

α,	Alpha.
β,	Beta.
γ,	Gamma.
δ,	Delta.
ε,	Epsilon.
ζ,	Zeta.
η,	Eta.
θ,	Theta.
ι,	Iota.
κ,	Kappa.
λ,	Lambda.
μ,	Mu.
ν,	Nu.
ξ,	Xi.
ο,	Omicron.
π,	Pi.
ρ,	Rho.
σ,	Sigma.
τ,	Tau.
υ,	Upsilon.
φ,	Phi.
χ,	Chi.
ψ,	Psi.
ω,	Omega.

These letters are followed by the Latin name of the constellation. Thus Aldebaran is called α Tauri; Rigel, β Orionis; Sirius, α Canis Majoris.

If there are more stars in a constellation than can be named from the Greek alphabet, the Roman alphabet is used in the same way; and when both alphabets are exhausted, numbers are used.

Circumpolar Constellations. One of the most important constellations, and one easily recognized, is the Great Bear, or Ursa Major. It is represented in Plate 1 on the Star Chart. It may be known by the seven stars forming “the Dipper.” The Bear’s feet are marked by three pairs of stars. These and the star in the nose can be readily found by means of the lines drawn on the chart. It may be remarked here, that in all cases the stars thus connected by lines are the leading stars of the constellation. The stars α and β are called the Pointers. If a line be drawn from β to α, and prolonged about five times the distance between them, it will pass near an isolated star of the second magnitude known as the Pole Star, or Polaris. This is the brightest star in the Little Bear, or Ursa Minor (Plate 2). It is in the end of the handle of a second “dipper,” smaller than the one in the Great Bear.

On the opposite side of the Pole Star from the Great Bear, and at about the same distance, is another conspicuous constellation, called Cassiopeia. Its five brightest stars form an irregular W, opening towards the Pole Star (Plate 2).

About half-way between the two Dippers three stars of the third magnitude will be seen, the only stars at all prominent in that neighborhood. These belong to Draco, or the Dragon. The chart will show that the other stars in the body of the monster form an irregular curve around the Little Bear, while the head is marked by four stars arranged in a trapezium. Two of these stars, β and γ, are quite bright. A little less than half-way from Cassiopeia to the head of the Dragon is a constellation known as Cepheus, five stars of which form an irregular K.

These five constellations never set in our latitude, and are called circumpolar constellations.

Constellations Visible in September. At this time the Great Bear will be low down in the northwest, and the Dragon’s head nearly in the zenith. If we draw a line from ζ to η of the Great Bear and prolong it, we shall find that it will pass near a reddish star of the first magnitude. This star is called Arcturus, or α Boötis, since it is the brightest star in the constellation Boötes. Of its other conspicuous stars, four form a cross. These and the remaining stars of the constellation can be readily traced with the aid of Plate 3.

Near the Dragon’s head (Plate 4) may be seen a very bright star of the first magnitude, shining with a pure white light. This star is Vega, or α Lyræ.

If we draw a line from Arcturus to Vega (Plate 3), it will pass through two constellations, the Crown, or Corona Borealis and Hercules. The former is about one-third of the way from Arcturus to Vega, and consists of a semicircle of six stars, the brightest of which is called Alphecca or Gemma Coronæ—“the gem of the crown.”

Hercules is about half-way between the Crown and Vega. This constellation is marked by a trapezoid of stars of the third magnitude. A star in one foot is near the Dragon’s head; there is also a star in each shoulder, and one in the face.

Just across the Milky Way from Vega (Plate 5) is a star of the first magnitude, called Altair, or α Aquilæ. This star marks the constellation Aquila, or the Eagle, and may be recognized by a small star on each side of it. These are the only important stars in this constellation.

In the Milky Way, between Altair and Cassiopeia (Plate 4), there is a large constellation called Cygnus, or the Swan. Six of its stars form a large cross, by which it will be readily known. α Cygni is often called Deneb. It forms a large isosceles triangle with Altair and Vega.

Low down in the south, on the edge of the Milky Way (Plate 6), is a constellation called Sagittarius, or the Archer. It may be known by [25] five stars forming an inverted dipper, often called “the Milk-dipper.” The head is marked by a small triangle. The other stars, as seen by the map, may be grouped so as to represent a bow and an arrow.

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

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.