Astronomy for Amateurs Part 5

One of the most splendid of these _double stars_, and at the same time one of the easiest to perceive, is [zeta] in the Great Bear, or Mizar, mentioned above in describing this constellation. It has no contrasting colors, but exactly resembles twin diamonds of the finest water, which fascinate the gaze, even through a small objective.

Its components are of the second and fourth magnitudes, their distance = 14"[6]. Some idea of their appearance in a small telescope may be obtained from the subjoined figure (Fig. 17).

Another very brilliant pair is Castor. Magnitudes second and third.

Distance 5.6"". Very easy to observe. [gamma] in the Virgin resolves into two splendid diamonds of third magnitude. Distance, 5.0". Another double star is [gamma] of the Ram, of fourth magnitude. Distance, 8.9".

[Ill.u.s.tration: FIG. 17.--The double star Mizar.]

And here are two that are even more curious by reason of their coloring: [gamma] in Andromeda, composed of a fine orange star, and one emerald-green, which again is accompanied by a tiny comrade of the deepest blue. This group in a good telescope is most attractive.

Magnitudes, second and fifth. Distance, 10".

[beta] of the Swan, or Albireo, referred to in the last chapter, has been a.n.a.lyzed into two stars: one golden-yellow, the other sapphire.

Magnitudes, third and fifth. Distance, 34". [alpha] of the Greyhounds, known also as the Heart of Charles II, is golden-yellow and lilac.

Magnitudes, third and fifth. Distance 20".[7]

[alpha] of Hercules revolves a splendid emerald and a ruby in the skies; [zeta] of the Lyre exhibits a yellow and a green star; Rigel, an electric sun, and a small sapphire; Antares is ruddy and emerald-green; [eta] of Perseus resolves into a burning red star, and one smaller that is deep blue, and so on.

These exquisite double stars revolve in gracious and splendid couples around one another, as in some majestic valse, marrying their multi-colored fires in the midst of the starry firmament.

Here, we constantly receive a pure and dazzling white light from our burning luminary. Its ray, indeed, contains the potentiality of every conceivable color, but picture the fantastic illumination of the worlds that gravitate round these multiple and colored suns as they shed floods of blue and roseate, red, or orange light around them! What a fairy spectacle must life present upon these distant universes!

Let us suppose that we inhabit a planet illuminated by two suns, one blue, the other red.

It is morning. The sapphire sun climbs slowly up the Heavens, coloring the atmosphere with a somber and almost melancholy hue. The blue disk attains the zenith, and is beginning its descent toward the West, when the East lights up with the flames of a scarlet sun, which in its turn ascends the heights of the firmament. The West is plunged in the penumbra of the rays of the blue sun, while the East is illuminated with the purple and burning rays of the ruby orb.

The first sun is setting when the second noon shines for the inhabitants of this strange world. But the red sun, too, accomplishes the law of its destiny. Hardly has it disappeared in the conflagration of its last rays, with which the West is flushed, when the blue orb reappears on the opposite side, shedding a pale azure light upon the world it illuminates, which knows no night. And thus these two suns fraternize in the Heavens over the common task of renewing a thousand effects of extra-terrestrial light for the globes that are subject to their variations.

Scarlet, indigo, green, and golden suns; pearly and multi-colored Moons; are these not fairy visions, dazzling to our poor sight, condemned while here below to see and know but one white Sun?

As we have learned, there are not only double, but triple, and also multiple stars. One of the finest ternary systems is that of [gamma] in Andromeda, above mentioned. Its large star is orange, its second green, its third blue, but the two last are in close juxtaposition, and a powerful telescope is needed to separate them. A triple star more easy to observe is [zeta] of Cancer, composed of three orbs of fifth magnitude, at a distance of 1" and 5"; the first two revolve round their common center of gravity in fifty-nine years, the third takes over three hundred years. The preceding figure shows this system in a fairly powerful objective (Fig. 18).

[Ill.u.s.tration: FIG. 18.--Triple star [zeta] in Cancer.]

In the Lyre, a little above the dazzling Vega, [epsilon] is of fourth magnitude, which seems a little elongated to the unaided eye, and can even be a.n.a.lyzed into two contiguous stars by very sharp sight. But on examining this attractive pair with a small gla.s.s, it is further obvious that each of these stars is double; so that they form a splendid quadruple system of two couples (Fig. 19): one of fifth and a half and sixth magnitudes, at a distance of 2.4", the other of sixth and seventh, 3.2" distant. The distance between the two pairs is 207".

[Ill.u.s.tration: FIG. 19.--Quadruple star [epsilon] of the Lyre.]

In speaking of Orion, we referred to the marvelous star [theta] situated in the no less famous Nebula, below the Belt; this star forms a dazzling s.e.xtuple system, in the very heart of the nebula (Fig. 20). How different to our Sun, sailing through s.p.a.ce in modest isolation!

Be it noted that all these stars are animated by prodigious motions that impel them in every direction.

[Ill.u.s.tration: FIG. 20.--s.e.xtuple star [theta] in the Nebula of Orion.]

There are no fixed stars. On every side throughout Infinity, the burning suns--enormous globes, blazing centers of light and heat--are flying at giddy speed toward an unknown goal, traversing millions of miles each day, crossing century by century such vast s.p.a.ces as are inconceivable to the human intellect.

If the stars appear motionless to us, it is because they are so remote, their secular movements being only manifested on the celestial sphere by imperceptible displacements. But in reality these suns are in perpetual commotion in the abysses of the Heavens, which they quicken with an extraordinary animation.

These perpetual and c.u.mulative motions must eventually modify the aspect of the Constellations: but these changes will only take effect very slowly; and for thousands and thousands of years longer the heroes and heroines of mythology will keep their respective places in the Heavens, and reign undisturbed beneath the starry vault.

Examination of these star motions reveals the fact that our Sun is plunging with all his system (the Earth included) toward the Constellation of Hercules. We are changing our position every moment: in an hour we shall be 70,000 kilometers (43,500 miles) farther than we are at present. The Sun and the Earth will never again traverse the s.p.a.ce they have just left, and which they have deserted forever.

And here let us pause for an instant to consider the _variable stars_.

Our Sun, which is constant and uniform in its light, does not set the type of all the stars. A great number of them are variable--either periodically, in regular cycles--or irregularly.

We are already acquainted with the variations of Algol, in Perseus, due to its partial eclipse by a dark globe gravitating in the line of our vision. There are several others of the same type: these are not, properly speaking, variable stars. But there are many others the intrinsic light of which undergoes actual variations.

In order to realize this, let us imagine that our Earth belongs to such a sun, for example, to a star in the southern constellation of the Whale, indicated by the letter [omicron], which has been named the "wonderful" (Mira Ceti). Our new sun is shining to-day with a dazzling light, shedding the gladness of his joyous beams upon nature and in our hearts. For two months we admire the superb orb, sparkling in the azure illuminated with its radiance. Then of a sudden, its light fades, and diminishes in intensity, though the sky remains clear. Imperceptibly, our fine sun darkens; the atmosphere becomes sad and dull, there is an antic.i.p.ation of universal death. For five long months our world is plunged in a kind of penumbra; all nature is saddened in the general woe.

But while we are bewailing the cruelty of our lot, our cherished luminary revives. The intensity of its light increases slowly. Its brilliancy augments, and finally, at the end of three months, it has recovered its former splendors, and showers its bright beams upon our world, flooding it with joy. But--we must not rejoice too quickly! This splendid blaze will not endure. The flaming star will pale once more; fade back to its minimum; and then again revive. Such is the nature of this capricious sun. It varies in three hundred and thirty-one days, and from yellow at the maximum, turns red at the minimum. This star, Mira Ceti, which is one of the most curious of its type, varies from the second to the ninth magnitudes: we cite it as one example; hundreds of others might be instanced.

Thus the sky is no black curtain dotted with brilliant points, no empty desert, silent and monotonous. It is a prodigious theater on which the most fantastic plays are continually being acted. Only--there are no spectators.

Again, we must note the _temporary stars_, which shine for a certain time, and then die out rapidly. Such was the star in Ca.s.siopeia, in 1572, the light of which exceeded Sirius in its visibility in full daylight, burning for five months with unparalleled splendor, dominating all other stars of first magnitude; after which it died out gradually, disappearing at the end of seventeen months, to the terror of the peoples, who saw in it the harbinger of the world's end: that of 1604, in the Constellation of the Serpent, which shone for a year; of 1866, of second magnitude, in the Northern Crown, which appeared for a few weeks only; of 1876, in the Swan; of 1885, in the Nebula of Andromeda; of 1891, in the Charioteer; and quite recently, of 1901, in Perseus.

These temporary stars, which appear spontaneously to the observers on the Earth, and quickly vanish again, are doubtless due to collisions, conflagrations, or celestial cataclysms. But we only see them long after the epoch at which the phenomena occurred, years upon years, and centuries ago. For instance, the conflagration photographed by the author in 1901, in Perseus, must have occurred in the time of Queen Elizabeth. It has taken all this time for the rays of light to reach us.

The Heavens are full of surprises, on which we can bestow but a fleeting glance within these limits. They present a field of infinite variety.

Who has not noticed the Milky Way, the pale belt that traverses the entire firmament and is so luminous on clear evenings in the Constellations of the Swan and the Lyre? It is indeed a swarm of stars.

Each is individually too small to excite our retina, but as a whole, curiously enough, they are perfectly visible. With opera-gla.s.ses we divine the starry const.i.tution: a small telescope shows us marvels.

Eighteen millions of stars were counted there with the gauges of William Herschel.

Now this Milky Way is a symbol, not of the Universe, but of the Universes that succeed each other through the vast s.p.a.ces to Infinity.

Our Sun is a star of the Milky Way. It surrounds us like a great circle, and if the Earth were transparent, we should see it pa.s.s beneath our feet as well as over our heads. It consists of a very considerable ma.s.s of star-cl.u.s.ters, varying greatly in extent and number, some projected in front of others, while the whole forms an agglomeration.

[Ill.u.s.tration: FIG. 21.--The Star-Cl.u.s.ter in Hercules.]

Among this ma.s.s of star-groups, several thousands of which are already known to us, we will select one of the most curious, the Cl.u.s.ter in Hercules, which can be distinguished with the unaided eye, between the stars [eta] and [zeta] of that constellation. Many photographs of it have been taken in the author's observatory at Juvisy, showing some thousands of stars; and one of these is reproduced in the accompanying figure (Fig. 21). Is it not a veritable universe?

[Ill.u.s.tration: FIG. 22.--The Star-Cl.u.s.ter in the Centaur.]

Another of the most beautiful, on account of its regularity, is that of the Centaur (Fig. 22).

These groups often a.s.sume the most extraordinary shapes in the telescope, such as crowns, fishes, crabs, open mouths, birds with outspread wings, etc.

We must also note the _gaseous nebulae_, universes in the making, _e.g._, the famous Nebula in Orion, of which we obtained some notion a while ago in connection with its s.e.xtuple star: and also that in Andromeda (Fig. 23).

[Ill.u.s.tration: FIG. 23.--The Nebula in Andromeda.]

[Ill.u.s.tration: FIG. 24.--Nebula in the Greyhounds.]

Perhaps the most marvelous of all is that of the Greyhounds, which evolves in gigantic spirals round a dazzling focus, and then loses itself far off in the recesses of s.p.a.ce. Fig. 24 gives a picture of it.