Astronomy for Amateurs Part 4

19. Fomalhaut, or [alpha] of the Southern Fish.

THE STARS OF THE SECOND MAGNITUDE

Then come the stars of the second magnitude, of which there are fifty-nine. The stars of the Great Bear (with the exception of [delta], which is of third magnitude), the Pole-Star, the chief stars in Orion (after Rigel and Betelgeuse), of the Lion, of Pegasus, of Andromeda, of Ca.s.siopeia, are of this order. These, with the former, const.i.tute the princ.i.p.al outlines of the constellations visible to us.

Then follow the third and fourth magnitudes, and so on.

The following table gives a summary of the series, down to the sixth magnitude, which is the limit of visibility for the unaided human eye:

19 stars of first magnitude.

59 of second magnitude.

182 of third magnitude.

530 of fourth magnitude.

1,600 of fifth magnitude.

4,800 of sixth magnitude.

This makes a total of some seven thousand stars visible to the unaided eye. It will be seen that each series is, roughly speaking, three times as populated as that preceding it; consequently, if we multiply the number of any cla.s.s by three, we obtain the approximate number of stars that make up the cla.s.s succeeding it.

Seven thousand stars! It is an imposing figure, when one reflects that all these lucid points are suns, as enormous as they are potent, as incandescent as our own (which exceeds the volume of the Earth by more than a million times), distant centers of light and heat, exerting their attraction on unknown systems. And yet it is generally imagined that millions of stars are visible in the firmament. This is an illusion; even the best vision is unable to distinguish stars below the sixth magnitude, and ordinary sight is far from discovering all of these.

Again, seven thousand stars for the whole Heavens makes only three thousand five hundred for half the sky. And we can only see one celestial hemisphere at a time. Moreover, toward the horizon, the vapor of the atmosphere veils the little stars of sixth magnitude. In reality, we never see at a given moment more than three thousand stars. This number is below that of the population of a small town.

But celestial s.p.a.ce is unlimited, and we must not suppose that these seven thousand stars that fascinate our eyes and enrich our Heavens, without which our nights would be black, dark, and empty,[5] comprise the whole of Creation. They only represent the vestibule of the temple.

Where our vision is arrested, a larger, more powerful eye, that is developing from century to century, plunges its a.n.a.lyzing gaze into the abysses, and reflects back to the insatiable curiosity of science the light of the innumerable suns that it discovers. This eye is the lens of the optical instruments. Even opera-gla.s.ses disclose stars of the seventh magnitude. A small astronomical objective penetrates to the eighth and ninth orders. More powerful instruments attain the tenth.

The Heavens are progressively transformed to the eye of the astronomer, and soon he is able to reckon hundreds of thousands of orbs in the night. The evolution continues, the power of the instrument is developed; and the stars of the eleventh and twelfth magnitudes are discovered successively, and together number four millions. Then follow the thirteenth, fourteenth, and fifteenth magnitudes. This is the sequence:

7th magnitude 13,000.

8th " 40,000.

9th " 120,000.

10th " 380,000.

11th " 1,000,000.

12th " 3,000,000.

13th " 9,000,000.

14th " 27,000,000.

15th " 80,000,000.

Accordingly, the most powerful telescopes of the day, reenforced by celestial photography, can bring a stream of more than 120 millions of stars into the scope of our vision.

The photographic map of the Heavens now being executed comprises the first fourteen magnitudes, and will give the precise position of some 40,000,000 stars, distributed over 22,054 sheets, forming a sphere 3 meters 44 centimeters in diameter.

The boldest imagination is overwhelmed by these figures, and fails to picture such millions of suns--formidable and burning globes that roll through s.p.a.ce, sweeping their systems along with them. What furnaces are there! what unknown lives! what vast immensities!

And again, what enormous distances must separate the stars, to admit of their free revolution in the ether! In what abysses, at what a distance from our terrestrial atom, must these magnificent and dazzling Suns pursue the paths traced for them by Destiny!

If all the stars radiated an equal light, their distances might be calculated on the principle that an object appears smaller in proportion to its distance. But this equality does not exist. The suns were not all cast in the same mold.

Indeed, the stars differ widely in size and brightness, and the distances that have been measured show that the most brilliant are not the nearest. They are scattered through s.p.a.ce at all distances.

Among the nearer stars of which it has been found possible to calculate the distance, some are found to be of the fourth, fifth, sixth, seventh, eighth, and even ninth magnitudes, proving that the most brilliant are not always the least distant.

For the rest, among the beautiful and s.h.i.+ning stars with which we made acquaintance in the last chapter may be cited Sirius, which at a distance of 92 trillion kilometers (57 trillion miles) from here still dazzles us with its burning fires; Procyon or [alpha] of the Little Dog, as remote as 112 trillion kilometers (69-1/2 trillion miles); Altar of the Eagle, at 160 trillion kilometers (99 trillion miles); the white Vega, at 204 trillion kilometers (126-1/2 trillion miles); Capella, at 276 trillion kilometers (171 trillion miles); and the Pole-Star at 344 trillion kilometers (213-1/2 trillion miles). The light that flies through s.p.a.ce at a velocity of 300,000 kilometers (186,000 miles) per second, takes thirty-six years and a half to reach us from this distant sun: _i.e._, the luminous ray we are now receiving from Polaris has been traveling for more than the third of a century. When you, gentle reader, were born, the ray that arrives to-day from the Pole-Star was already speeding on its way. In the first second after it had started it traveled 300,000 kilometers; in the second it added another 300,000 which at once makes 600,000 kilometers; add another 300,000 kilometers for the third second, and so on during the thirty-six years and a half.

If we tried to arrange the number 300,000 (which represents the distance accomplished in one second) in superposed rows, as if for an addition sum, as many times as is necessary to obtain the distance that separates the Pole-Star from our Earth, the necessary operation would comprise 1,151,064,000 rows, and the sheet of paper required for the setting out of such a sum would measure approximately 11,510 kilometers (about 7,000 miles), _i.e._, almost the diameter of our terrestrial globe, or about four times the distance from Paris to Moscow!

Is it not impossible to realize that our Sun, with its entire system, is lost in the Heavens at such a distance from his peers in s.p.a.ce? At the distance of the least remote of the stars he would appear as one of the smallest.

The nearest star to us is [alpha] of the Centaur, of first magnitude, a neighbor of the South Pole, invisible in our lat.i.tudes. Its distance is 275,000 radii of the terrestrial orbit, _i.e._, 275,000 times 149 million kilometers, which gives 41 trillions, or 41,000 milliards of kilometers (= 25-1/2 trillion miles). [A milliard = 1,000 millions, the French billion. A trillion = 1,000 milliards, or a million millions, the English billion. The _French_ nomenclature has been retained by the translator.] At a speed of 300,000 kilometers (186,000 miles) per second the light takes four years to come from thence. It is a fine double star.

The next nearest star after this is a little orb invisible to the unaided eye. It has no name, and stands as No. 21,185 in the Catalogue of Lalande. It almost attains the seventh magnitude (6.8). Its distance is 64 trillion kilometers (39-1/2 trillion miles).

The third of which the distance has been measured is the small star in Cygnus, already referred to in Chapter II, in describing the Constellations. Its distance is 69 trillion kilometers (42-1/2 trillion miles). This, too, is a double star. The light takes seven years to reach us.

As we have seen, the fine stars Sirius, Procyon, Aldebaran, Altar, Vega, and Capella are more remote.

Our solar system is thus very isolated in the vastness of Infinitude.

The latest known planet of our system, Neptune, performs its revolutions in s.p.a.ce at 4 milliards, 470 million kilometers (2,771,400,000 miles) from our Sun. Even this is a respectable distance! But beyond this world, an immense gulf, almost a void abyss, extends to the nearest star, [alpha] of the Centaur. Between Neptune and Centauris there is no star to cheer the black and cold solitude of the immense vacuum. One or two unknown planets, some wandering comets, and swarms of meteors, doubtless traverse those unknown s.p.a.ces, but all invisible to us.

Later on we will discuss the methods that have been employed in measuring these distances. Let us now continue our description.

Now that we have some notion of the distance of the stars we must approach them with the telescope, and compare them one with another.

Let us, for example, get close to Sirius: in this star we admire a sun that is several times heavier than our own, and of much greater ma.s.s, accompanied by a second sun that revolves round it in fifty years. Its light is exceedingly white, and it notably burns with hydrogen flames, like Vega and Altar.

Now let us approach Arcturus, Capella, Aldebaran: these are yellow stars with golden rays, like our Sun, and the vapor of iron, of sodium, and of many other metals can be identified in their spectrum. These stars are older than the first, and the ruddy ones, such as Antares, Betelgeuse, [alpha] of Hercules, are still older; several of them are variable, and are on their way to final extinction.

The Heavens afford us a perennial store of treasure, wherein the thinker, poet or artist can find inexhaustible subjects of contemplation.

You have heard of the celestial jewels, the diamonds, rubies, emeralds, sapphires, topazes, and other precious stones of the sidereal casket.

These marvels are met with especially among the double stars.

Our Sun, white and solitary, gives no idea of the real aspect of some of its brothers in Infinitude. There are as many different types as there are suns!

Stars, you will think, are like individuals: each has its distinct characteristics: no two are comparable. And indeed this reflection is justified. While human vanity does homage to Phoebus, divine King of the Heavens, other suns of still greater magnificence form groups of two or three splendid orbs, which roll the prodigious combinations of their double, triple, or multiple systems through s.p.a.ce, pouring on to the worlds that accompany them a flood of changing light, now blue, now red, now violet, etc.

In the inexhaustible variety of Creation there exist Suns that are united in pairs, bound by a common destiny, cradled in the same attraction, and often colored in the most delicate and entrancing shades conceivable. Here will be a dazzling ruby, its glowing color shedding joy; there a deep blue sapphire of tender tone; beyond, the finest emeralds, hue of hope. Diamonds of translucent purity and whiteness sparkle from the abyss, and shed their penetrating light into the vast s.p.a.ce. What splendors are scattered broadcast over the sky! what profusion!

To the naked eye, the groups appear like ordinary stars, mere luminous points of greater or less brilliancy; but the telescope soon discovers the beauty of these systems; the star is duplicated into two distinct suns, in close proximity. These groups of two or several suns are not merely due to an effect of perspective--_i.e._, the presence of two or more stars in our line of sight; as a rule they const.i.tute real physical systems, and these suns, a.s.sociated in a common lot, rotate round one another in a more or less rapid period, that varies for each system.