THE STARS OF SUMMER.
Let us now suppose that the Earth has advanced for three months in its
orbit since we studied the stars of spring, and that, in consequence,
the heavens have made one quarter of an apparent revolution. Then we
shall find that the stars which in spring shone above the western
horizon have been carried down out of sight, while the constellations
that were then in the east have now climbed to the zenith, or passed
over to the west, and a fresh set of stars has taken their place in the
east. In the present chapter we shall deal with what may be called the
stars of summer; and, in order to furnish occupation for the observer
with an opera-glass throughout the summer months, I have endeavored to
so choose the constellations in which our explorations will be made,
that some of them shall be favorably situated in each of the months of
June, July, and August. The circular map represents the heavens at
midnight on the 1st of June; at eleven o'clock, on the 15th of June; at
ten o'clock, on the 1st of July; at nine o'clock, on the 15th of July;
and at eight o'clock, on the 1st of August. Remembering that the center
of the map is the point over his head, and that the edge of it
represents the circle of the horizon, the reader, by a little attention
and comparison with the sky, will be able to fix in his mind the
relative situation of the various constellations. The maps that follow
will show him these constellations on a larger scale, and give him the
names of their chief stars.
[Illustration: MAP 7.]
The observer need not wait until midnight on the 1st of June in order to
find some of the constellations included in our map. Earlier in the
evening, at about that date, say at nine o'clock, he will be able to see
many of these constellations, but he must look for them farther toward
the east than they are represented in the map. The bright stars in
Booetes and Virgo, for instance, instead of being over in the southwest,
as in the map, will be near the meridian; while Lyra, instead of shining
high overhead, will be found climbing up out of the northeast. It would
be well to begin at nine o'clock, about the 1st of June, and watch the
motions of the heavens for two or three hours. At the commencement of
the observations you will find the stars in Booetes, Virgo, and Lyra in
the positions I have just mentioned, while half-way down the western sky
will be seen the Sickle of Leo. The brilliant Procyon and Capella will
be found almost ready to set in the west and northwest, respectively.
Between Procyon and Capella, and higher above the horizon, shine the
twin stars in Gemini.
In an hour Procyon, Capella, and the Twins will be setting, and Spica
will be well past the meridian. In another hour the observer will
perceive that the constellations are approaching the places given to
them in our map, and at midnight he will find them all in their assigned
positions. A single evening spent in observations of this sort will
teach him more about the places of the stars than he could learn from a
dozen books.
Taking, now, the largest opera-glass you can get (I have before said
that the diameter of the object-glasses should not be less than 1.5
inch, and, I may add, the larger they are the better), find the
constellation Scorpio, and its chief star Antares. The map shows you
where to look for it at midnight on the 1st of June. If you prefer to
begin at nine o'clock at that date, then, instead of looking directly in
the south for Scorpio, you must expect to see it just rising in the
southeast. You will recognize Antares by its fiery color, as well as by
the striking arrangement of its surrounding stars. There are few
constellations which bear so close a resemblance to the objects they are
named after as Scorpio. It does not require a very violent exercise of
the imagination to see in this long, winding trail of stars a gigantic
scorpion, with its head to the west, and flourishing its upraised sting
that glitters with a pair of twin stars, as if ready to strike. Readers
of the old story of Phaeton's disastrous attempt to drive the chariot of
the Sun for a day will remember it was the sight of this threatening
monster that so terrified the ambitious youth as he dashed along the
Zodiac, that he lost control of Apollo's horses, and came near burning
the earth up by running the Sun into it.
Antares rather gains in redness when viewed with a glass. Its color is
very remarkable, and it is a curious circumstance that with powerful
telescopes a small, bright-green star is seen apparently almost touching
it. Antares belongs to Secchi's third type of suns, that in which the
spectroscopic appearances suggest the existence of a powerfully
absorptive atmosphere, and which are believed on various grounds to be,
as Lockyer has said, "in the last visible stage of cooling"; in other
words, almost extinct. This great, red star probably in actual size
exceeds our sun, and no one can help feeling the sublime nature of those
studies which give us reason to think that here we can actually behold
almost the expiring throes of a giant brother of our giant sun. Only,
the lifetime of a sun is many millions of years, and its gradual
extinction, even after it has reached a stage as advanced as that of
Antares is supposed to be, may occupy a longer time than the whole
duration of the human race.
A little close inspection with the naked eye will show three fifth- or
sixth-magnitude stars above Antares and Sigma ([sigma]), which form,
with those stars, the figure of an irregular pentagon. An opera-glass
shows this figure very plainly. The nearest of these stars to Antares,
the one directly above it, is known by the number 22, and belongs to
Scorpio, while the farthest away, which marks the northernmost corner of
the pentagon, is Rho in Ophiuchus. Try a powerful field-glass upon the
two stars just named. Take 22 first. You will without much difficulty
perceive that it has a little star under its wing, below and to the
right, and more than twice as far away above it there is another faint
star. Then turn to Rho. Look sharp and you will catch sight of two
companion stars, one close to Rho on the right and a little below, and
the other still closer and directly above Rho. The latter is quite
difficult to be seen distinctly, but the sight is a very pretty one.
The opera-glass will show a number of faint stars scattered around
Antares. Turn now to Beta ([beta]) in Scorpio, with the glass. A very
pretty pair of stars will be seen hanging below [beta]. Sweeping
downward from this point to the horizon you will find many beautiful
star-fields. The star marked Nu ([nu]) is a double which you will be
able to separate with a powerful field-glass, the distance between its
components being 40".
[Illustration: MAP 8.]
And next let us look at a star-cluster. You will see on Map No. 8 an
object marked 4 M, near Antares. Its designation means that it is No. 4
in Messier's catalogue of nebulae. It is not a true nebula, but a closely
compacted cluster of stars. With the opera-glass, if you are looking in
a clear and moonless night, you will see it as a curious nebulous speck.
With a field-glass its real nature is more apparent, and it is seen to
blaze brighter toward the center. It is, in fact, one of those universes
within the universe where thousands of suns are associated together by
some unknown law of aggregation into assemblages of whose splendor the
slight view that we can get gives us but the faintest conception.
The object above and to the right of Antares, marked in the map 80 M.,
is a nebula, and although the nebula itself is too small to be seen with
an opera-glass (a field-glass shows it as a mere wisp of light), yet
there is a pretty array of small stars in its neighborhood worth looking
at. Besides, this nebula is of special interest, because in 1860 a star
suddenly took its place. At least, that is what seemed to have happened.
What really did occur, probably, was that a variable or temporary star,
situated between us and the nebula, and ordinarily too faint to be
perceived, received a sudden and enormous accession of light, and blazed
up so brightly as to blot out of sight the faint nebula behind it. If
this star should make its appearance again, it could easily be seen with
an opera-glass, and so it will not be useless for the reader to know
where to look for it. The quarter of the heavens with which we are now
dealing is famous for these celestial conflagrations, if so they may be
called. The first temporary star of which there is any record appeared
in the constellation of the Scorpion, near the head, 134 years before
Christ. It must have been a most extraordinary phenomenon, for it
attracted attention all over the world, and both Greek and Chinese
annals contain descriptions of it. In 393 A. D. a temporary star shone
out in the tail of Scorpio. In 827 A. D. Arabian astronomers, under the
Caliph Al-Mamoun, the son of Haroun-al-Raschid, who broke into the great
pyramid, observed a temporary star, that shone for four months in the
constellation of the Scorpion. In 1203 there was a temporary star, of a
bluish color, in the tail of Scorpio, and in 1578 another in the head of
the constellation. Besides these there are records of the appearance of
four temporary stars in the neighboring constellation of Ophiuchus, one
of which, that of 1604, is very famous, and will be described later on.
It is conceivable that these strange outbursts in and near Scorpio may
have had some effect in causing this constellation to be regarded by the
ancients as malign in its influence.
We shall presently see some examples of star-clusters and nebulae with
which the instruments we are using are better capable of dealing than
with the one described above. In the mean time, let us follow the
bending row of stars from Antares toward the south and east. When you
reach the star Mu ([mu]), you are not unlikely to stop with an
exclamation of admiration, for the glass will separate it into two stars
that, shining side by side, seem trying to rival each other in
brightness. But the next star below [mu], marked Zeta ([zeta]), is even
more beautiful. It also separates into two stars, one being reddish and
the other bluish in color. The contrast in a clear night is very
pleasing. But this is not all. Above the two stars you will notice a
curious nebulous speck. Now, if you have a powerful field-glass, here is
an opportunity to view one of the prettiest sights in the heavens. The
field-glass not only makes the two stars appear brighter, and their
colors more pronounced, but it shows a third, fainter star below them,
making a small triangle, and brings other still fainter stars into
sight, while the nebulous speck above turns into a charmingly beautiful
little star-cluster, whose components are so close that their rays are
inextricably mingled in a maze of light. This little cut is an attempt
to represent the scene, but no engraving can reproduce the life and
sparkle of it.
[Illustration: ZETA SCORPIONIS.]
Following the bend of the Scorpion's tail upward, we come to the pair of
stars in the sting. These, of course, are thrown wide apart by the
opera-glass. Then let us sweep off to the eastward a little way and find
the cluster known as 7 M. You will see it marked on the map. Above it,
and near enough to be included in the same field of view, is 6 M., a
smaller cluster. Both of these have a sparkling appearance with an
opera-glass, and by close attention some of the separate stars in 7 M.
may be detected. With a field-glass these clusters become much more
striking and starry looking, and the curious radiated structure of 7 M.
comes out.
In looking at such objects we can not too often recall to our minds the
significance of what we see--that these glimmering specks are the lights
in the windows of the universe which carry to us, across inconceivable
tracts of space, the assurance that we and our little system are not
alone in the heavens; that all around us, and even on the very confines
of immensity, Nature is busy, as she is here, and the laws of light,
heat, gravitation (and why not of life?), are in full activity.
The clusters we have just been looking at lie on the borders of Scorpio
and Sagittarius. Let us cross over into the latter constellation, which
commemorates the centaur Chiron. We are now in another, and even a
richer, region of wonders. The Milky-Way, streaming down out of the
northeast, pours, in a luminous flood, through Sagittarius, inundating
that whole region of the heavens with seeming deeps and shallows, and
finally bursting the barriers of the horizon disappears, only to glow
with redoubled splendor in the southern hemisphere. The stars Zeta
([zeta]), Tau ([tau]), Sigma ([sigma]), Phi ([phi]), Lambda ([lambda]),
and Mu ([mu]) indicate the outlines of a figure sometimes called the
Milk-Dipper, which is very evident when the eye has once recognized it.
On either side of the upturned handle of this dipper-like figure lie
some of the most interesting objects in the sky. Let us take the star
[mu] for a starting-point. Sweep downward and to the right a little
way, and you will be startled by a most singular phenomenon that has
suddenly made its appearance in the field of view of your glass. You
may, perhaps, be tempted to congratulate yourself on having got ahead of
all the astronomers, and discovered a comet. It is really a combination
of a star-cluster with a nebula, and is known as 8 M. Sir John Herschel
has described the "nebulous folds and masses" and dark oval gaps which
he saw in this nebula with his large telescope at the Cape of Good Hope.
But no telescope is needed to make it appear a wonderful object; an
opera-glass suffices for that, and a field-glass reveals still more of
its marvelous structure.
The reader will recollect that we found the summer solstice close to a
wonderful star-swarm in the feet of Gemini. Singularly enough the winter
solstice is also near a star-cluster. It is to be found near a line
drawn from 8 M. to the star [mu] Sagittarii, and about one third of the
way from the cluster to the star. There is another less conspicuous
star-cluster still closer to the solstitial point here, for this part of
the heavens teems with such aggregations.
On the opposite side of the star [mu]--that is to say, above and a
little to the left--is an entirely different but almost equally
attractive spectacle, the swarm of stars called 24 M. Here, again, the
field-glass easily shows its superiority over the opera-glass, for
magnifying power is needed to bring out the innumerable little twinklers
of which the cluster is composed. But, whether you use an opera-glass or
a field-glass, do not fail to gaze long and steadily at this island of
stars, for much of its beauty becomes evident only after the eye has
accustomed itself to disentangle the glimmering rays with which the
whole field of view is filled. Try the method of averted vision, and
hundreds of the finest conceivable points of light will seem to spring
into view out of the depths of the sky. The necessity of a perfectly
clear night, and the absence of moonlight, can not be too much insisted
upon for observations such as these. Everybody knows how the moonlight
blots out the smaller stars. A slight haziness, or smoke, in the air
produces a similar effect. It is as important to the observer with an
opera-glass to have a transparent atmosphere as it is to one who would
use a telescope; but, fortunately, the work of the former is not so much
interfered with by currents of air. Always avoid the neighborhood of any
bright light. Electric lights in particular are an abomination to
star-gazers.
The cloud of stars we have just been looking at is in a very rich region
of the Milky-Way, in the little modern constellation called "Sobieski's
Shield," which we have not named upon our map. Sweeping slowly upward
from 24 M. a little way with the field-glass, we will pass in succession
over three nebulous-looking spots. The second of these, counting upward,
is the famous Horseshoe nebula. Its wonders are beyond the reach of our
instrument, but its place may be recognized. Look carefully all around
this region, and you will perceive that the old gods, who traveled this
road (the Milky-Way was sometimes called the pathway of the gods), trod
upon golden sands. Off a little way to the east you will find the rich
cluster called 25 M. But do not imagine the thousands of stars that your
opera-glass or field-glass reveals comprise all the riches of this
Golconda of the heavens. You might ply the powers of the greatest
telescope in a vain attempt to exhaust its wealth. As a hint of the
wonders that lie hidden here, let me quote Father Secchi's description
of a starry spot in this same neighborhood, viewed with the great
telescope at Rome. After telling of "beds of stars superposed upon one
another," and of the wonderful geometrical arrangement of the larger
stars visible in the field, he adds:
"The greater number are arranged in spiral arcs, in which one can count
as many as ten or twelve stars of the ninth to the tenth magnitude
following one another in a curve, like beads upon a string. Sometimes
they form rays which seem to diverge from a common focus, and, what is
very singular, one usually finds, either at the center of the rays, or
at the beginning of the curve, a more brilliant star of a red color,
which seems to lead the march. It is impossible to believe that such an
arrangement can be accidental."
The reader will recall the somewhat similar description that Admiral
Smyth and Mr. Webb have given of a star-cluster in Gemini (see Chapter
I).
The milky look of the background of the Galaxy is, of course, caused by
the intermingled radiations of inconceivably minute and inconceivably
numerous stars, thousands of which become separately visible, the number
thus distinguishable varying with the size of the instrument. But the
most powerful telescope yet placed in human hands can not sound these
starry deeps to the bottom. The evidence given by Prof. Holden, the
Director of the Lick Observatory, on this point is very interesting.
Speaking of the performance of the gigantic telescope on Mount Hamilton,
thirty-six inches in aperture, he says:
"The Milky-Way is a wonderful sight, and I have been much interested to
see that there is, even with our superlative power, no final resolution
of its finer parts into stars. There is always the background of
unresolved nebulosity on which hundreds and thousands of stars are
studded--each a bright, sharp, separate point."
The groups of stars forming the eastern half of the constellation of
Sagittarius are worth sweeping over with the glass, as a number of
pretty pairs may be found there.
Sagittarius stands in the old star-maps as a centaur,
half-horse-half-man, facing the west, with drawn bow, and
arrow pointed at the Scorpion.
[Illustration: MAP 9.]
Next let us pass to the double constellation adjoining Scorpio and
Sagittarius on the north--Ophiuchus and the Serpent. These
constellations, as our map shows, are curiously intermixed. The
imagination of the old star-gazers, who named them, saw here the figure
of a giant grasping a writhing serpent with his hands. The head of the
serpent is under the Northern Crown, and its tail ends over the
star-gemmed region that we have just described, called "Sobieski's
Shield." Ophiuchus stands, as figured in Flamsteed's "Atlas," upon the
back of the Scorpion, holding the serpent with one hand below the neck,
this hand being indicated by the pair of stars marked Epsilon
([epsilon]) and Delta ([delta]), and with the other near the tail. The
stars Tau ([tau]) and Nu ([nu]) indicate the second hand. The giant's
face is toward the observer, and the star Alpha ([alpha]), also called
Ras Alhague, shines in his forehead, while Beta ([beta]) and Gamma
([gamma]) mark his right shoulder. Ophiuchus has been held to represent
the famous physician AEsculapius. One may well repress the tendency to
smile at these fanciful legends when he reflects upon their antiquity.
There is no doubt that this double constellation is at least three
thousand years old--that is to say, for thirty centuries the imagination
of men has continued to shape these stars into the figures of a gigantic
man struggling with a huge serpent. If it possesses no other interest,
then it at least has that which attaches to all things ancient. Like
many other of the constellations it has proved longer-lived than the
mightiest nations. While Greece flourished and decayed, while Rome rose
and fell, while the scepter of civilization has passed from race to
race, these starry creations of fancy have shone on unchanged. The mind
that would ignore them now deserves compassion.
The reader will observe a little circle in the map, and near it the
figures 1604. This indicates the spot where one of the most famous
temporary stars on record appeared in the year 1604. At first it was far
brighter than any other star in the heavens; but it quickly faded, and
in a little over a year disappeared. It is particularly interesting,
because Kepler--the quaintest, and not far from the greatest, figure in
astronomical history--wrote a curious book about it. Some of the
philosophers of the day argued that the sudden outburst of the wonderful
star was caused by the chance meeting of atoms. Kepler's reply was
characteristic, as well as amusing:
"I will tell those disputants, my opponents, not my own opinion, but my
wife's. Yesterday, when I was weary with writing, my mind being quite
dusty with considering these atoms, I was called to supper, and a salad
I had asked for was set before me. 'It seems, then,' said I, aloud,
'that if pewter dishes, leaves of lettuce, grains of salt, drops of
water, vinegar and oil, and slices of egg, had been flying about in the
air from all eternity, it might at last happen by chance that there
would come a salad.' 'Yes,' says my wife, 'but not so nice and
well-dressed as this of mine is.'"
While there are no objects of special interest for the observer with an
opera-glass in Ophiuchus, he will find it worth while to sweep over it
for what he may pick up, and, in particular, he should look at the group
of stars southeast of [beta] and [gamma]. These stars have been shaped
into a little modern asterism called Taurus Poniatowskii, and it will be
noticed that five of them mark the outlines of a letter V, resembling
the well-known figure of the Hyades.
Also look at the stars in the head of Serpens, several of which form a
figure like a letter [X]. A little west of Theta ([theta]) in the tail
of Serpens, is a beautiful swarm of little stars, upon which a
field-glass may be used with advantage. The star [theta] is itself a
charming double, just within the separating power of a very powerful
field-glass under favorable circumstances, the component stars being
only about one third of a minute apart.
Do not fail to notice the remarkable subdivisions of the Milky-Way in
this neighborhood. Its current seems divided into numerous channels and
bays, interspersed with gaps that might be likened to islands, and the
star [theta] appears to be situated upon one of these islands of the
galaxy. This complicated structure of the Milky-Way extends downward to
the horizon, and upward through the constellation Cygnus, and of its
phenomenal appearance in that region we shall have more to say further
on.
Directly north of Ophiuchus is the constellation Hercules, interesting
as occupying that part of the heavens toward which the proper motion of
the sun is bearing the earth and its fellow-planets, at the rate,
probably, of not less than 160,000,000 miles in a year--a stupendous
voyage through space, of whose destination we are as ignorant as the
crew of a ship sailing under sealed orders, and, like whom, we must
depend upon such inferences as we can draw from courses and distances,
for no other information comes to us from the flagship of our squadron.
[Illustration: MAP 10.]
In the accompanying map we have represented the beautiful constellations
Lyra and the Northern Crown, lying on either side of Hercules. The
reader should note that the point overhead in this map is not far from
the star Eta ([eta]) in Hercules. The bottom of the map is toward the
south, the right-hand side is west, and the left-hand side east. It is
important to keep these directions in mind, in comparing the map with
the sky. For instance, the observer must not expect to look into the
south and see Hercules half-way up the sky, with Lyra a little east of
it; he must look for Hercules nearly overhead, and Lyra a little east
of the zenith. The same precautions are not necessary in using the maps
of Scorpio, Sagittarius, and Ophiuchus, because those constellations are
nearer the horizon, and so the observer does not have to imagine the map
as being suspended over his head.
The name Hercules sufficiently indicates the mythological origin of the
constellation, and yet the Greeks did not know it by that name, for
Aratus calls it "the Phantom whose name none can tell." The Northern
Crown, according to fable, was the celebrated crown of Ariadne, and Lyra
was the harp of Orpheus himself, with whose sweet music he charmed the
hosts of Hades, and persuaded Pluto to yield up to him his lost
Eurydice.
With the aid of the map you will be able to recognize the principal
stars and star-groups in Hercules, and will find many interesting
combinations of stars for yourself. An object of special interest is the
celebrated star-cluster 13 M. You will find it on the map between the
stars Eta ([eta]) and Zeta ([zeta]). While an opera-glass will only show
it as a faint and minute speck, lying nearly between two little stars,
it is nevertheless well worth looking for, on account of the great
renown of this wonderful congregation of stars. Sir William Herschel
computed the number of stars contained in it as about fourteen thousand.
It is roughly spherical in shape, though there are many straggling stars
around it evidently connected with the cluster. In short, it is _a ball
of suns_. The reader should not mistake what that implies, however.
These suns, though truly solar bodies, are probably very much smaller
than our sun. Mr. Gore has computed their average diameter to be
forty-five thousand miles, and the distance separating each from the
next to be 9,000,000,000 miles. It may not be uninteresting to inquire
what would be the appearance of the sky to dwellers within such a system
of suns. Adopting Mr. Gore's estimates, and supposing 9,000,000,000
miles to be very nearly the uniform distance apart of the stars in the
cluster, and forty-five thousand miles their uniform diameter, then,
starting with a single star in the center, their arrangement might be
approximately in concentric spherical shells, situated about
9,000,000,000 miles apart. The first shell, counting outward from the
center, would contain a dozen stars, each of which, as seen by an
observer stationed upon a planet at the center of the cluster, would
shine eleven hundred times as bright as Sirius appears to us. The number
of the stars in each shell would increase as they receded from the
center in proportion to the squares of the radii of the successive
shells, while their luminosity, as seen from the center, would vary
inversely as those squares. Still, the outermost stars--the total number
being limited to fourteen or fifteen thousand--would appear to our
observer at the center of the system about five times as brilliant as
Sirius.
It is clear, then, that he would be dwelling in a sort of perpetual
daylight. His planet might receive from the particular sun around which
it revolved as brilliant a daylight as our sun gives to us, but let us
see what would be the illumination of its night side. Adopting Zoellner's
estimate of the light of the sun as 618,000 times as great as that of
the full moon, and choosing among the various estimates of the light of
Sirius as compared with the sun 1/4000000000 as probably the nearest
the truth, we find that the moon sends us about sixty-five hundred times
as much light as Sirius does. Now, since the dozen stars nearest the
center of the cluster would each appear to our observer eleven hundred
times as bright as Sirius, all of them together would give a little more
than twice as much light as the full moon sheds upon the earth. But as
only half the stars in the cluster would be above the horizon at once we
must diminish this estimate by one half, in order to obtain the amount
of light that our supposititious planet would receive on its night side
from the nearest stars in the cluster. And since the number of these
stars increases with their distance from the center in the same ratio
as their light diminishes, it follows that the total light received from
the cluster would exceed that received from the dozen nearest stars as
many times as there were spherical shells in the cluster. This would be
about fifteen times, and accordingly all the stars together would shed,
at the center, some thirty times as much light as that of the moon.
Dividing this again by two, because only half of the stars could be seen
at once, we find that the night side of our observer's planet would be
illuminated with fifteen times as much light as the full moon sheds upon
the earth.
It is evident, too, that our observer would enjoy the spectacle of a
starry firmament incomparably more splendid than that which we behold.
Only about three thousand stars are visible to our unassisted eyes at
once on any clear night, and of those only a few are conspicuous, and
two thirds are so faint that they require some attention in order to be
distinguished. But the spectator at the center of the Hercules cluster
would behold some seven thousand stars at once, the faintest of which
would be five times as brilliant as the brightest star in our sky, while
the brighter ones would blaze like nearing suns. One effect of this
flood of starlight would be to shut out from our observer's eyes all the
stars of the outside universe. They would be effaced in the blaze of his
sky, and he would be, in a manner, shut up within his own little
star-system, knowing nothing of the greater universe beyond, in which we
behold his multitude of luminaries, diminished and blended by distance
into a faintly shining speck, floating like a silvery mote in a sunbeam.
If our observer's planet, instead of being situated in the center of the
cluster, circled around one of the stars at the outer edge of it, the
appearance of his sky would be, in some respects, still more wonderful,
the precise phenomena depending upon the position of the planet's orbit
and the station of the observer. Less than half of his sky would be
filled, at any time, by the stars of the cluster, the other half opening
upon outer space and appearing by comparison almost starless--a vast,
cavernous expanse, with a few faint glimmerings out of its gloomy
depths. The plane of the orbit of his planet being supposed to pass
through the center of the spherical system, our observer would, during
his year, behold the night at one season blazing with the splendors of
the clustered suns, and at another emptied of brilliant orbs and faintly
lighted with the soft glow of the Milky-Way and the feeble flickering of
distant stars, scattered over the dark vault. The position of the orbit,
and the inclination of the planet's axis might be such that the glories
of the cluster would not be visible from one of its hemispheres,
necessitating a journey to the other side of the globe to behold
them.[B]
[B] A similar calculation of the internal appearances of the
Hercules cluster, which I made, was published in 1887 in
the "New York Sun."
Of course, it is not to be assumed that the arrangement of the stars in
the cluster actually is exactly that which we have imagined. Still,
whatever the arrangement, so long as the cluster is practically
spherical, and the stars composing it are of nearly uniform size and
situated at nearly uniform distances, the phenomena we have described
would fairly represent the appearances presented to inhabitants of
worlds situated in such a system. As to the possibility of the existence
of such worlds and inhabitants, everybody must draw his own conclusions.
Astronomy, as a science, is silent upon that question. But there shine
the congregated stars, mingling their rays in a message of light, that
comes to us across the gulf, proclaiming their brotherhood with our own
glorious sun. Mathematicians can not unravel the interlocking
intricacies of their orbits, and some would, perhaps _a priori_, have
said that such a system was impossible, but the telescope has revealed
them, and there they are! What purposes they subserve in the economy of
the universe, who shall declare?
If you have a field-glass, by all means try it upon 13 M. It will give
you a more satisfactory view than an opera-glass is capable of doing,
and will magnify the cluster so that there can be no possibility of
mistaking it for a star. Compare this compact cluster, which only a
powerful telescope can partially resolve into its component stars, with
7 M. and 24 M., described before, in order to comprehend the wide
variety in the structure of these aggregations of stars.
The Northern Crown, although a strikingly beautiful constellation to the
naked eye, offers few attractions to the opera-glass. Let us turn, then,
to Lyra. I have never been able to make up my mind which of three great
stars is entitled to precedence--Vega, the leading brilliant of Lyra,
Arcturus in Booetes, or Capella in Auriga. They are the three leaders of
the northern firmament, but which of them should be called the chief, is
very hard to say. At any rate, Vega would probably be generally regarded
as the most beautiful, on account of the delicate bluish tinge in its
light, especially when viewed with a glass. There is no possibility of
mistaking this star because of its surpassing brilliancy. Two faint
stars close to Vega on the east make a beautiful little triangle with
it, and thus form a further means of recognition, if any were needed.
Your opera-glass will show that the floor of heaven is powdered with
stars, fine as the dust of a diamond, all around the neighborhood of
Vega, and the longer you gaze the more of these diminutive twinklers you
will discover.
[Illustration: MAP 11.]
Now direct your glass to the northernmost of the two little stars near
Vega, the one marked Epsilon ([epsilon]) in the map. You will perceive
that it is composed of two stars of almost equal magnitude. If you had a
telescope of considerable power, you would find that each of these stars
is in turn double. In other words, this wonderful star which appears
single to the unassisted eye, is in reality quadruple, and there is
reason to think that the four stars composing it are connected in
pairs, the members of each pair revolving around their common center
while the two pairs in turn circle around a center common to all. With a
field-glass you will be able to see that the other star near Vega, Zeta
([zeta]), is also double, the distance between its components being
three quarters of a minute, while the two stars in [epsilon] are a
little less than 31/2' apart. The star Beta ([beta]) is remarkably
variable in brightness. You may watch these variations, which run
through a regular period of about 12 days, 213/4 hours, for yourself.
Between Beta and Gamma ([gamma]) lies the beautiful Ring nebula, but it
is hopelessly beyond the reach of the optical means we are employing.
Let us turn next to the stars in the west. In consulting the
accompanying map of Virgo and Booetes (Map No. 11), the observer is
supposed to face the southwest, at the hours and dates mentioned above
as those to which the circular map corresponds. He will then see the
bright star Spica in Virgo not far above the horizon, while Arcturus
will be half-way up the sky, and the Northern Crown will be near the
zenith.
The constellation Virgo is an interesting one in mythological story.
Aratus tells us that the Virgin's home was once on earth, where she bore
the name of Justice, and in the golden age all men obeyed her. In the
silver age her visits to men became less frequent, "no longer finding
the spirits of former days"; and, finally, when the brazen age came with
the clangor of war:
"Justice, loathing that race of men,
Winged her flight to heaven; and fixed
Her station in that region
Where still by night is seen
The Virgin goddess near to bright Booetes."
The chief star of Virgo, Spica, is remarkable for its pure white light.
To my eye there is no conspicuous star in the sky equal to it in this
respect, and it gains in beauty when viewed with a glass. With the aid
of the map the reader will find the celebrated binary star Gamma
([gamma]) Virginis, although he will not be able to separate its
components without a telescope. It is a curious fact that the star
Epsilon ([epsilon]) in Virgo has for many ages been known as the
Grape-Gatherer. It has borne this name in Greek, in Latin, in Persian,
and in Arabic, the origin of the appellation undoubtedly being that it
was observed to rise just before the sun in the season of the vintage.
It will be observed that the stars [epsilon], [delta], [gamma], [eta],
and [beta], mark two sides of a quadrilateral figure of which the
opposite corner is indicated by Denebola in the tail of Leo. Within this
quadrilateral lies the marvelous Field of the Nebulae, a region where
with adequate optical power one may find hundreds of these strange
objects thronging together, a very storehouse of the germs of suns and
worlds. Unfortunately, these nebulae are far beyond the reach of an
opera-glass, but it is worth while to know where this curious region is,
even if we can not behold the wonders it contains. The stars Omicron
([omicron]), Pi ([pi]), etc., forming a little group, mark the head of
Virgo.
The autumnal equinox, or the place where the sun crosses the equator of
the heavens on his southerly journey about the 21st of September, is
situated nearly between the stars [eta] and [beta] Virginis, a little
below the line joining them, and somewhat nearer to [eta]. Both [eta]
and [zeta] Virginis are almost exactly upon the equator of the heavens.
The constellation Libra, lying between Virgo and Scorpio, does not
contain much to attract our attention. Its two chief stars, [alpha] and
[beta], may be readily recognized west of and above the head of Scorpio.
The upper one of the two, [beta], has a singular greenish tint, and the
lower one, [alpha], is a very pretty double for an opera-glass.
The constellation of Libra appears to have been of later date than the
other eleven members of the zodiacal circle. Its two chief stars at one
time marked the extended claws of Scorpio, which were afterward cut off
(perhaps the monster proved too horrible even for its inventors) to form
Libra. As its name signifies, Libra represents a balance, and this fact
seems to refer the invention of the constellation back to at least three
hundred years before Christ, when the autumnal equinox occurred at the
moment when the sun was just crossing the western border of the
constellation. The equality of the days and nights at that season
readily suggests the idea of a balance. Milton, in "Paradise Lost,"
suggests another origin for the constellation of the Balance in the
account of Gabriel's discovery of Satan in paradise:
"... Now dreadful deeds
Might have ensued, nor only paradise
In this commotion, but the starry cope
Of heaven, perhaps, or all the elements
At least had gone to wrack, disturbed and torn
With violence of this conflict, had not soon
The Eternal, to prevent such horrid fray,
Hung forth in heaven his golden scales, yet seen
Betwixt Astrea and the Scorpion sign."
Just north of Virgo's head will be seen the glimmering of Berenice's
Hair. This little constellation was included among those described in
the chapter on "The Stars of Spring," but it is worth looking at again
in the early summer, on moonless nights, when the singular arrangement
of the brighter members of the cluster at once strikes the eye.
[Illustration: BERENICE'S HAIR.]
Booetes, whose leading brilliant, Arcturus, occupies the center of our
map, also possesses a curious mythical history. It is called by the
Greeks the Bear-Driver, because it seems continually to chase Ursa
Major, the Great Bear, in his path around the pole. The story is that
Booetes was the son of the nymph Calisto, whom Juno, in one of her
customary fits of jealousy, turned into a bear. Booetes, who had become a
famous hunter, one day roused a bear from her lair, and, not knowing
that it was his mother, was about to kill her, when Jupiter came to the
rescue and snatched them both up into the sky, where they have shone
ever since. Lucan refers to this story when, describing Brutus's visit
to Cato at night, he fixes the time by the position of these
constellations in the heavens:
"'Twas when the solemn dead of night came on,
When bright Calisto, with her shining son,
Now half the circle round the pole had run."
Booetes is not specially interesting for our purposes, except for the
splendor of Arcturus. This star has possessed a peculiar charm for me
ever since boyhood, when, having read a description of it in an old
treatise on Uranography, I felt an eager desire to see it. As my search
for it chanced to begin at a season when Arcturus did not rise till
after a boy's bed-time, I was for a long time disappointed, and I shall
never forget the start of surprise and almost of awe with which I
finally caught sight of it, one spring evening, shooting its flaming
rays through the boughs of an apple-orchard, like a star on fire.
When near the horizon, Arcturus has a remarkably reddish color; but,
after it has attained a high elevation in the sky, it appears rather a
deep yellow than red. There is a scattered cluster of small stars
surrounding Arcturus, forming an admirable spectacle with an opera-glass
on a clear night. To see these stars well, the glass should be slowly
moved about. Many of them are hidden by the glare of Arcturus. The
little group of stars near the end of the handle of the Great Dipper,
or, what is the same thing, the tail of the Great Bear, marks the
upraised hand of Booetes. Between Berenice's Hair and the tail of the
Bear you will see a small constellation called Canes Venatici, the
Hunting-Dogs. On the old star-maps Booetes is represented as holding
these dogs with a leash, while they are straining in chase of the Bear.
You will find some pretty groupings of stars in this constellation.
And now we will turn to the east. Our next map shows Cygnus, a
constellation especially remarkable for the large and striking figure
that it contains, called the Northern Cross, Aquila the Eagle, the
Dolphin, and the little asterisms Sagitta and Vulpecula. In consulting
the map, the observer is supposed to face toward the east. In Aquila
the curious arrangement of two stars on either side of the chief star of
the constellation, called Altair, at once attracts the eye. Within a
circle including the two attendants of Altair you will probably be able
to see with the naked eye only two or three stars in addition to the
three large ones. Now turn your glass upon the same spot, and you will
see eight or ten times as many stars, and with a field-glass still more
can be seen. Watch the star marked Eta ([eta]), and you will find that
its light is variable, being sometimes more than twice as bright as at
other times. Its changes are periodical, and occupy a little over a
week.
The Eagle is fabled to have been the bird that Jupiter kept beside his
throne. A constellation called Antinous, invented by Tycho Brahe, is
represented on some maps as occupying the lower portion of the space
given to Aquila.
The Dolphin is an interesting little constellation, and the ancients
said it represented the very animal on whose back the famous musician
Arion rode through the sea after his escape from the sailors who tried
to murder him. But some modern has dubbed it with the less romantic name
of Job's Coffin, by which it is sometimes called. It presents a very
pretty sight to the opera-glass.
Cygnus, the swan, is a constellation whose mythological history is not
specially interesting, although, as remarked above, it contains one of
the most clearly marked figures to be found among the stars, the famous
Northern Cross. The outlines of this cross are marked with great
distinctness by the stars Alpha ([alpha]), Epsilon ([epsilon]), Gamma
([gamma]), Delta ([delta]), and Beta ([beta]), together with some
fainter stars lying along the main beam of the cross between [beta] and
[gamma]. The star [beta], also called Albireo, is one of the most
beautiful double stars in the heavens. The components are sharply
contrasted in color, the larger star being golden-yellow, while the
smaller one is a deep, rich blue. With a field-glass of 1.6-inch
aperture and magnifying seven times I have sometimes been able to
divide this pair, and to recognize the blue color of the smaller star.
It will be found a severe test for such a glass.
[Illustration: MAP 12.]
About half-way from Albireo to the two stars [zeta] and [epsilon] in
Aquila is a very curious little group, consisting of six or seven stars
in a straight row, with a garland of other stars hanging from the
center. To see it best, take a field-glass, although an opera-glass
shows it.
I have indicated the place of the celebrated star 61 Cygni in the map,
because of the interest attaching to it as the nearest to us, so far as
we know, of all the stars in the northern hemisphere, and with one
exception the nearest star in all the heavens. Yet it is very faint, and
the fact that so inconspicuous a star should be nearer than such
brilliants as Vega and Arcturus shows how wide is the range of magnitude
among the suns that light the universe. The actual distance of 61 Cygni
is something like 650,000 times as great as the distance from the earth
to the sun.
The star Omicron ([omicron]) is very interesting with an opera-glass.
The naked eye sees a little star near it. The glass throws them wide
apart, and divides [omicron] itself into two stars. Now, a field-glass,
if of sufficient power, will divide the larger of these stars again into
two--a fine test.
Sweep around [alpha] and [gamma] for the splendid star-fields that
abound in this neighborhood; also around the upper part of the figure of
the cross. We are here in one of the richest parts of the Milky-Way.
Between the stars [alpha], [gamma], [epsilon], is the strange dark gap
in the galaxy called the Coal-Sack, a sort of hole in the starry
heavens. Although it is not entirely empty of stars, its blackness is
striking in contrast with the brilliancy of the Milky-Way in this
neighborhood. The divergent streams of the great river of light in this
region present a very remarkable appearance.
[Illustration: MAP 13.]
Finally, we come to the great dragon of the sky. In using the map of
Draco and the neighboring constellations, the reader is supposed to face
the north. The center of the upper edge of the map is directly over the
observer's head. One of the stories told of this large constellation is
that it represents a dragon that had the temerity to war against
Minerva. The goddess "seized it in her hand, and hurled it, twisted as
it was, into the heavens round the axis of the world, before it had time
to unwind its contortions." Others say it is the dragon that guarded the
golden apples in the Garden of the Hesperides, and that was slain by the
redoubtable Hercules. At any rate, it is plainly a monster of the first
magnitude. The stars [beta], [gamma], [xi], [nu], and [mu] represent its
head, while its body runs trailing along, first sweeping in a long
curve toward Cepheus, and then bending around and passing between the
two bears. Try [nu] with your opera-glass, and if you succeed in seeing
it double you may congratulate yourself on your keen sight. The distance
between the stars is about 1'. Notice the contrasted colors of [gamma]
and [beta], the former being a rich orange and the latter white. As you
sweep along the winding way that Draco follows, you will run across many
striking fields of stars, although the heavens are not as rich here as
in the splendid regions that we have just left. You will also find that
Cepheus, although not an attractive constellation to the naked eye, is
worth some attention with an opera-glass. The head and upper part of the
body of Cepheus are plunged in the stream of the Milky Way, while his
feet are directed toward the pole of the heavens, upon which he is
pictured as standing. Cepheus, however, sinks into insignificance in
comparison with its neighbor Cassiopeia, but that constellation belongs
rather to the autumn sky, and we shall pass it by here.