THE STARRY HEAVENS
TRIPLE, QUADRUPLE, AND MULTIPLE STARS.--These, when observed with the
naked eye, appear as single stars, but, when examined with a high
magnifying power, each lucid point can be resolved into several
component stars. They vary in number from three to half a dozen or more,
and form systems of a more complex character than what are observed in
the case of binary stars. In the usual construction of a triple system,
the secondary star of a binary is resolvable into two, each star being
in mutual revolution, whilst they both gravitate round their primary. By
another arrangement, a close pair control the movements of a distant
attendant.
One of the most interesting of triple stars is the tricoloured Gamma
Andromedae. The brilliant components of this system have their
counterparts in the topaz, the emerald, and the sapphire--the larger
star is of the third magnitude and of a golden yellow colour; the
secondary of the fifth magnitude and of an emerald green. These stars
are ten seconds apart, and, though they have been under observation
since 1777, no orbital movement has as yet been detected, but their
common proper motion indicates their close relationship and physical
connection. In 1842, Otto Struve discovered that the companion star is
itself double, and round it there gravitates a sapphire sun, which is
believed to accomplish a revolution of its orbit in about 500 years. If
round those suns there should be circling planetary systems of worlds
inhabited by intelligent beings, the varied effects produced by the
light emanating from those different coloured orbs would be of a very
beautiful and pleasing nature.
A system suggestive of the endless variety of stellar arrangement that
exists throughout the sidereal regions is apparent in the case of the
triple star Zeta Cancri. Two of the stars, of magnitudes six and seven,
form a binary in rapid revolution, the components of which complete a
circuit of their orbits in fifty-eight years, whilst the more distant
third star, of almost similar magnitude, accomplishes a wide orbital
ellipse round the other two in 500 or 600 years. These stars have been
closely observed by astronomers during the past forty years, with the
result that their motions have appeared most perplexing, and complicated
beyond precedent. 'If this be really a ternary system,' wrote Sir John
Herschel, 'connected by the mutual attraction of its parts, its
perturbations will present one of the most intricate problems in
physical astronomy.' The second star revolves round its primary, whilst
the third pursues a retrograde course, but its path, instead of being
even, presents the appearance of a series of circular loopings, in
traversing which the star alternately quickens and slackens its pace,
or at times appears to be stationary.
Astronomers have arrived at the conclusion that these perturbations are
produced by the presence of a fourth member, which, though invisible, is
probably the most massive of the system--perhaps a magnificent world
teeming with animated beings, and attended by three suns which gravitate
round it, dispensing light and heat to meet the requirements of the
various forms of life which exist on its surface. In this system we have
an arrangement the reverse of what exists in the solar system, where all
the planets revolve round a predominant sun; but here there is a strange
verification of the old Ptolemaic belief with regard to the path of a
sun, though in this instance there are three suns circling round a dark
globe which they illumine and vivify.
Triple stars occur with comparative frequency throughout the heavens. In
Monoceros there is a fine triple star, discovered by Herschel, which he
describes as 'one of the most beautiful sights in the heavens.' The
stars Xi and Beta Scorpii form triple systems in which the components
are differently arranged. In Xi the primary and secondary consist of two
revolving stars which control the movements of a distant attendant; in
Beta the primary and secondary stars are in mutual revolution, whilst
round the former there circles a very close minute companion. There are
doubtless many binary stars which, if examined with adequate telescopic
power, would resolve themselves into triple and multiple systems, but
the profound distances of those objects render the detection of their
components a most difficult task.
Quadruple stars are usually arranged in pairs, _i.e._ the primary and
secondary of a binary system are each resolvable into two, forming two
pairs, each pair being in mutual revolution, while they both gravitate
round their common centre of gravity. Epsilon Lyrae, which has been
described as a double double, is an example of a quadruple system, and
Nu Scorpii is of a similar construction, but more beautiful because its
components are in closer proximity to each other. Close upon twenty of
those double double systems have been discovered in different parts of
the heavens.
One of the most interesting of quadruple systems is Theta Orionis, which
is situated in the Great Nebula, by which it is surrounded. This star,
when observed with a telescope of low power, can be at once resolved
into four separate lucent points, so arranged as to form a quadrilateral
figure or trapezium. They are of the fifth, sixth, seventh, and eighth
magnitudes, and described as pale white, garnet, faint lilac, and red.
Though they have been under careful observation for upwards of two
centuries, no perceptible motion has been perceived as occurring among
them, nor has there been any change in their relative positions--they
appear to be perfectly motionless; but we must not infer from this that
no physical bond of union exists between them, for they are situated at
an amazing distance from the Earth. Ascending higher in the scale of
celestial architecture, we have multiple stars forming systems still
more elaborate and complex, into the structure of which numerous stars
enter, and they, as they increase in number, gradually merge into
star-clusters.
If we assume that around each of the components of a multiple star there
circles a retinue of planetary worlds, we are confronted with a most
perplexing problem as to how the dynamical stability of a system so
different from, and so vastly more complicated than, that of our solar
system is maintained--where, as it were, suns and planets
intermingle--how numerous circling orbs can accomplish their revolutions
without being swayed and deflected from their paths by the gravitational
attraction of adjacent members of the same system. Perplexing though the
arrangement of such a scheme may be to our conception, yet, each orb has
been weighed, poised, and adjusted by Infinite Wisdom, to perform its
intricate motions in synchronous harmony with other members of the
system--all moving in unison like the parts of a complicated piece of
mechanism, and maintained in stable equilibrium by their mutual
attraction--
Mystical dance, which yonder starry sphere
Of planets and of fixed in all her wheels
Resembles nearest; mazes intricate,
Eccentric, intervolved, yet regular
Then most, when most irregular they seem;
And in their motions harmony divine
So smooths her charming tones that God's own ear
Listens delighted.--v. 620-27.
All the natural phenomena with which we are familiar would, in the case
of planets revolving round the component suns of a multiple system, be
of a different kind or altogether absent. Instead of being illumined by
one sun, those worlds would, at certain times, have several suns--some
more distant than others--above their horizons, and upon very rare
occasions, if ever, would there be an entire absence of all of those
orbs from their skies. Consequently there would be no year such as we
are familiar with; no regular sequence of seasons similar to what is
experienced on Earth; no alternation of day and night, for there would
be '_no night there_,' though, in the absence of the primary orb, the
light emitted by distant suns, whilst sufficient to banish night, and
beyond comparison brighter than the Moon when at full, would, in the
diminution of its intensity from that of noonday, be as grateful a
change as that of from day to night which occurs on our globe.
Should those suns be differently coloured, each emitting its own
peculiar shade of light as it appears above the horizon, the varied
aspects of the perpetual day enjoyed by the inhabitants of those
circling worlds present to the imagination harmonies of light and shade
over which it is pleasant to linger.
TEMPORARY, PERIODICAL, AND VARIABLE STARS.--It may seem remarkable that
among so many thousands of stars which spangle the firmament, there
should occur no very perceptible change or variation in their aspect
and brilliancy. From age to age they present the same appearance, shine
with the same undiminished splendour, and rise and set with the same
regularity. So that from time immemorial the stars have been regarded by
mankind as the embodiment of all that is eternal and unchangeable. Yet,
the serenity of the celestial regions does not always remain
undisturbed--at occasional times a 'Nova,' or new star, blazes forth
unexpectedly in the heavens, and perplexes astronomers; and, after
shining with a varying degree of brilliancy for a few weeks or months,
gradually diminishes in size and brightness and eventually becomes lost
to sight.
A record has been kept of about twenty temporary stars that have been
observed at various periods since the time that reliable data of those
objects have been published. Pliny mentions the appearance of a new star
in the time of Hipparchus (134 B.C.); it was seen in the constellation
of the Scorpion, and it is said that it was the apparition of this star
which induced the celebrated astronomer to construct what is known as
the earliest star catalogue. A new star is said to have become visible
when the Emperor Honorius ruled, and another during the reign of the
Emperor Otho, about 945 A.D. In May 1012 a new star appeared in Aries,
and in July 1203 another was observed in Scorpio, which resembled
Saturn. The most remarkable star of this kind was one observed by Tycho
Brahe, which appeared in the constellation Cassiopeia. He first
perceived it on November 11, 1572. In lustre it equalled Jupiter, and
when at its brightest rivalled Venus; it was visible at noonday, and at
night its light could be perceived through strata of cloud which
rendered all other stars invisible. The star maintained its brilliancy
for three weeks, when it became of a yellowish colour and perceptibly
decreased in size; it afterwards assumed a ruddy hue resembling
Aldebaran, and, diminishing gradually in magnitude and brightness,
ceased to be visible in March 1574. It twinkled more than the other
stars, and during the time it could be perceived its position remained
unchanged. In 1604 a conspicuous new star burst forth in Ophiuchus. It
surpassed in brilliancy stars of the first magnitude, and outshone the
planet Jupiter, which was in its proximity. Kepler observed this star,
and described it as 'sparkling like a diamond with prismatic tints.' It
soon began to decline after its appearance; in March 1605 it had shrunk
to the dimensions of a third-magnitude star, and in a year later it
became entirely lost to view. Other stars of the same class, though of a
less conspicuous character, have been observed at occasional times.
Anthelme, a Carthusian monk, discovered one near Beta Cygni in 1670;
another appeared in Ophiuchus in 1848; one in Scorpio in 1860; one in
Corona Borealis in 1866; in Cygnus in 1876; in Andromeda in 1885; and in
Auriga in 1892.
Various theories have been advanced in order to account for the sudden
outbursts of those stars, the light from which has probably occupied
not much less than one hundred years in its passage hither. It has been
suggested that the collision of two suns, or of two great masses of
matter, would create such phenomena; but, apart from the improbability
of such a catastrophe occurring among the celestial orbs, the rapid
subsidence in the luminosity of the observed objects would indicate that
the outburst was produced by causes of a more rapidly transitory nature
than what would result from the collision of two condensed masses of
matter. A collision occurring between two swarms of meteors has been
suggested as one way of accounting for the sudden appearance of those
stars; but another, and more plausible, explanation is that they are
produced by a great eruption of glowing gas from the interior of a sun,
causing an enormous increase in its luminosity, which subsides after a
time, and is succeeded by a normal condition of things. It has been
observed that all those temporary stars, with the exception of two, have
appeared in the region of the Milky Way. In this luminous zone the
condensation of small gaseous stars and nebulae is more pronounced than
in any other part of the heavens, and this would seem to indicate that
there may be cosmical changes taking place among them which need not be
associated with the occurrence of catastrophes resulting in the
conflagration of worlds, and that Nature, in accomplishing her purposes,
does not overstep the uniform working of her laws, upon which depend the
stability and existence of the universe.
PERIODICAL AND VARIABLE STARS are distinguished from other similar
objects by the fluctuations which occur in the quantity of light emitted
by them. The difference in the luminosity of some stars is at times so
marked that, in a few weeks or months, they decline from the first or
second magnitudes to invisibility, and, after the expiration of a
certain period, they again gradually regain their pristine condition.
When these changes take place with regular recurrence, they are called
'periodical;' when they occur in a variable and uncertain manner, they
are called 'irregular.' About 300 stars are known as variable, but the
majority of them are telescopic objects. Their periodical changes of
brilliancy present every degree of variety; in some stars they are
scarcely perceptible and occur at long intervals; in others, changes of
brightness occur in a few hours or days, by which the light emitted is
intensified many hundreds of times.
Some stars accomplish their cycle of change in a few days, many in a few
weeks or months, and there are others which do not complete their
periods until the expiration of a number of years.
One of the most remarkable of variable stars is called Mira 'the
wonderful,' in the constellation Cetus. When at its maximum brilliancy
it shines for two or three weeks as a star of the second magnitude. It
then begins to gradually decline, and at the end of three months becomes
invisible. It remains invisible for five months, and then reappears, and
during the ensuing three months it regains by degrees its former
brilliancy. Mira completes a cycle of its changes in 334 days, and,
during that time, oscillates between a star of the second and tenth
magnitude. The variability of Mira Ceti was first observed by David
Fabricius in the sixteenth century.
Another remarkable star is Eta Argus, which is surrounded by the great
nebula in the constellation Argo Navis. It is invisible to the naked
eye, but in the telescope it has a reddish appearance, and is slightly
brighter than the stars in its vicinity. It was first observed by Halley
in 1677, and it was then of the fourth magnitude. In 1751 it had risen
to the second magnitude, and maintained its position as a star of this
class until 1837, when, on December 16 of that year, its brilliancy
suddenly increased, and it equalled in a short time Alpha Centauri. It
reached its maximum in 1843, and then it was surpassed only by Sirius.
It maintained its brilliancy for about ten years. In 1858, it declined
to the second magnitude, in 1859 to the third, and, gradually
diminishing, it became invisible to the naked eye in 1868. It is now of
the seventh magnitude, and is again increasing, and may soon resume its
position among the other stars. It is believed to have a period of
seventy years, and in that time its light ebbs and flows between the
seventh and first magnitudes.
The most interesting variable star in the heavens is Algol (the demon),
in the constellation Perseus. Its light fluctuations can be observed
without the aid of a telescope, and it completes a cycle of its changes
in two or three days. For about two days and thirteen hours it is
conspicuously visible as a star of the second magnitude; it then begins
to decline, and in about four hours sinks to the dimensions of a
fourth-magnitude star; it remains in this condition for twenty minutes,
and then increases gradually until, at the expiration of four hours, it
regains its former brilliancy, which it sustains for two days and
thirteen hours, when it again goes through the same cycle of changes in
a precisely similar manner to what has been described. Astrologers have
ascribed many evil influences to the demon star, which adorned the head
of Medusa; nor did it escape the observation of ancient astronomers that
this malevolent orb is--as a modern writer amusingly remarks--slowly
winking at us from out the depths of space.
Variable stars are found in greater numbers in some parts of the heavens
than in others. Those of a white colour, and with shorter and more
regular periods, are most numerous in the region of the Milky Way; those
that are small, with long periods and of a reddish hue, are more widely
removed from that zone. Stars of this class are all very remote, and no
attempt has as yet been made to ascertain the parallax of Algol.
Several theories have been suggested in order to account for the
periodical brilliancy of those stars. It has been suggested that the
stars have opaque non-luminous patches on their surfaces, and that
during axial rotation their light ebbs and flows according as the dark
or bright portions are turned towards us. This theory is highly
improbable. Another and more plausible reason, especially with regard to
short period variables, is, that around those stars there revolve opaque
bodies or satellites which at times intercept a portion of their light
by producing a partial eclipse of their discs, similar to that caused by
the dark body of the Moon when passing between the Sun and the Earth.
It is now known that in the case of variables of the Algol type, the
periodical fluctuations of their light arises from this cause, and that
round Algol there is a dark world or satellite travelling, which
completes a revolution of its orbit in about sixty-nine hours, and that,
during each circuit, it intercepts one half of the light of its primary
by partially eclipsing the orb, and thereby creating a diminution in its
apparent magnitude which becomes perceptible at recurring intervals.
STAR GROUPS.--These are plentifully scattered over the heavens and, by
their conspicuous brilliancy, add to the grandeur and magnificence of
the midnight sky. The Hyades in Taurus, of which Aldebaran is the chief,
forming the eye of the Bull, attract attention.
The stars in Coma Bernices form a rich group; the sickle in Leo, the
seven stars in Ursa Major, and those in Cassiopeia and Aquila are
familiarly known to all observers. Besides these, there are many other
groups and aggregations of stars which adorn the celestial vault and
enhance the beauty of the heavens.
STAR CLUSTERS.--On observing the heavens on a clear, dark night, there
can be seen in different parts of the sky closely aggregated groups of
stars called clusters. In some instances the component stars are so near
together that the naked eye is unable to discern the individual members
of the cluster. They then assume an indistinct, hazy, cloudlike
appearance. Upwards of 500 clusters are known to astronomers, the
majority of which are very remote. Many of them contain thousands of
stars compressed into a very small space, and others are so distant that
the largest telescopes are incapable of resolving their nebulous
appearance into separate stars.
Star clusters have been arranged into two classes, 'irregular' and
'globular;' but no sharp line of demarcation exists between them, though
each have their distinctive peculiarities. Irregular clusters consist of
aggregations of stars brought promiscuously together, and presenting an
appearance devoid of any structural arrangement. They are of different
shapes and sizes, possess no distinct outline, and are not condensed
towards their centre, like those that are globular. On examination, they
present an intricate reticulated appearance; streams and branches of
stars extend outwards from the parent cluster, sometimes in rows and
sinuous lines, and, in other instances, diverging from a common centre,
forming sprays. Sometimes the stars are seen to follow each other on the
same curve which terminates in loops and arches of symmetrical
proportions.
There are three conspicuous clusters in the northern sky that are
visible to the naked eye--viz. the Pleiades in Taurus, the Great Cluster
in the sword-handle of Perseus, and Praesepe in Cancer, commonly called
the Beehive.
The cluster which from time immemorial has had bestowed upon it the
chief attention of mankind are the beautiful Pleiades or Seven Sisters,
and intertwined among its stars are the legendary and mythological
beliefs of ancient nations and untutored tribes inhabiting the different
regions of the globe. When viewed with a telescope of moderate size the
cluster appears as a scattered group, and numerous stars become visible
that are imperceptible to ordinary vision.
In the sword-handle of Perseus there is a cluster which, to the naked
eye, appears as a small patch of luminous cloud. This inconspicuous
object when observed with an instrument of moderate power is resolved
into a magnificent assemblage of stars, and presents a spectacle which
creates in the mind of the beholder mingled feelings of admiration and
amazement. No telescope has yet penetrated its utmost depths, or
revealed all the glories of this shining region, crowded with glittering
points of light comparable in number to the pebbles strewn on the shore
of a troubled sea.
The cluster Praesepe in Cancer is visible on a clear night to the
unaided eye as a small nebula. This object attracted the attention of
Galileo, to which he applied his newly invented telescope, and was
delighted to find that his glass was capable of resolving it into a
group of stars thirty-six in number, and all of comparatively large
magnitude. The disappearance of Praesepe in consequence of the
condensation of vapour in the atmosphere was regarded by the ancients as
a sure indication of approaching rain. In the same constellation, near
the Crab's southern claw, there is another rich cluster, which consists
of 200 stars of the ninth and tenth magnitudes.
In Sobieski's Shield there is a magnificent fan-shaped cluster of minute
stars with a prominent one in its centre; and in the constellation of
the Southern Cross there is a cluster which, on account of the varied
colours of its component stars, has been compared by Sir John Herschel
to 'a piece of rich fancy jewellery;' eight of the principal stars being
coloured red, green, and blue.
GLOBULAR CLUSTERS.--These have been described by Herschel as 'the most
magnificent objects that can be seen in the heavens.' They are all very
remote, of a rounded form, and when viewed with a telescope present the
appearance of 'a ball of stars.' In some clusters the constituent stars
are distinguishable as minute points of light; in others, more remote,
they are of a coarse granular texture, and in those still more distant
they resemble a 'heap of golden sand.' Some clusters are situated at
such a profound distance in space that it is impossible with the most
powerful of telescopes to define their stellar structure; all that can
be distinguished of these is a cloudy luminosity resembling in
appearance an irresolvable nebula. Globular clusters usually present a
radiated appearance. Rays, branches, and spiral-shaped streams of stars
appear to flow from the circumference of some; and, in other instances,
fantastic appendages of stars project outwards from the parent cluster.
There doubtless exists much variety in the structural arrangement of
these clusters, and an equal diversity in the magnitude and number of
the stars which enter into their formation. The stars in some clusters
may equal those of the first magnitude, and in others they may not
exceed in dimensions the minor planets. In the telescope they vary in
size from the eleventh to the fifteenth magnitude; the smaller stars
occupy the centre of a cluster, whilst the larger ones are found near
its circumference. Globular clusters are more condensed towards their
centre than those of irregular shape, and some have a nucleated
appearance. This apparent condensation is not altogether owing to the
depth of star strata as viewed from the circumference of the cluster,
but there appears to exist an attractive force (probably gravitational)
which draws the stars towards its centre, and if this 'clustering power'
were not opposed by some other counteracting force, those bodies would
coalesce into one mass. It may be 'that a centrifugal impulse
predominates by which full-grown orbs are driven from the nursery of
suns in which they were reared to seek their separate fortunes and enter
on an independent career elsewhere.'
It is not known how the dynamical equilibrium of a star cluster is
maintained; and on account of its extreme distance no motion is
perceptible among its component stars. The laws by which those stellar
aggregations are produced and governed are wrapped in obscurity, and the
nature of the motions of their stars, whether towards concentration or
diffusion, cannot at present be ascertained. If those globular clusters
could be observed sufficiently near, they would most probably expand
into vast systems of suns occupying immense regions of space.
The largest and most magnificent globular cluster in the heavens is
Omega Centauri, in the Southern Hemisphere. To the naked eye it
resembles a round, indistinct, cometary object, about equal to a star of
the fourth magnitude; but when observed with a powerful telescope it
appears as a globe of considerable dimensions composed of innumerable
stars of the thirteenth and fifteenth magnitudes, all exceedingly minute
and gathered into small knots and groups. A remarkable cluster in
Toucani is described by Sir John Herschel as 'most magnificent; very
large; very bright, and very much compressed in the middle.' The
interior mass consists of closely aggregated pale rose-coloured stars,
surrounded by others of a pure white which embrace the remainder of the
cluster. There is a fine globular cluster in Sagittarius between the
Archer's head and the bow. It was observed by Hevelius in 1665. The
central portion is very much compressed, and consists of excessively
minute stars enclosed by others of larger size. In Aquarius there is a
magnificent ball of stars of a beautiful spherical form, which Sir J.
Herschel compared to a heap of fine sand. Numerous other clusters are
profusely distributed over the heavens, occupying regions in the
profound depths of space which can only be reached by the aid of most
powerful instruments.
The finest and most remarkable object of this class visible in the
northern heavens is the Great Cluster which lies between Eta and Zeta
Herculis. It was discovered by Halley in 1714, who writes: 'This is but
a little patch, but it shows itself to the naked eye when the sky is
serene and the moon absent.' When observed with a powerful telescope its
magnificence at once becomes apparent to the beholder. 'Perhaps,' says
Dr. Nichol, 'no one ever saw it for the first time through a telescope
without uttering a shout of wonder.' At its circumference the stars are
rather scattered, but towards the centre they appear so closely
aggregated that their combined effulgence forms a perfect blaze of
light. Sir William Herschel estimated that there are 14,000 stars in the
cluster, each a magnificent world but unaccompanied by any planetary
attendants.
[Illustration: CLUSTER IN HERCULES]
As a result of more recent investigations this number has been
considerably reduced, and it is now generally believed that about 4,000
stars enter into the formation of the cluster. As its distance from the
Earth is unknown, it follows that there must be some uncertainty
attached to any conclusions that may be arrived at with regard to this
superb object. Miss Agnes Clerke estimates the number of the constituent
stars at 4,000, and in support of her conclusion this talented lady
writes as follows: 'The apparent diameter of this object, including most
of the "scattered stars in streaky masses and lines" which form a sort
of "glory" round it, is 8'; that of its truly spherical portion may be
put at 5'. Now, a globe subtending an angle of 5' must have (because the
sine of that angle is to radius nearly as to 1 : 687) a real diameter
1/687 of its distance from the eye, which, if we assume to be such as
would correspond to a parallax of 1/20 of a second, we find that the
cluster, outliers apart, measures 558,000 millions of miles across.
Light, in other words, occupies thirty-six days in traversing it, but
sixty-five years in journeying thence hither. Its components may be
regarded, on an average, as of the twelfth magnitude; for, although the
divergent stars rank much higher in the scale of brightness, the central
ones, there is reason to believe, are notably fainter. The sum total of
their light, if concentrated into one stellar point, would at any rate
very little (if at all) exceed that of a third-magnitude star. And one
star of the third is equivalent to just four thousand stars of the
twelfth magnitude. Hence we arrive at the conclusion that the stars in
the Hercules Cluster number much more nearly four than fourteen
thousand.'
For what purpose do those thousands of clustering orbs shine? Who can
tell? Night is unknown in the regions illumined by their brilliant
radiance. This stupendous aggregation of suns testifies to the
magnificence of the starry heavens, and to the omnipotence of the
Creator.
GALAXIES.--These consist of vast aggregations of stars which form
separate 'island universes' floating in the depths of space; they are
believed to equal in magnitude and magnificence the Milky Way--the
galaxy to which our system belongs.
NEBULAE.--We now reach the last, and what are believed to be the most
distant of the known contents of the heavens. They are all exceedingly
remote, devoid of any perceptible motion, faintly luminous, and, with
the exception of two of their number, invisible to the naked eye. Halley
was the first astronomer who paid any attention to those objects. In
1716 he enumerated six of them, but of this number only two can, in a
strict sense, be regarded as nebulae, the others since then have been
resolved into magnificent star clusters. In 1784, Messier catalogued 103
nebulae, and the Herschels--father and son--in their survey of the
stellar regions, discovered 4,000 of those objects. There are now 8,000
known nebulae in the heavens, but the majority of them are not of much
interest to astronomers. Prior to the invention of the spectroscope it
was believed that all nebulae were irresolvable star clusters, but the
analysis of their light by this instrument indicated that their
composition was not stellar but gaseous. Their spectra consist of a few
bright lines revealing the presence of hydrogen, nitrogen, and other
gaseous elements.
Much that is mysterious and uncertain is associated with those objects
which appear to lie far beyond the limits of our sidereal system. It is
now generally believed that they exhibit the earliest stage in the
formation of stars and planets--inchoate worlds in process of slow
evolution, which will eventually condense into systems of suns, and
planetary worlds.
Nebulae present every variety of form. Some are annular, elliptic,
circular, and spiral; others are fan-shaped, cylindrical, and irregular,
with tufted appendages, rays, and filaments. A fancied resemblance to
different animated creatures has been observed in some. In Taurus there
is a nebula called the 'Crab' on account of its likeness to the
crustacean; another is called the 'Owl Nebula' from its resemblance to
the face of that bird. The Orion Nebula suggests the opened jaws of a
fish or sea monster, hence called the Fish-Mouth Nebula. There is a
Horse-Shoe Nebula, a Dumb-Bell Nebula, and many others of various shapes
and forms. They are classified as follows: (1) Annular Nebulae, (2)
Elliptic Nebulae, (3) Spiral Nebulae, (4) Planetary Nebulae, (5) Nebulous
Stars, (6) Large Irregular Nebulae.
ANNULAR NEBULAE.--These resemble in appearance an oval-shaped luminous
ring; they are comparatively few in number, and not more than a dozen
have been discovered in the whole heavens. The most remarkable object of
this class is the Ring Nebula, which is situated between the stars Beta
and Gamma Lyrae. It is visible in a moderate-sized telescope as a
well-defined, flat, oval ring; its central part is not quite dark but is
occupied by a filmy haze of luminous matter which is prolonged inwards
from the margin of the ring. When examined with a high power the edges
of the ring have a fringed appearance, and numerous glittering stellar
points become visible both within and without its circumference. This
nebulous ring, though a small object in the telescope, is of enormous
magnitude, and if it were not more distant than 61 Cygni, one of the
nearest of the fixed stars, its diameter would not be less than 20,000
millions of miles, but it has been estimated by Herschel that it is 900
times more remote than Sirius. How stupendous, then, must be its
dimensions, and how bewildering to our conception is the profound
immensity of space in which it is located! An annular nebula similar to
that of Lyra, but on a smaller scale, is found in Cygnus, and within it
there can be seen a conspicuous star. Another exists in Scorpio which
contains two stars situated within the ring at diametrically opposite
points to each other.
ELLIPTICAL NEBULAE.--The most interesting object of this class is the
Great Nebula in Andromeda, called 'the transcendentally beautiful queen
of the nebulae'--an appellation which it scarcely merits. This object,
which is plainly visible to the naked eye, is of an oval shape, of a
milky white colour, and is situated near the most northern star of the
three which form the girdle of Andromeda. It was known to the ancients,
and Ali Sufi, a Persian astronomer who flourished in the tenth century,
alludes to it; but it did not attract much attention until the
seventeenth century. Simon Marius was the first to observe this object
with a telescope. This he did on December 15, 1612; he describes it as
shining with a pale white light resembling in appearance the flame of a
candle when seen through a semi-transparent piece of horn. When examined
with a high magnifying power it is seen to occupy a largely extended
area measuring 4 deg. in length and 2-1/2 deg. in breadth. Its luminosity
increases from the circumference to the centre, where there can be seen
a small nucleus with an ill-defined boundary, which has the appearance
of being granular, but its composition is not stellar. Two dark channels
running almost parallel to each other and to the axis of the nebula have
been observed by Bond; these, when prolonged, form into curves which
terminate in two great rings. They are wide rifts which separate streams
of nebulous matter, and are indicative that some formative processes may
be going on within the nebula.
Astronomers have been baffled in their attempts to discover the nature
of the Andromeda Nebula. Though great telescopes have been able to
render visible thousands of stars over and around it, yet the nebula
itself is irresolvable and bears no trace of stellar formation;
neither, according to Dr. Huggins, is its spectrum gaseous, a
circumstance which deepens the mystery associated with this object. Its
distance is unknown, and its dimensions cannot be ascertained.
Other elliptical nebulae are found in different regions of the heavens.
In Ursa Major there is an oval nebula resembling that of Andromeda, but
on a much smaller scale. It possesses a nucleus, and on the photographic
plate there can be detected the presence of spiral structure, indicating
the existence of streams of nebulous matter. Adjacent to this nebula is
another of the same class with a double nucleus, and associated with it
is a nebulous star.
SPIRAL NEBULAE.--The great reflector of Earl Rosse at Parsonstown was the
successful means by which nebulae of this form were discovered. This
powerful telescope was capable of defining with greater accuracy the
structural formation of those objects than any other instrument in use.
It was ascertained that spiral coils and convoluted whorls enter into
the structure of most nebulae, indicating a similarity in the process of
change which may be going on in these vast accumulations of cosmical
matter. The most interesting specimen of a spiral nebula is situated in
Canes Venatici. It consists of spiral coils emanating from a centre with
a nucleus and surrounded by a narrow luminous ring. In appearance it
resembles the coiled mainspring of a watch.
PLANETARY NEBULAE.--These have been so named on account of the
resemblance which they bear to the discs of planets. They are of uniform
brightness, circular in shape, with sharply-defined edges, and are
frequently of a bluish colour. They are more numerous than annular
nebulae; three-fourths of their number are in the Southern Hemisphere,
and they are situated in or very near the Milky Way. Those objects were
first described by Sir William Herschel, who was rather perplexed as to
what was their real nature and how he should classify them. He remarked
that they could not be planets belonging to far-off suns, nor distant
comets, nor distended stars. Consequently, he concluded rightly that
they were nebulae. When observed with large telescopes, they lose their
planetary aspect, and their sharpness of outline is less apparent; their
discs become broken up into bright and dark portions, and in some,
numerous minute stars have been observed, whilst others have
well-defined nuclei.
The most prominent nebula of this class is situated in the constellation
Ursa Major, and is called the Owl Nebula, from its fancied resemblance
to the face of that bird. Sir John Herschel describes it as 'a most
extraordinary object, a large, uniform nebulous disc, quite round, very
bright, not sharply defined, but yet very suddenly fading away to
darkness.' When examined in 1848 with Earl Rosse's reflector, two bright
stars were discovered in its interior; each was in the centre of a
circular dark space surrounded by whorls of nebulous matter--hence the
origin of its name. This nebula gives a bright line spectrum indicative
of gaseous composition. It is believed to consist chiefly of hydrogen
and other gases which form a globe of such stupendous magnitude that, if
we surmise its distance from the earth to be sixty-five light years--an
estimate much too low--'its diameter would exceed that of the orbit of
Neptune upwards of 100 times.'[10] Within its compass the orbs of
hundreds of solar systems as large as that of ours would be able to
perform their revolutions, having spacious intervals existing between
each system. Another interesting planetary nebula is in the
constellation of the Dragon, near to the pole of the ecliptic; it is
slightly oval, of a pale blue colour, and contains a star of the
eleventh magnitude in its centre. It gives a gaseous spectrum. Attempts
have been made to determine its parallax, but without success, and
during the eighty years it has been under observation it has remained
apparently motionless. Its light period, if estimated at 140 years,
would indicate the existence of a globe with a diameter equal to
forty-four diameters of the orbit of the planet Neptune.[11] A nebula of
this class was discovered by Sir John Herschel in the Centaur. He
described it as resembling Uranus, but larger; its colour was of a
beautiful rich blue, and its light equalled that of a star of the
seventh magnitude.
NEBULOUS STARS.--These stars are each surrounded by a luminous haze
several minutes of arc in diameter and of a circular form. Sir William
Herschel, by his observation of those objects, arrived at the conclusion
'that there exists in space a shining fluid of a nature totally unknown
to us, and that the nebulosity about those stars was not of a starry
nature.' Thirteen stars of this type have been enumerated by him and
many others have since been discovered. The 'glow' which surrounds them
has been observed in a few instances to have vanished without leaving
any trace of nebulosity behind, but the causes which have brought about
such a result are entirely unknown. The nature of those stars is
involved in considerable obscurity, and one class of nebula would seem
to merge into the other; nebulous stars with faint aureolae do not differ
much from small nebulae interspersed with stellar points.
LARGE IRREGULAR NEBULAE.--These are found in both hemispheres, and are
remarkable on account of the varied appearances which they present, and
the large extent of space which many of them occupy. In some, the
nebulous matter of which they are composed can be seen like masses of
tufted flocculi, sometimes piled up, and at other times promiscuously
scattered, resembling in appearance the foam on the crested billows of a
surging ocean rendered suddenly motionless, or cirro-cumuli floating in
a tranquil sky. Islands of light with intervening dark channels,
promontories projecting into gulfs of deep shade, sprays of luminous
matter, convoluted filaments, whorls, wreaths, and spiral streams all
enter into the structural formation of a great nebula.
The Great Nebula in Argo, in the Southern Hemisphere, is one of the most
remarkable objects of this class. It consists of bright irregular masses
of luminous matter, streaks and branches, and occupies an area about
equal to one square degree. At its eastern border is situated the
variable star Eta Argus, which fluctuates between the first and seventh
magnitudes in a period of about seventy years.
A rich portion of the Galaxy lies in front of the nebula, which creates
an effect as if it were studded over with stars. Sir John Herschel, in
describing this nebula, writes as follows:--'The whole is situated in a
very rich and brilliant part of the Milky Way, so thickly strewed with
stars that, in the area occupied by the nebula, not less than 1,200 have
been actually counted. Yet it is obvious that these have no connection
whatever with the nebula, being, in fact, only a simple continuation
over it of the general ground of the Galaxy. The conclusion can hardly
be avoided that, in looking at it, we see through and beyond the Milky
Way, far out into space, through a starless region, disconnecting it
altogether from our system. It is not easy for language to convey a full
impression of the beauty and sublimity of the spectacle which this
nebula offers as it enters the field of view of a telescope, fixed in
right ascension, by the diurnal motion, ushered in as it is by so
glorious and innumerable a procession of stars, to which it forms a sort
of climax, and in a part of the heavens otherwise full of interest.'
Another large bright nebula (called 30 Doradus), also in the Southern
Hemisphere, is composed of a series of loops with intricate windings
forming a kind of open network against the background of the sky which
it adorns. Sir John Herschel describes it as one of the most
extraordinary objects in the heavens.
The 'Crab' Nebula in Taurus, the 'Horse-Shoe' Nebula in Sobieski's
Shield, and the 'Dumb-Bell' Nebula in Vulpecula are remarkable objects,
but the assistance of a powerful telescope is required to bring out
their distinctive features. The 'Crab' Nebula is partially resolvable
into stars; the other two are believed to be gaseous.
The largest and most remarkable of all the nebulae is that known as the
Great Nebula in Orion, which was discovered and delineated by Huygens in
the middle of the seventeenth century. It is perceptible to the naked
eye, and when viewed with a glass of low power can be seen as a circular
luminous haze surrounding the multiple star Theta Orionis--one of the
stars in the Giant's Sword, and which is of itself a remarkable object.
The most conspicuous part of the nebula bears a slight resemblance to
the wing of a bird; it consists of flocculent masses of nebulous matter
possessing a faint greenish tinge. Sir John Herschel compared it to a
surface studded over with flocks of wool, or to the breaking up of a
mackerel sky when the clouds of which it consists begin to assume a
cirrous appearance. Its brightest portion is occupied by four
conspicuous stars, which form a trapezium; around each there is a dark
space free from nebulosity, a circumstance which would seem to indicate
that the stars possess the power either of absorbing or of repelling the
nebulous matter in their immediate vicinity. When observed with a
powerful telescope, this nebula appears to be of vast dimensions, and,
with its effluents, occupies an area of 4 deg. by 5-1/2 deg.. Irregular
branching masses, streams, sprays, filaments, and curved spiral wreaths
project outward from the parent mass, and become gradually lost in the
surrounding space. This object remained for long a profound mystery; no
telescope was capable of resolving it, nor was it known what this
'unformed fiery mist, the chaotic material of future suns,' was, until
the spectroscope revealed that it consists of a stupendous mass of
incandescent gases--nitrogen, hydrogen, and other elementary substances,
occupying a region of space believed by some to equal in extent the
whole stellar system to which our Sun belongs.
In the Southern Hemisphere, near to the pole of the equator, are two
nebulous clouds of unequal size; the larger having an area about four
times that of the smaller. They are known as the Magellanic Clouds,
having been called after the navigator Magellan. Both are visible on a
moonless night, but in bright moonlight the smaller disappears. Sir John
Herschel, when at the Cape of Good Hope, examined those objects with his
powerful telescope. He described them 'as consisting of swarms of stars,
globular clusters, and nebulae of various kinds, some portions of them
being quite irresolvable, and presenting the same milky appearance in
the telescope that the nebulae themselves do to the naked eye.' These are
believed to be other universes of stars sunk in the profound depths of
space, our knowledge of their existence being dependent upon the faint
nebulous light which left them, perhaps, several thousand years ago.
[Illustration: GREAT NEBULA IN ORION]
The description of the various kinds of nebulae leads us to consider what
is called the Nebular Hypothesis. That the stars and solar system had at
some time in the past a beginning, is as much a matter of certainty as
that they will at some future time cease to be. Stars, like organic
beings, have their birth, grow and arrive at maturity, then decline into
a state of decrepitude, and finally die out. The duration of the life of
a star, which may be reckoned by millions of years, depends upon the
length of time during which it can maintain a temperature that renders
it capable of emitting light. By the constant radiation of its heat into
space, a condition of its constituent particles consequent upon the
gradual contraction of its mass will ultimately occur, which will result
in the exhaustion of its stores of thermal energy, the extinction of its
light, and the reduction of what was once a brilliant orb to the
condition of a mass of cold, opaque, inert matter. Inquiries as to the
origin of the stars have led scientific men to conclude that they have
been evolved from gaseous nebulae, and these have therefore been regarded
as indicating the earliest stage in the formation of suns and planets.
It is believed that the condensation of those attenuated masses of
luminous matter into stars is capable of accounting for the generation
and formation of all the shining orbs which enter into the structure of
the starry heavens. In the evolution of a 'cosmos out of a chaos' we
should expect to find stars presenting every stage of development--some
in an embryo state and others more advanced; stars in full vigour and
activity, stars that have passed the meridian of life, and stars in a
condition of decay and on the verge of extinction. The observations of
astronomers have led them to conclude that this condition of 'youth and
age' exists among the stellar multitude; but the characteristics by
which it is distinguished are neither very obvious nor reliable.
The nebular theory is incapable of proof or demonstration; but modern
discoveries tend to support the accuracy of its conclusions, and its
principles have now been adopted by the majority of philosophic
thinkers. The physical changes which are going on in the nebulae towards
stellar evolution, or in fully formed stars towards dissolution, are so
slow that the life of an individual, or even the historical records of
the past, are incapable of furnishing any evidence of alteration in
their condition. A period of time infinitely greater than what has
elapsed since the birth of science must pass before anything can be
known of the life history of the stars; indeed, the allotted span of
man's existence on this planet may have terminated ere the evolution of
a large nebula into a star cluster can have taken place.
The nebular hypothesis was first propounded by Kant, who suggested that
the sun and planets originated from a vast and diffused mass of cosmical
matter. This theory was afterwards supported by Herschel and by the
great French astronomer Laplace. As a result of close and continued
observation of the different classes of nebulae, Herschel arrived at the
conclusion that there exists in space a widely diffused 'shining fluid,'
of a nature totally unknown to us, and that the nebulosity which he
perceived to surround some stars was not of a starry nature. He further
adds that this self-luminous matter 'seemed more fit to produce a star
by its condensation than to depend on the star for its existence.' His
sagacious conclusion with regard to the non-stellar nature of this
nebulous matter was afterwards confirmed by the spectroscope; for at
that time it was believed that even the faintest nebulae were
irresolvable star clusters.
In 1811 Herschel read a paper before the Royal Society in which he
propounded his famous nebular hypothesis, and stated his reasons for
believing that nebulae, by their gradual condensation, were transformed
into stars. Having assumed that there exists a highly attenuated
self-luminous substance diffused over vast regions of space, he
endeavoured to show that by the law of attraction its particles would
have a tendency to coalesce and form aggregations of nebulous matter,
and that each of these, by the continued action of the same force, would
gradually condense and ultimately acquire the consistence of a star. In
the case of large irregular nebulae, numerous centres of attraction would
originate in the mass, round which the nebulous particles of matter
would arrange themselves; each nucleus, when condensation had been
completed, would become a star, and the entire nebula would in this
manner be transformed into a cluster of stars. Herschel believed that he
could trace the different stages of nebular condensation which result in
the evolution of a star. In large, faintly luminous nebulae the process
of condensation had only commenced; in others that were smaller and
brighter it was in a more advanced stage; in those that contained nuclei
there was evidence of nascent stars; and, finally, there could be seen
in some nebulae minute stellar points--new-born suns--interspersed among
the haze of the transforming mass. By this theory Herschel was able to
account for the phenomena associated with nebulous stars and the
supposed changes which were observed in some nebulae. The nebular
hypothesis as described by Herschel was not received with much favour,
nor did it unsettle much the belief that all nebulae were vast stellar
aggregations, and that their cloudy luminosity was a consequence of the
inadequacy of telescopic power to resolve them into their component
stars. Laplace, who was highly gifted as a geometrician, demonstrated
how the solar system could have been evolved in accordance with
dynamical principles from a slowly rotating and slowly contracting
spheroidal nebula. The rotatory motion of a nebula, in obedience to a
well-known mechanical law, increases as its density becomes greater, and
this goes on until the tangential force at the equator overcomes the
gravitational attraction at its centre. When this occurs, a revolving
ring of nebulous matter is thrown off from the parent mass, and by this
means equilibrium is restored between the two forces. As the rotatory
velocity of the nebula continues to increase with its contraction,
another ring is cast off, and in this manner a succession of revolving
rings may be detached from the condensing spheroid; each newly-formed
ring being nearer to the centre of the contracting mass and revolving in
a shorter period than its predecessor. In the evolution of our system,
the central mass of the nebula became the Sun and each of the revolving
rings, by their condensation into one mass, formed a planet. In a
similar manner, though on a diminished scale, the elementary planets,
whilst in a nebulous state, parted with annular portions of their
substance, out of which were evolved their systems of satellites. This
theory furnished a plausible reason, which was capable of explaining how
the orbs which constitute the solar system came into existence, and,
though hypothetical, yet the manner in which it accounted for the
orderly and symmetrical genesis of the system rendered it attractive and
fascinating to scientific minds.
The evidence in support of the nebulous origin of the solar system, if
not conclusive, is of much weight and importance. The remarkable harmony
with which the orbs of the system perform their motions is strongly
indicative of their common origin and that their evolution occurred in
subordination to the law of universal gravitation. The following are the
characteristic points in favour of this theory:--
1. All the planets revolve round the Sun in the same direction, and they
all occupy nearly the same plane.
2. Their satellites, with the exception of those of Uranus and Neptune,
perform their revolutions in obedience to the same law.
3. The rotation on their axes of the Sun, planets, and satellites is in
the same direction as their orbital motion.
Between the orbits of Mars and Jupiter there revolves a remarkable group
of small planets or planetoids. On account of the absence of a planet in
this region, where, according to the laws of planetary distances, one
ought to be found, the existence of those small bodies was suspected for
some years prior to their discovery. The first was detected by Piazzi at
Palermo in 1801; two others were discovered by Olbers in 1802 and 1807,
and one by Harding in 1804. For some time it was believed that no more
planetoids existed, but in 1845 a fifth was detected by Hencke, and from
that year until now upwards of 300 of those small bodies have been
discovered. Their magnitudes are of varied extent; the diameter of the
largest is believed not to exceed 450 miles, and that of the smaller
ones from twenty to thirty miles. It was surmised at one time, when only
a few of those bodies were known, that they were the fragments of a
planet which met with some terrible catastrophe; but since the discovery
of so many other planetoids this theory cannot be maintained. According
to the nebular hypothesis, these bodies are the consolidated portions of
a nebulous ring which remained separate instead of having coalesced into
one mass so as to form a planet. The uniform condensation of the ring
would result in the formation of a multitude of small planets similar to
what are found between the orbits of Mars and Jupiter. In Saturn's ring
we have a remarkable instance of annular consolidation in which the form
of the ring has been preserved. The ring is believed to consist of
myriads of minute bodies, each of which travels in an orbit of its own
as it pursues its path round the planet; the close approximation and
exceeding minuteness of those moving objects create the appearance of a
solid continuous ring.
Though, by means of the nebular hypothesis, it is impossible to explain
all the phenomena associated with the motions of the orbs which enter
into the structure of the solar system, yet this does not detract much
from the merits of the theory, the fundamental principles of which are
based upon the evolution of the solar system from a rotating nebula.
The retrograde motions of the satellites of Uranus and Neptune, the
velocity of the inner Martian moon, and other abnormalities in the
system, have not as yet been explained, but doubtless there are reasons
by which those peculiarities can be accounted for if they were only
known, '_felix qui potuit cognoscere causas omnium rerum_.'
No attempt has been made to supplant the nebular hypothesis by any other
theory of cosmical evolution. Modern investigations and discoveries have
strengthened its position, and at present it is the only means by which
we can account for the existence of the visible material universe by
which we are surrounded.
In the days when Milton lived--three hundred years ago--the nocturnal
heavens presented the same appearance to an observer as they do at the
present time. The stars pursued their identical paths, and looked down
upon the Earth with the same aspect of serene tranquillity, regardless
of the vicissitudes which affect the inhabitants of this terrestrial
sphere. The constellations that adorn the celestial vault duly appeared
in their seasons,
and in the ascending scale
Of Heaven the stars that usher evening rose.--iv. 354-55.
The winter glories of Orion, the scintillating brilliancy of Sirius, and
the spangled firmament, bearing no impress of change or variation which
would lead one to conclude that the heavens were other than eternal,
attracted then, as now, the admiration of beholders.
Apart from the orbs which constitute the solar system, little was known
of the sidereal heavens beyond the visual effect created by the
nocturnal aspect of the star-lit sky. Though ancient philosophers
hazarded an opinion that the stars were suns, they received but scant
attention from early astronomers, by whom they were merely regarded as
convenient fixed points which enabled them to determine with greater
accuracy the positions of the planets and the paths traced out by them
in the heavens. The Ptolemaists, who believed in the diurnal revolution
of the spheres, assigned to the stars a very subordinate place in their
cosmology, which was the one adopted by Milton; and although Copernicus
relegated them to their proper location in space, yet he had no clear
conception of a universe of stars. Tycho Brahe, who declined to accept
the Copernican theory, disbelieved that the stars were suns, and
Galileo, who discovered the stellar nature of the Milky Way, remarked
that the stars were not illumined by the Sun's rays in the same manner
that the planets are, but expressed no opinion with regard to their
physical constitution. It is only within the past fifty years that proof
has been obtained of the real nature of the stars. By the spectroscopic
analysis of their light it has been ascertained that the elements of
matter which enter into their composition exist in a condition similar
to what is found in the Sun. The stars are therefore suns, many of them
surpassing in magnitude and brilliancy the great luminary of our
system.
Though Milton makes frequent allusion to the magnificence of the starry
heavens, we have no evidence that he regarded the stars as suns, nor
does he refer to them as such in any part of his poem.[12] What
impressed him most was their number and brilliancy, to which reference
is made in the following passages:
About him all the Sanctities of Heaven
Stood thick as stars.--iii. 60-61.
And sowed with stars the Heavens thick as a field.--vii. 358.
Amongst innumerable stars, that shone
Stars distant, but nigh hand seemed other worlds.--iii. 564-65.
her reign
With thousand lesser lights dividual holds,
With thousand thousand stars, that then appeared
Spangling the hemisphere.--vii. 381-84.
Milton describes the number of the fallen angels as
an host
Innumerable as the stars of night.--v. 744-45,
and the attention of Satan is directed by the archangel Uriel to the
multitude of stars formed from the chaotic elements of matter:
Numberless as thou seest, and how they move;
Each had his place appointed, each his course;
The rest in circuit walls this universe.--iii. 719-21.
Though Milton was doubtless familiar with the leading orbs of the
firmament and knew their names, and the constellations in which they are
situated, yet he makes no direct allusion to any of them in his poem.
Neither Arcturus, which is mentioned in the Book of Job, nor Sirius,
which attracted the attention of Homer, who compared the brightness of
Achilles' armour to the dazzling brilliancy of the dog-star, finds a
place in 'Paradise Lost.' And yet the superior magnitude and brilliancy
of some stars when compared with those of others did not escape Milton's
observation when, in describing the lofty eminence of Satan in heaven,
prior to his fall, he represents him as
brighter once amidst the host
Of angels than that star the stars among.--vii. 132-33.
There is but one star to which Milton makes individual allusion, and,
though not of any conspicuous brilliancy, yet it is one of much
importance to astronomers--
the fleecy star that bears
Andromeda far off Atlantic seas
Beyond the horizon.--iii. 558-60.
This is Alpha Arietis, the first point in the constellation of that
name, which signifies the Ram, and from which the right ascensions of
the stars are measured on the celestial sphere. In the time of
Hipparchus the ecliptic intersected the celestial equator in Aries,
which indicated the commencement of the astronomical year and the
occurrence of the vernal equinox; but, owing to precession, this point
is now 30 deg. westward of Aries and in the constellation Pisces. The star
was called Hamal by the Arabs, signifying a sheep, and the animal is
represented as looking backwards. Manilius writes:--
First Aries, glorious in his golden wool,
Looks back and wonders at the mighty Bull.
Aries is associated with the legend of the Golden Fleece, in quest of
which Jason and his valiant crew sailed in the ship 'Argo.' In the
autumn, Andromeda is situated above Aries, and would seem to be borne by
the latter, which accounts for Milton's description of the relative
positions of those two constellations.
Milton alludes to the starry sphere in several passages in his poem, and
also mentions the starry pole above which he soared in imagination up to
the Empyrean or Heaven of Heavens. His contemplation of the Galaxy must
have impressed his mind with the magnitude and extent of the sidereal
universe, for he was aware that this luminous zone which encircles the
heavens consists of myriads of stars, so remote as to be incapable of
definition by unaided vision. Milton's description of this vast
assemblage of stars is worthy of its magnificence, and the purpose with
which he poetically associates this glorified highway testifies to the
sublimity of his thoughts and to the originality of his genius. In those
parts of his poem in which he describes the glories of the celestial
regions, and instances the beautiful phenomena associated with the
individual orbs of the firmament, we are able to perceive with what
exquisite delight he beheld them all.
The invention of the telescope, and the important discoveries made by
Kepler, Galileo, and Newton in the seventeenth century, were the means
of effecting a rapid advance in the science of astronomy; but that
branch of it known as sidereal astronomy was not then in existence. The
star depths, owing to inadequate telescopic power, remained unexplored,
and the secrets associated with those distant regions were inviolable,
and lay beyond the reach of human knowledge. The physical constitution
of the stars was unknown, nor was it ascertained with any degree of
certainty that they were suns. The knowledge possessed by astronomers in
those days was but meagre compared with what is now known of the
sidereal heavens. Milton's astronomical knowledge, we find, was
commensurate with what was known of the stellar universe, and this he
has conspicuously displayed in his poem.