a zodiacal constellation. Aquarius is the Water-Bearer, and the water
jar which he carries is represented by a small, but distinct, Y of
stars from which flows a stream of faint stars toward the southeast
and south. Aquarius, like Capricornus, is a rather uninteresting
constellation, as it is made up of inconspicuous third- and
fourth-magnitude stars. The entire region covered by these two groups
of stars is remarkably barren, since it contains not a single first-
or even second-magnitude star and little to attract the observer's
eye.
To relieve the barrenness of this region, there appears just to the
south of Aquarius and southeast of Capricornus, sparkling low in the
southern sky on crisp October evenings, the beautiful first-magnitude
star Fomalhaut in the small southern constellation of Piscis
Australis, The Southern Fish. This star is the farthest south of
all the brilliant first-magnitude stars that can be seen from the
middle latitudes of the Northern Hemisphere. The constellation in
which it lies is so close to the southern horizon in our latitudes
that it cannot be seen to any advantage, and it is at best very
inconspicuous, containing no other objects of interest. Fomalhaut
cannot be mistaken for any other star visible at this time of year
in the evening, since it stands in such a solitary position far to
the south. At the time of which we are writing it will be found a few
degrees east of the meridian.
XII
NOVEMBER
Directly south of Cassiopeia and Cepheus, the circumpolar
constellations with which we became acquainted last month, and almost
overhead in our latitudes in the early evening hours of November, lie
Pegasus, The Winged Horse, and Andromeda, The Woman Chained.
According to the legend, Cepheus was king of Ethiopia, and Cassiopeia
was the beautiful, but vain, queen who dared to compare herself in
beauty with the sea-nymphs. This so enraged the nymphs that, as a
punishment for her presumption, they decided to send a terrible
sea-monster to ravage the coast of the kingdom. The king and queen,
upon consulting the oracle, found that the only way to avert this
calamity would be to chain their daughter Andromeda to the rocks and
permit the monster to devour her.
[Illustration: NOVEMBER--ANDROMEDA AND PEGASUS]
As the story goes, the valiant hero, Perseus, chanced to be riding
through the air on his winged horse and saw, far beneath him the
beautiful maiden chained to the rocks and the frightful monster
approaching to devour her. He immediately went to the rescue, and,
after a terrible struggle with the monster, succeeded in overpowering
him and thus saved the maiden from a dreadful fate. Perseus and the
fair Andromeda were married shortly afterward, and at the end of a
happy life the pair were transferred to the heavens. Cassiopeia, the
vain queen, was ordered to be bound to a chair and, with the king
Cepheus at her side, to be swung continually around the north pole of
the heavens that she might be taught a lesson in humility.
The constellation Cetus, representing the sea-monster, will be found
to the southeast and south of Pisces, The Fishes, which lie south of
Andromeda and Pegasus.
The Great Square in Pegasus is the most conspicuous configuration
of stars to be seen in the heavens in autumn evenings. The star
that marks the northeastern corner of The Great Square belongs to
the constellation of Andromeda and marks the head of the maiden,
who is resting upon the shoulders of Pegasus, The Winged Horse. The
three bright stars nearly in a straight line outline the maiden's
body, Alpha, or Alpheratz, as it is called, being the star in the
head, Beta or Mirach in the waist, and Gamma or Almach in the left
foot. The last-named star, which is farthest to the northeast in
the diagram, was, in the opinion of the noted astronomer Herschel,
the finest double star in the heavens. The two stars into which the
telescope splits it are of the beautifully contrasted shades of
orange and sea green.
A second most interesting object in Andromeda and one of the finest
in the entire heavens is The Great Andromeda Nebula, which is faintly
visible without the aid of a telescope as a hazy patch of light. It
is believed that in reality this nebula is a great universe composed
of many thousands of stars so distant that no telescope can show the
individual members and that the light from it takes many thousands
of years to span the abyss that separates it from the solar system.
Some magnificent photographs of The Great Andromeda Nebula have been
taken with powerful telescopes. It is through the use of photography
that the nebulæ can best be studied, for a photographic plate after
long exposure, reveals a wonderful detail in the structure of these
objects that the human eye fails to see. On a clear, dark evening
one may find The Great Andromeda Nebula by the aid of two faint stars
with which it makes a small triangle, as shown in the chart. This
nebula is the only one of the spiral nebula that can be seen in these
latitudes without the aid of a telescope, though there are several
spiral nebulæ in the southern heavens that can be thus seen.
Lying to the northwest of The Great Square in Pegasus are a number of
faint stars that outline the shoulders and head of the winged steed,
while the stars to the southwest of the square outline his forelegs.
The creature is represented without hind quarters in all star
atlases. The space within The Great Square contains no bright stars,
and as a result, the outline of the square stands out with great
distinctness. There are, in fact, no stars of the first magnitude in
either Pegasus or Andromeda, though there are a number of the second
and third magnitude which very clearly show the distinctive forms of
these two star-groups.
Pisces, The Fishes, the constellation just south of Andromeda and
Pegasus, is the first of the twelve zodiacal constellations. It
consists of the southern fish, lying in an east-to-west direction,
and the northern fish, lying nearly north and south, the two touching
at the southeastern extremity of the constellation.
[Illustration: NOVEMBER--PISCES]
There is in Pisces not a single bright star, and its only point of
interest is to be found in the fact that it contains the point,
marked by the cross and letter V in the diagram, that is known
variously as "the vernal equinox," "the equinoctial point" and "The
First Point in Aries." This is a very important point of reference
in the heavens, just as the meridian of Greenwich is for the earth,
and it marks the point where the sun crosses the equator going north
in the spring. Owing to the Precession of the Equinoxes, as it is
called, this point is gradually shifting its position westward
through the zodiacal constellations at a rate that will carry it
completely around the heavens through the twelve zodiacal groups in
a period of 25,800 years. Since the beginning of the Christian era,
this point has backed from the constellation of Aries, which lies
just east of Pisces, into Pisces, though it still retains its name of
"The First Point in Aries."
XIII
DECEMBER
The eastern half of the sky on early December evenings is adorned
with some of the finest star-groups in the heavens; but as we are
considering for each month only the constellations that lie on or
near the meridian in the early evening hours, we must turn our
eyes for the present from the sparkling brilliants in the east to
the stars in the less conspicuous groups of Aries, The Ram, and
Cetus, The Whale. We will also become acquainted this month with
the beautiful and interesting constellation of Perseus, the hero of
mythical fame to whom we referred last month in connection with the
legend of Cepheus and Cassiopeia. Cetus, you will recall, represents
the sea-monster sent to devour Andromeda, the daughter of Cepheus and
Cassiopeia. We have included the constellation of Andromeda in our
diagram for this month, since it is so closely associated in legend
with the constellations of Perseus and Cetus, though we also showed
it last month.
The brightest star in Perseus, known as Alpha Persei, is at the
center of a curved line of stars that is concave or hollow toward
the northeast. This line of stars is called the Segment of Perseus,
and it lies along the path of the Milky Way, which passes from this
point in a northwesterly direction into Cassiopeia. According to the
legend, Perseus, in his great haste to rescue the maiden from Cetus,
the monster, stirred up a great dust, which is represented by the
numberless faint stars in the Milky Way at this point. The star Alpha
is in the midst of one of the finest regions of the heavens for the
possessor of a good field-glass or small telescope.
A short distance to the southwest of Alpha is one of the most
interesting objects in the heavens. To the ancients, it represented
the baleful, winking demon-eye in the head of the snaky-locked
Gorgon, Medusa, whom Perseus vanquished in one of his earliest
exploits and whose head he carried in his hand at the time of the
rescue of Andromeda. To the astronomers, however, Algol is known
as Beta Persei, a star that has been found to consist of two stars
revolving about each other and separated by a distance not much
greater than their own diameters. One of the stars is so faint that
we speak of it as a dark star, though it does emit a faint light.
Once in every revolution the faint star passes directly between us
and the bright star and partly eclipses it, shutting off five-sixths
of its light. This happens with great regularity once in a little
less than three days. It is for this reason that Algol varies in
brightness in this period. There are a number of stars that vary in
brightness in a similar manner. Their periods of light-change are all
very short, and the astronomers call them eclipsing variables. At
its brightest, Algol is slightly brighter than the star nearest to
it in Andromeda, which is an excellent star with which to compare it.
[Illustration: DECEMBER--PERSEUS, ARIES AND CETUS]
Perseus is another one of the constellations lying in the Milky Way
in which temporary stars or novas have suddenly flashed forth. At the
point indicated by a cross in the diagram, Dr. Anderson, an amateur
astronomer of Scotland, found on February 21, 1901, a new star as
brilliant as the pole-star. On the following day it became brighter
than a star of the first magnitude. A day later it had lost a third
of its light, and in a few weeks it was invisible without the aid
of a telescope. In a year it was invisible in all except the most
powerful telescopes. With such telescopes, it may still be seen as a
very faint nebulous light.
Triangulum and Aries are two rather inconspicuous constellations that
lie on, or close to, the meridian at this time. There is nothing
remarkable about either of these groups, except that Aries is one of
the twelve zodiacal constellations. Some centuries ago, the sun was
to be found in Aries at the beginning of spring and the position it
occupies in the sky at that time was called the First Point in Aries.
As this point is slowly shifting westward, as we have explained
elsewhere, the sun is now to be found in Pisces, instead of Aries at
the beginning of spring and does not enter Aries until a month later.
Pisces was one of the constellations for November and we showed in
that constellation the present position of the sun at the beginning
of spring.
Two stars in Aries--Alpha and Beta--are fairly bright, Alpha being
fully as bright as the brightest star in Andromeda. Beta lies a short
distance to the southwest of Alpha, and a little to the southwest
of Beta is Gamma, the three stars forming a short curved line of
stars that distinguishes this constellation from other groups. The
remaining stars in Aries are all faint.
Just south of Aries lies the head of Cetus, The Whale. This is an
enormous constellation that extends far to the southwest, below
a part of Pisces, which runs in between Andromeda and Cetus. Its
brightest star, Beta, Diphda, or Deneb Kaitos, as it is severally
called, stands quite alone not far above the southwestern horizon.
It is almost due south of Alpha Andromedæ, the star in Andromeda
farthest to the west, which it exactly equals in brightness. The head
of Cetus is marked by a five-sided figure composed of stars that are
all faint with the single exception of Alpha, which is fairly bright,
though inferior to Beta or Diphda.
Cetus, though made up chiefly of faint stars, and on the whole
uninteresting, contains one of the most peculiar objects in the
heavens, the star known as Omicron Ceti or Mira (The Wonderful). This
star suddenly rises from invisibility nearly to the brightness of a
first-magnitude star for a short period once every eleven months.
Mira was the first known variable star. Its remarkable periodic
change in brightness was discovered by Fabricius in the year 1596, so
its peculiar behavior has been under observation for three hundred
and twenty-five years. It is called a long-period variable star,
because its variations of light take place in a period of months
instead of a few hours or days, as is the case with stars such as
Algol. Mira is not only a wonderful star, it is a mysterious star
as well, for the cause of its light-changes are not known, as in
the case of Algol where the loss of light is produced by a dark
star passing in front of a brighter star. Mira is a deep-red star,
as are all long-period variable stars that change irregularly in
brightness. It is visible without a telescope for only one month or
six weeks out of the eleven months. During the remainder of this
time, it sometimes loses so much of its light that it cannot be found
with telescopes of considerable size. Its periods of light-change are
quite variable as is also the amount of light it gains at different
appearances.
It is believed that the cause of the light-changes of Mira is to be
found within the star itself. It has been thought that dense clouds
of vapors may surround these comparatively cool, red stars and that
the imprisoned heat finally bursts through these vapors and we see
for a short time the glowing gases below; then the vapors once more
collect for a long period, to be followed by another sudden outburst
of heat and light.
It is interesting to remember in this connection that our own sun has
been found to be slightly variable in the amount of light and heat
that it gives forth at different times, and the cause of its changes
in light and heat are believed to lie within the sun itself.
XIV
STARS OF THE SOUTHERN HEMISPHERE
As one travels southward from the mid-latitudes of the northern
hemisphere into the tropics our familiar circumpolar constellations
sink lower and lower in the northern heavens and strange and
unfamiliar star-groups rise gradually above the southern horizon.
If we make our southward journey in the winter months the first of
the southern constellations to come fully into view is the small
star-group just south of Lepus known as Columba (The Dove), whose
brightest star Phact is of the second magnitude. A line drawn from
Procyon to Sirius and extended as far again brings us to this star
and a line from Betelgeuze to Sirius extended an equal distance
brings us to Zeta Argus which is equal to Phact in brightness. The
two lines intersecting at Sirius make the "Egyptian X" as it is
called.
Magnificent, blue-white Canopus, the most brilliant star in the
heavens next to Sirius, a veritable diamond sparkling low in the
southern sky, now commands our unqualified admiration. Canopus lies
about 35° south of Sirius and is invisible north of the 37th parallel
of latitude. At nine o'clock in the evening of February 6th it can be
seen just above the southern horizon in that latitude and is then a
conspicuous object in Georgia, Florida and the Gulf States.
"The star of Egypt whose proud light
Never hath beamed on those who rest
In the White Islands of the West."
writes Moore of Canopus in "Lalla Rookh."
Along the Nile Canopus was an object of worship as the god of waters.
At the time of their erection, 6400 B.C., a number of temples in
Upper Egypt were oriented so as to show Canopus at sunrise at the
autumnal equinox, and other temples erected many centuries later were
oriented in a similar manner. In China, as late as 100 B.C., and in
India also Canopus was an object of worship.
The astronomer tells us that Canopus is immeasurably distant from the
earth. It has been estimated to be forty thousand times more luminous
than our sun.
Canopus is located in the constellation of Argo Navis which is
the largest and most conspicuous constellation in the heavens.
In addition to Canopus it contains a number of second- and
third-magnitude stars and is subdivided for convenience into Puppis,
The Prow; Carina, The Keel; and Vela, The Sails. Huge as it is,
Argo Navis represents only half of a ship for the stern is lacking.
According to the legend this ship was built by Argos, aided by
Pallas Athene, for Jason, the leader of the expedition of the fifty
Argonauts who sailed from Greece to Colchis in search of the golden
fleece. Pallas Athene placed in the bow of the ship a piece of
timber from the speaking oak of Dodona to guide the crew and warn
them of dangers and after the voyage the ship was supposed to have
been placed in the heavens.
[Illustration: SOUTHERN CONSTELLATIONS--1. IN FEBRUARY]
In Argo Navis is one of the finest telescopic objects in the heavens,
the Keyhole Nebula, as it is usually called, from a peculiar-shaped
dark patch in its brightest part. On the border of this nebula is the
deep-red Wonder Star of the southern hemisphere, Eta Argus, which
varies suddenly and unexpectedly in brightness between the seventh
and first magnitudes. In 1843 it burst forth with a splendor rivaling
Sirius and maintained this brilliancy for nearly ten years and then
slowly waned in brilliancy until it disappeared to the unaided eye
in 1886. The surrounding nebula also seems to share in its peculiar
fluctuations of brightness. Eta Argus is now a star of the seventh
magnitude and since it is still varying fitfully in brightness it is
believed that the history of its light-changes is not complete.
Among the constellations of the southern heavens near the meridian
in February we see in addition to Argo Navis the constellations
of Dorado, The Goldfish; Hydrus, The Serpent, and Tucana, The
Toucan. Though insignificant in appearance Dorado contains what was
described by Sir John Herschel as one of the most extraordinary
objects in the heavens, a worthy rival of The Great Orion Nebula and
in some respects very similar to it, The Great Looped Nebula, "the
center of a great spiral." In Dorado also is located The Greater
Magellanic Cloud which looks like a detached portion of the Milky
Way though it is far removed from it. To the naked eye it resembles
a small white cloud about 4° in extent. In the telescope it bears a
close resemblance to a typical portion of the Milky Way. A similar
formation known as The Lesser Magellanic Cloud is located in Hydrus.
It has been estimated that the distance of The Lesser Cloud is 80,000
light-years and that it is receding from us.
In Tucana is located one of the finest globular star clusters in
the heavens, known as 47 Tucanæ. This cluster and Omega Centauri,
a globular star cluster in Centaurus, are the two nearest of all
the globular clusters. They are distant from the earth about 22,000
light-years and it is known that the combined light of the thousands
of stars of which each cluster is composed is about one million times
that of our own sun.
In the western sky in the southern hemisphere in February may be seen
the brilliant, white, first-magnitude star Achernar in the river
Eridanus, the long, winding constellation that, we recall, starts
near the brilliant Rigel in Orion and disappears from the view of
northern observers below the southern horizon, extending its course
far into the southern hemisphere. Achernar means "The End of the
River" and this is nearly its position in the constellation.
Though Argo Navis is the largest and most important constellation of
the southern hemisphere, Crux, The Southern Cross, far-famed in story
and legend as well as for its historical associations, is beyond a
doubt the most popular.
The best time to view the Southern Cross is in June or July when
it is near the meridian. It is not seen to advantage in the months
of January or February. It then lies on its side and close to the
horizon and therefore is dimmed by atmospheric haze so that it almost
invariably is a disappointing object to the tourist from the north
who usually views it for the first time in one of these months. The
Cross is viewed to advantage in the latitude of Rio or Valparaiso
and it is best seen from the Straits where it rides high overhead.
It is not seen to advantage from the latitudes of Cuba or Jamaica.
It is small, only 6° in extent from north to south and less in width
and it lies in the most brilliant portion of the Milky Way which is
here a narrow stream only three or four degrees wide. Directly below
the Cross is the noted Coal Sack, apparently a yawning chasm in the
midst of its brilliant surroundings though probably in reality a dark
nebula. Viewed with the telescopes a number of stars are to be seen
projected on this dark background.
The Southern Cross is to the inhabitants of the southern hemisphere
what the Big Dipper is to those who dwell in the northern
hemisphere--an infallible timepiece. The upright of the Cross points
toward the south pole of the heavens which lies in a region where
there is a singular dearth of bright stars, the nearest star to the
south pole being a faint fifth-magnitude star called Sigma Octantis.
When seen in the southeast or southwest the Cross lies on its side,
but when passing the meridian it stands nearly upright. Humboldt,
referring to this fact, says:
"How often have we heard our guides exclaim in the savannahs of
Venezuela and in the desert extending from Lima to Truxillo,
'Midnight is past, the Cross begins to bend.'"
By the explorers of the sixteenth century the Cross was taken as
a sign of heaven's approval of their attempt to establish the
Christian religion in the wilds of the New World. This thought is
beautifully expressed in Mrs. Hemans' lines in "The Cross of the
South."
"But to thee, as thy lode-stars resplendently burn
In their clear depths of blue, with devotion I turn
Bright Cross of the South! and beholding thee shine,
Scarce regret the loved land of the olive and vine.
Thou recallest the ages when first o'er the main
My fathers unfolded the ensign of Spain,
And planted their faith in the regions that see
Its imperishing symbol ever blazoned in thee."
Alpha Crucis, the brightest star in Crux, is at the foot of the
Cross. It consists in reality of two second-magnitude stars forming a
beautiful double while a third fifth-magnitude star one and one-half
minutes of arc distant makes with this pair a combination similar to
our Mizar and Alcor of the Big Dipper though the separation is not
great enough to be visible to the naked eye. The second-magnitude
star at the head of the Cross is a deep orange in color and the two
stars that mark the ends of the cross-arm are white third-magnitude
stars.
[Illustration: SOUTHERN CONSTELLATIONS--2. IN JULY]
One of the finest constellations of the southern hemisphere is
Centaurus, The Centaur, which surrounds Crux on the north and is more
than 60° in length. Its center lies about 50° south of Spica in Virgo
and below the tail of Hydra. Alpha Centauri, its brightest star and
the nearest star to the solar system, four and one-third light-years
away, is a golden-yellow double star that forms with the star Beta
Centauri on the west a configuration similar to that of Castor and
Pollux in Gemini, only one that is far more striking because of the
superior brilliancy of the stars. Alpha Centauri lies in the Milky
Way and transits the meridian at the same time with Arcturus though
it cannot be seen north of the 29th parallel. Alpha Centauri, like
Canopus, was an object of worship in Egypt and a number of temples in
northern Egypt were oriented to its emergence from the sun's rays in
the morning at the autumnal equinox, between 3000 and 2575 B.C.