GREAT STARS OF THE SOUTH
SPICA FORMALHAUT
ANTARES SIRIUS
WITH the exception of the stars in the constellation of Orion,--Spica,
Antares, Formalhaut and Sirius are the only stars of the first magnitude
south of the celestial equator which are visible from any point in the
United States. The Orion stars are winter stars and will be taken up in
the chapter to follow, but these four stars, each of which in turn looms
lonesomely in the south, are representatives of the seasons, and their
very names, Spica, Antares, Formalhaut and Sirius, bring to mind
successively, spring, summer, autumn and winter.
Spica, the "Spring Star," rises at sunset on the 10th of April and
crosses the meridian during the early evenings of April, May and June.
Its beautiful silvery-white flame first appears just a little south of
east and it takes only 5 hours and 25 minutes to cover half of its arc
across the sky. It is then a little less than half way up from the
horizon and hangs on the same curve from the Big Dipper's handle as
Arcturus.
Antares rises at sunset on the first of June and passes the meridian
early in the evening during June and July. It rises farther south of
east than Spica and takes only 4 hours and 23 minutes to reach the
meridian. It is then only one-quarter of the way up from the horizon.
Being a brilliantly red star in a conspicuous anchor-like constellation
near the Milky Way, it is very easy to locate.
Formalhaut rises at sunset about the 10th of October and reaches the
meridian about 4 hours later. It first appears in the southeast and
skims in a short arc closer to the horizon than any other first
magnitude star.
Sirius rises in the southeast about 9 o'clock on the first of December,
but anyone wishing to see this magnificent star during the summer months
should look toward the east about 4 o'clock in the morning on the 16th
of August. In 5 hours and 3 minutes this star reaches the meridian,
one-third of the way up from the horizon. Sirius is the largest and
loveliest star in the sky, possessing such a vivacious character
combined with a sparkling, diamond-like beauty, that it is a delight to
every eye that beholds it.
SPICA
[Figure 95]
The constellation of Virgo, in which Spica is found, is easily
recognized by its brilliant white star and its large V or corner of five
stars which marks off the upper portion. The Arabian astronomers called
the corner "The Kennel" or "The Retreat of the Howling Dog." Just beyond
the Kennel gleams the star-dust on Berenice's Hair, and above this
sprinkling of minute stars, howl the furious hounds of Boötes
struggling madly to pounce upon the Bear.
A most remarkable nebulous region lies within the triangular corner of
Virgo, although the nebulæ are very faint and only visible through a
large telescope. Nebulæ as a class are found in abundance in the
vicinity of the north pole of the galaxy, which lies in the
constellation Coma Berenices, this corner alone containing almost 300,
although they are rarely found along the path of the Milky Way.
The yellow 3rd magnitude star on the upper end of the corner in Virgo
has for many ages been called Vindemiatrix, which means
"Grape-Gatherer."
[Figure 96]
It is believed that the star was given this curious name because it was
observed to rise before the sun in the season in which grapes ripened.
Vindemiatrix has a minute distant companion of a deep red color. The
star at the other end of the corner has the interesting name of
Zavijava, while the point is noted as a binary having a period of 185
years.
[Figure 97]
Spica, the "jewel of the Virgin," is best located by dropping an
imaginary line through Arcturus from the handle of the Big Dipper.
It rises about an hour later than Arcturus (who first appears at sunset
during the latter part of March), and travels in a curve through the
south.
[Figure 98]
These two stars contrast beautifully as they swing through the sky like
gold and silver globes of fire strung on an invisible thread. A tale
current among ancient people was that Virgo, the Virgin, was once
Astræa, Goddess of Purity and Justice, who lived on earth during the
Golden Age when all men were happy. During the Silver Age contentment
still prevailed and the Gods lingered although men were less perfect and
the world less tranquil. When the Bronze Age was ushered in men became
so inferior that the work of Astræa's office was ignored and she fled
in sorrow to the sky.
"Even so long as the earth still nurtured the Golden Race, she had her
dwelling on earth. But with the Silver Race only a little and no longer
with utter readiness did she mingle--
"When the Bronze Race was born she loathed them for they forged the
sword of the highwayman, ate the flesh of the plowing ox and engaged in
strife and discord."
--_Aratus_ (_Trans._ C. R. MAIR).
Somehow the goodness and purity of Astræa were incorporated in one
beautiful star called Spica, and this star shone with such exceeding
whiteness that the whole constellation became Virgo, the Virgin. The
pictures drawn on the maps vision a goddess with wings carrying a palm
branch in one hand and an ear of wheat in the other. In some of the
older maps, the goddess carries a balance or a pair of golden scales
with which to weigh the fate of mortals, but this is now a separate
constellation--Libra, the Scales--lying to the east of Virgo. In
classic days, the two bright stars which mark the Scales were on the
claws of the Scorpion which were then pictured as more extended.
The ancient people worshiped the constellation of Virgo with its
beautiful white star, and, even as a quiet prayer may be said in music
instead of in words, the purity of Spica seemed to glow like a
benediction upon their revering hearts.
Even to the modern world, the springtime loveliness of this large and
beautiful star is refreshing. But we are wont to gaze upon it more with
awe than reverence for science tells us that it is not only one white
star but two, the mass of each being much greater than that of our sun.
These two stars are only 11,000,000 miles apart and whirl around their
common center of gravity in the amazingly short period of only four
days!
Such is the jewel found on the Virgin's ear of wheat, although the myths
do not all agree that Virgo is Astræa.
"Whether she be the daughter of Astræus, who, men say, was of old the
father of the stars, or the child of other sire, untroubled be her
course."
--_Aratus._
However, they all do seem to agree that the constellation is connected
in some way with the thought of harvests.
Virgo was early identified as the Egyptian Isis who dropped an ear of
wheat as she fled from the monster Typhon when he appeared around the
Nile. As a result the wheat was scattered in a wide path along the
heavens which is now called the Milky Way. Among other characters, Virgo
has been regarded as Ceres, the Goddess of the Harvests, and even as
Ceres' daughter Proserpine. Plutarch seems to think that the Greeks are
indebted to the Egyptians for their story of Ceres. Thus the Egyptian
Isis would be Ceres, or Demeter. Isis also taught the use of corn which
once stood neglected in the fields. The story of Ceres and Proserpine
is particularly beautiful and deserves a place in every one's
thoughts. One cannot have too many associations as he gazes at the
starry skies, for each bit of even ancient gossip added to modern facts
increases the pleasure in knowing different stars. This is particularly
true if one does not own a telescope of any kind, indispensable as it
may be to an astronomer.
The temple of Ceres, or Demeter, meaning "Mother Earth" (that is, not
the whole solid earth, but the portion that produces vegetation), stands
in the sacred city of Eleusis, on the Thracian plain, and all men who
earn their living by the soil come here to do her honor. This temple was
built on the spot where the Goddess met Triptolemus and taught him the
use of grains, also how to plow, sow the seeds and gather the crops
after they had ripened. Triptolemus then went forth and taught the
nations of the world.
One day while Ceres was watching the harvests, Proserpine, her lovely
daughter, disappeared.
"While like a child with busy speed and care
She gathers lilies here, and vi'lets there;
While first to fill her little lap she strives,
Hell's grizzly monarch at the shade arrives.
See's her thus sporting on the flow'ry green
And loves the blooming maid as soon as seen."
"Swift as a thought he seized the beauteous prey
And bore her in his sooty car away."
--_Ovid's Metamorphoses_ (MAYNWARING'S Trans.)
Pluto, it seems, had come above the ground to survey the surface of the
Sicilian land, for the roof of his kingdom had been considerably shaken
on account of the struggles of the giant Typhon confined beneath the
roots of Mount Etna. Poets claim that no sooner had the Underground God
appeared than Cupid, the mischievous son of Venus, pulled a gold-tipped
arrow from his sheath, and laughing gleefully, shot the gloomy
monarch in the heart.
Ceres, in the meantime, nearly frantic with grief, searched over land
and sea for her lost daughter, and when night fell, so that her search
might not be hindered, she tore up young pine trees by the roots and
dipped them in the fires of Mount Etna. She could not eat, saying (as
Tennyson puts it) that the "nectar smack'd of hemlock" and the "rich
ambrosia tasted aconite," while ancient poets claim that neither Aurora,
the Dawn, nor Hesperus, the Evening Star, ever saw her rest. Yet
unweakened by fatigue and lack of sustenance, the goddess turned to the
earth and forbade it to bear until Proserpine was returned to her.
When Ceres discovered that the King of the somber, joyless region under
the ground had carried off Proserpine and made her the Queen of his
Shades, she left the home of the gods in anger and went to live among
mankind. Jupiter at last becoming fearful for the fate of man if earth
no longer bore fruit or grain, sent Mercury down to inquire of Pluto if
there was any hope of Proserpine's return. The Fates sent reply that if
Proserpine had not tasted the pomegranate, the food of death, she could
not be detained, otherwise she must remain forever. Ascalaphus then
stepped forward and said that he had seen the Queen eat some of the
seeds of this fruit,--for which tattling he was turned into a screech
owl. Jupiter, pitying Ceres in her disappointment, succeeded in
effecting a compromise by inducing his brother to allow Proserpine to
spend six months of every year with her mother. This, the Greeks say, is
the cause of summer and winter.
When Proserpine appears, Ceres commands the seeds, also, to force their
way above the ground, the orchards become bright with a wealth of
blossoms and the fields fresh with sprouts and vines. Ceres then is
happy and the world a busy, beautiful place in which to live, but when
Proserpine leaves, she cares not what happens, and the earth grows
withered and drear. Of all the myths, Virgo seems the most charming when
identified as Proserpine. Watch for the white flame of Spica as it rises
just south of east on the 10th of April, for Spica shines on the ear of
wheat in the hand of Ceres' daughter and is a symbol of the coming
spring.
ANTARES
[Figure 99]
The red star Antares lies on the heart of the Scorpion and stands out
conspicuously with a bright star on either side.
In Greek legend this is the same Scorpion which so frightened Phæthon,
rash child of the Sun-god, when he was driving his father's chariot
along the zodiac. The headstrong youth had experienced trouble enough in
passing by the ferocious Nemean Lion, and he was just getting a free
breath while driving by the Virgin and the Scales when he came to this
terrifying creature sprawled along and almost blocking the sky path.
Unable to longer control either himself or his excited horses, Phæthon
turned the steeds aside and blazed a new pathway, which soon grew cold
and left a gray ash across the sky. The strip burned out by the
scorching heat of the chariot may still be seen at night and is claimed
by some to be the Milky Way.
There is still another legend which tells how the scorpion came to be a
constellation. In ancient Greece there was once a mighty hunter named
Orion. Armed with only a club, this powerful and handsome giant was able
to conquer any beast in the world but, unfortunately, he boasted so
continuously that Juno resolved to teach him a lesson. One day while he
was battling with a monster in a swamp, a poisonous scorpion
slipped up and stung him on the heel. The wound proved fatal, although
he was afterward given a constellation as if in atonement for the rather
mean advantage taken of so brave a hunter.
"The vast Orion thus he doomed to die,
And fix'd him, his proud trophy, in the sky."
--_Lucan's Pharsalia._
But the scorpion was also honored in the same way, only he travels
across the sky in the summer months while Orion is seen during the
winter. Thus the two are considerately placed so that they do not shine
above the earth in the same season.
"And so 'tis said that when the Scorpion comes
Orion flies to the utmost ends of the earth."
--_Aratus._
The constellation of the Scorpion lies southeast of Libra, the Scales,
and is the ninth and most brilliant in the zodiac. The gigantic and
clearly marked star design on his figure shows that the creature's head
and outstretched claws extend upward and toward the west; the upraised
tail, curving through the Milky Way and close to the horizon, lies south
and eastward; while his feet touch the fainter stars to the right and
left. In the vicinity of his heart lies a star so large and red and
beautiful that it was named "Antares," which means "the rival of Ares"
(the planet Mars). This star so impressed the ancient people of Greece
that they built a temple in honor of it, where they might gaze upon it
in solitude and worship it as if it were enthroned. This temple is one
of the oldest found in Greece.
Pease, with the aid of the interferometer on the great 101-inch
telescope on Mount Wilson, has measured the diameter of Antares and has
found it to be a very enormous red sun. This figure taken in connection
with the best determined value of its distance, indicates that its
diameter is _four hundred million miles_! The volume of this star is
therefore about twenty-five million times as great as the volume of our
sun. As far as we know, this is the largest star. This is surely most
interesting. We might have imagined these gloriously tinted stars as
small-sized novelties scattered about the heavens for our special
edification--certainly we did not expect to find that some of them were
so tremendously large that they would pass by our little golden orb as a
speck of incandescent sand.
[Figure 100: THE BATTLE OF ORION, THE GIANT, AND TAURUS, THE BULL.]
Not only is Antares of interest because of its great size and charming
color but it also possesses a companion star of the vividest shade of
green. This companion was first noted during an occultation in 1819,
quite amazing its observer by sliding out from behind the moon just
before the large red star emerged and dimmed its light by its powerful
ruddy rays. The green-hued star is very tiny in comparison to Antares
and may only be seen with the aid of a 5- or 6-inch telescope. Under
good atmospheric conditions it is a very beautiful object.
The flame-red sun Antares beside its woodsy-green companion is one of
the most impressive color combinations among the stars. Imagine living
on a planet whose orbits encompassed such ostentatious stars! A green
sunrise with a livid sky and a red sunset with a scarlet one—then a
red sunrise and a green sunset--if colors affect one the way it is
sometimes said that they do, the inhabitants of such a planet might live
through "red hours" and "green hours" like "Dr. Jekylls" and "Mr.
Hydes."
What a surprise to the eye and a delectable bit for the imagination are
the blue, gold, green, rose, lilac, purple and other fires in the
sun-lit sky. Here is something "as rare as a day in June." It would seem
as if the whole solar system were enchanted if we might visit the
planets of a white and sapphire blue sun, for instance, or those of one
of topaz-yellow and heliotrope hue. On the other hand it might seem
beyond the bounds of reason to an inhabitant of a planet with a
dark blue sun that a ray of white light contains the whole seven primary
colors and that these colors are separately and in combination absorbed
by the different objects on such a planet as our earth, permitting us to
observe a wonderful exhibition of tints and colors, gayety, shade and
brightness. If he, in his semi-dark blueness, could possibly visualize
such a marvel as this, he surely would be well-nigh overwhelmed with the
wonder of it. Perhaps our sun was the only star of the millions of stars
in our Universe--(or in the innumerable Universes which drift in space
beyond the island of our Universe)--that was able to produce planets
that could bear life; and yet again, since the spectroscope has proved
that our sun is constituted like many another star in the heavens,
perhaps these other stars, like our sun, also have planets. At least it
is reasonable and rather exhilarating to think about it.
All the brilliant red stars are young and in the giant stage of their
career but the faint red stars are dwarfs and on their decline. The
dwarf red stars are believed to be cooling for they possess chemical
combinations only possible in a decreasing temperature relatively low
for stars. This must mean that such stars are growing old, for metallic
vapors are never found in stars that are young.
[Figure 101]
In a still later stage, these metallic vapors condense and form a solid
crust. About 500 red stars have already been observed but they are all
at a distance vastly remote from the territory of our sun. Antares,
however, is among the most youthful of the giant red stars and will
gradually rise in temperature and become brilliantly blue during the
next few thousands of millions of years.
Halfway between Antares and Akrab (β on the end of the upper claw),
lies a very rich and condensed cluster of stars. This cluster, which is
one of the finest known, may be easily seen in a small telescope. On the
eastern side of the cluster is a dark nebula. Akrab is a triple star of
the 2nd, 4th and 10th magnitudes. The little star 2 degrees east of
Akrab is of the 4th, 5th, 7th and 8th magnitudes and is claimed by some
to be the most beautiful quadruple in the heavens. Many other
interesting stars may be seen around this conspicuous figure with a
2½- or 3-inch telescope, and a handy little reference book for the amateur
fortunate enough to possess such a telescope is William Tyler Alcott's
"In Starland with a Three-Inch Telescope."
FORMALHAUT
[Figure 102]
Formalhaut is called the "Fish's Mouth" star because it is supposed to
shine on the mouth of Piscis Australis, the Southern Fish. This Fish is
represented in the star-maps as holding open its mouth in utter
contentment while a long line of small, glittering stars wash down in a
stream of water. This water flows from the Urn of Aquarius, the
Water-bearer, who stands just below the head of Pegasus, the Winged
Horse. The Urn is formed by a little Y of 3rd and 4th magnitude stars,
and, to the Egyptians, was an emblem of the rainy season.
"Rolls from Aquarius' vase a limpid stream
Where numerous stars like sparkling bubbles gleam."
--_Aratus._
The Southern Fish must not be confused with the two tied fishes of the
constellation of Pisces, known as the "Northern Fish," which lie
to the east of the Waterbearer's Urn. This region of the sky has been
called the "Sky Sea," for not only does it contain three fishes but also
Cetus, the Whale, Delphinus, the Dolphin, and Capricornus, the Sea-goat.
[Figure 103]
The three fish and the Seagoat were placed in the sky to commemorate the
adventures of the Goddess Venus, the little God Cupid and the God Pan
with the terrible fire-breathing monster Typhon. When Typhon appeared
with a deafening roar, shaking his head and belching fire, the immortals
fled in a panic before him, and when Venus and Cupid and Pan jumped into
a river, they were transformed into two fish and a Sea-goat.
[Figure 104: The constellations which border the "Sky Sea." All of these
stars are not in view at the same time.]
The Southern Fish is connected in some way in the story but just how is
not quite clear. Northwest of Aquarius lies the region of birds, while
beyond the "Sea" to the southeast is the hunting scene of the giant
Orion. The River Eridanus may also be seen flowing from a star near
Rigel, on the foot of Orion, to a point on the shore of the "Sea."
Formalhaut rises in the south at twilight about the 10th of October and
wanders westward in a small arc above the horizon. It is visible such a
short time that it is said that it comes "when the leaves begin to fall
and goes while they are still falling." This star rises in the south at
the same time that Capella rises in the northeast, but an easier way of
locating it may be found by estimating two-thirds of the distance across
the sky from the outside stars in the bowl of the Big Dipper. It also
lies almost exactly in a straight line with the two stars on the west
side of the great Square of Pegasus at a distance equal to 3⅓ times
the distance between them and the southernmost of the two.
SIRIUS
[Figure 105]
If all the diamonds in the world were melted into one huge, magical
jewel, its sparkling brilliance would pale beside Sirius, the diamond of
the heavens.
This wonderful, iridescent beauty, fresh as a prismatic ice-flame, if
such a thing might be, is best appreciated on a clear, cold winter night
when the little stars swarm out like fire-flies and the large stars burn
like Aladdin gems of frost and fringing fire.
The ancient Greeks, strange to say, dreaded the sight of this beautiful
star, for they not only imagined that its "burning breath" caused the
unhealthy and oppressive heats of summer but that it was directly
responsible for their parched grass and blighted corn, their mad dogs
and raging fevers!
The unpopularity of this star was due to the fact that during the
hottest days of July it rose just before the sun and preceded that
luminary all day long in his pathway through the heavens. Not knowing
that Sirius lay many millions of millions of miles beyond our solar
system, they quite naturally supposed that his bright rays blended with
those of the sun, greatly intensifying the heat. Thus Sirius caused the
hottest season of the year and all the dried fields, mad dogs, plagues
and fevers were attributed to its malignant influence. Since the huge
star belonged to the constellation of Canis Major, the Great Dog, it was
called the "Dog Star" and these hot, sultry days, the "dog-days." The
dog-days lasted for about 40 days, extending from 20 days before the
heliacal rising of the Dog-star Sirius to 20 days after. Owing to the
precession of the equinoxes, the heliacal rising of Sirius is different
from what it was to the ancients and the dog-days are now counted from
the 3rd of July to the 11th of August.
Unlike the Greeks, the ancient Egyptians held Sirius in the highest
esteem and built splendid temples in its honor in the valley of the
Nile. J. Norman Lockyer has made an extensive study of Egyptian temples
and has described them most interestingly in his book "The Dawn of
Astronomy." During his explorations he found seven temples which were
constructed solely to guide the light of Sirius through an opening in
the side of the temple, down a long hallway to a point on the central
altar. Olcott in "Star Lore of All Ages" visualizes the following
beautiful scene in the most notable of these, the temple of Isis at
Denerah:
"Here the rising beams of Sirius flashed down a long vista of massive
pylons and illuminated the inner recesses of the temple. What a
wonderful scene there must have been enacted within that darkened
edifice, when, in the presence of a vast multitude silent in meditation,
there suddenly appeared a gleam of silver light, that laved the marble
altar in a refulgence born of the infinite, a beam, altho' the watchers
knew it not, that had started on its earthward journey 8½ years before
it greeted their eyes."
Why did the Egyptians reverence this star and hold it sacred while the
ancient Greeks watched the same heliacal rising and vehemently denounced
it for journeying so close to the sun at a season when additional heat
was least desired? The Egyptians thought little about the heat, but with
the appearance of this star just before the rising of the sun they knew
that the season had arrived for the annual overflow of the Nile.
"Far in the south the daring waters rise,
As in disdain of Cancer's burning skies;
Thence, with a downward course, then seek the main,
Direct against the lazy northern wain."
--_Lucan's Pharsalia._
This heliacal rising of Sirius, which the Egyptians called Sothis, was
an event which needs must be heeded, for, having no calendars in those
ancient days, it served as a warning that the river would soon overflow
its banks and make a vast sea of the lowlands. It then behooved the
husbandmen and gardeners to act quickly, and move themselves and their
herds and flocks up to the dykes in a place of safety.
"Nile's redundant waters never rise
Till the hot Dog inflames the summer skies;
Nor to his banks his shrinking stream confines,
Till high in Heaven th' autumnal Balance shines."
--_Lucan's Pharsalia._
During the inundation the lowlands are so completely covered with water
that towns and villages rise like islands, while here and there are seen
the tops of groves and fruit-trees like shrubs on the surface of the
sea. This "yearly tribute of rains" which the Nile brings from other
countries, gives new life to the parched land of the Egyptians.
Herodotus, centuries ago, said that Egypt was the gift of this river,
for without it their country would be a part of a lifeless desert.
In the words of Amru, Egypt first appears as a dusty plain, then as a
fresh sea, and finally as a bed of flowers. To still better understand
why seven great temples were erected for Sirius, the "Nile Star," whose
constellation was sometimes called "the watch-dog on the Nile," let us
read Osborn's graphic description in "Monumental Egypt" of the
transformations resulting from the watering of the sands by the overflow
of the great river which the Egyptians guarded and held sacred.
"The Nile has shrunk within its banks until its stream has contracted to
half its ordinary dimensions, and its turbid, slimy, stagnant waters
scarcely seem to flow in any direction. Broad flats or steep banks of
black, unbaked Nile mud, form both shores of the river. All beyond is
sand and sterility; for the ham-seen or sand-wind of fifty days duration
has scarcely ceased to blow. The trunks and branches of the trees may be
seen here and there through the dusty, hazy, burning atmosphere, but so
entirely are their leaves coated with dust that at a distance they are
not distinguishable from the desert sand that surrounds them."
Then comes the inundation:
"Perhaps there is not in Nature a more exhilarating sight, or one more
strongly exciting to confidence in God, than the rise of the Nile. Day
by day, night by night, its turbid tide sweeps onward majestically over
the parched sands of the waste howling wilderness. Almost hourly, as we
slowly ascended it before the Etesian wind, we heard the thundering fall
of some mud bank, and saw by the rush of all animated Nature to the
spot, that the Nile had overleapt another obstruction, and that its
bounding waters were diffusing life and joy through another desert."
After the flood comes sowing time and the effects of it all are
exhibited:
"in a scene of fertility and beauty such as will scarcely be found in
another country at any season of the year. The vivid green of the
springing corn, the groves of pomegranate trees ablaze with the rich
scarlet of their blossoms, the fresh breeze laden with the perfumes of
gardens of roses and orange thickets, every tree and every shrub covered
with sweet-scented flowers."
No wonder that the appearance of Sirius was hailed with reverence when
its rising just before the sun meant also the rise of the life-giving
river and the prosperity of the inhabitants of Egypt! However, as
mentioned before, with the precession of the equinoxes, the heliacal
rising of Sirius has changed and its brilliant light no longer announces
the rising of the Nile.
Sirius is one of our nearest stars for its light requires only 8½ years
to reach the earth. Yet its nearness does not account altogether for its
quite exceptional brightness, for our sun at the same distance would
appear as a star of the 6th magnitude and be invisible to the unaided
eye. Only two stars, as far as has yet been discovered, lie closer to
the earth than Sirius. The second brightest star in the sky is Canopus,
visible from the southern hemisphere, but so far away that its distance
can scarcely be estimated.
Halley, a celebrated English astronomer born 1656, made the first
discovery of the relative motion of the stars when he noted that Sirius
had moved from the position assigned to it on Ptolemy's map of 150 A. D.
We have now reliable data for discussing the proper motion of about
10,000 stars. The proper motion of stars consists of a displacement in
various directions of the individual stars. Thus the configuration of a
constellation may slowly change, and, although many groups of stars all
travel in the same direction, there are also conspicuous instances where
they move in different directions. The Big Dipper and the Southern Cross
are two star groups whose stars are traveling along different courses
and after a period of time extending over thousands of years, the
'dipper' and the 'cross' effect of these two constellations will have
altogether disappeared.
For a while Sirius was believed to be traveling in a straight line, but
soon irregularities were discovered in the great star's motion, an
"undulatory progressive motion" on each side of a middle line. From a
knowledge of these oscillating movements, Bessel inferred that
Sirius must have an unseen companion attracting or pulling it as the two
stars traveled together around a common center of gravity. In 1862, Mr.
Alvan G. Clarke of New York detected this companion situated at an
angular distance of only 7" from Sirius,--about as far distant as Uranus
is from the earth. The larger star is only about twice as massive as its
companion but is 20,000 times brighter. The light that we see from
Sirius then comes from two stars which together radiate 48 times as much
light as the sun. Compared to Sirius, our sun is rather an inconspicuous
star, although Barnard gave us great satisfaction by discovering a
neighbor not much farther away than Sirius which gives out only
¹⁄₂₅₀₀ as much light as the sun!
Sirius, the "Dog Star," rests on the nose of the Great Dog, in the
constellation Canis Major, and may be found in a straight line from the
three evenly spaced stars in Orion's Belt. He was originally Orion's
hunting dog, and, as if to give atmosphere to a hunting scene in the
sky, Lepus, the Hare, has been placed on a constellation just in front
of Sirius and below the feet of Orion, where he is "pursued continually
through all time" by the Dog with the huge star.
A vividly red variable star glows in the constellation of Lepus, the
Hare. Every so often, this little star becomes radiantly red. This
additional light is caused by the star bursting explosively through the
layer of absorbent vapors which are smothering the life from its flames.
Some day this crimson star will flare and flicker for the last time and
its final ray be wafted to our earth--the Swan Song of a dying star.
About 9 o'clock during the first part of December, Sirius rises on its
pathway south of east, the brilliant beauty of its light adding to the
celestial scene like a torch among a thousand candles. This is true
though the month of December exhibits the loveliest assembly of stars to
be seen in all the year.
From December on into early spring, the Dog Star is the cynosure of
every eye. Night after night, through the winter evenings, it flashes in
the sky a little farther west; finally it gleams in the western sky at
sunset, jewels the rim of the horizon, and disappears.
[Figure 106: Orion and the "Dog Star."]
[Figure 107: THE WINTER BATTLE OF ORION, THE GIANT, AND TAURUS, THE BULL.
These beautiful constellations first make their appearance during
October, although they may be viewed to better advantage during the
winter-time, when they lie directly in the south.]