also a spectroscopic binary with a period of only four days. It was the
first binary of this class to be discovered. In 1889 Pickering found
that its spectral lines were doubled every two days, from which he
inferred the duplicate character of the star and calculated the period
of revolution of its components.
Farther east we see Gemini, the “Twins.” It is a very beautiful
constellation, independently of the brightness of its leaders, Castor
and Pollux, or Alpha (α) and Beta (β). The feet of the imaginary twins
are dipped in the Milky Way nearly above the uplifted club of the giant
Orion, and close to the summer solstice. The successive belts of stars
crossing the figures of the Twins present an attractive appearance.
Castor, although the literal leader of the constellation, is not now
as bright as its neighbor, Pollux. A change of brightness must have
taken place. Castor is a celebrated binary with a period of about one
thousand years. The distance between the two stars composing it is
about 5″.5, and, both being bright, they can be separated with small
telescopes.
Pollux is very near the standard first magnitude in brightness. It has
a slightly orange tint in contrast with the whiteness of Castor. Like
Orion, Taurus, and Auriga, Gemini offers splendid fields of stars for
the opera-glass. A cluster, M35, not far above the place of the summer
solstice, is an object of rare beauty when seen with a low telescopic
power.
South of Gemini shines the bright star Procyon in Canis Minor, the
Lesser Dog. This star, whose name implies the “Preceder, or Announcer,
of the Dog,” because it rises a little ahead of Sirius, is the only
bright star of its constellation. It is interesting for having a dusky
companion whose existence was detected by the effects of its attraction
before any telescope had revealed it. With this companion Procyon forms
a binary system with a period of revolution of about forty years. The
star Beta (β) is named Gomeisa, from an Arabic word meaning the “Dim
One.” Procyon, Sirius, and Betelgeuse form a magnificent triangle,
through which flows the Milky Way.
We now return to the western part of the sky, where we see, beyond
Eridanus, the vast expanse covered by the constellation Cetus, the
“Whale.” The head lies on and over the equator above the western bend
of Eridanus. It is marked by a striking group of stars, of which Alpha
(α), or Menkar, the “Nose,” is the chief. The star Gamma (γ) is a fine
double; colors yellow and blue; distance 2″.5. Below and toward the
west will be found Omicron (ο), better known by its popular title of
Mira, the “Wonderful.” In some respects this is the most extraordinary
of all variable stars. It excited great astonishment when its
variations were first recorded in the seventeenth century. Most of the
time it is entirely invisible to the naked eye; but once in about ten
months it begins to brighten, and in a few weeks becomes conspicuous,
sometimes equalling the second magnitude in brightness. Then it
fades again, and in about three months disappears from naked-eye
vision, although it is never lost to the telescope, which follows it
down to the ninth magnitude, at which it remains, glowing redly, for
several successive months. Its variations are more or less irregular
both in period and in brightness. The causes are only conjectural.
About all that we can say is that here is a sun which once every ten
months blazes up to a thousand or fifteen hundred times its ordinary
brilliancy. The imagination can work its will with such a star as that.
The western part of Cetus is marked by a striking group of stars shaped
something like the bowl of an upturned dipper and by a lone, bright
star still farther west, Beta (β), or Deneb Kaitos, the “Tail of the
Whale.”
Above Cetus runs the long line of stars composing the constellation
Pisces, now the leader of the zodiac, since it contains the Vernal
Equinox. Alpha (α), or Al Rischa, the “Cord,” because it marks the
ribbon imagined to bind two fishes together by their tails, is directly
under the stars marking the head of Aries, to which we have already
referred. It is a double of very singular colors--green and blue. The
distance is about 3″.6. From Al Rischa the stars of the constellation
stream northward to the figure of the Northern Fish, whose nose touches
Andromeda, and westward to the Western Fish, which is situated under
the Great Square of Pegasus. The extraordinary tendency of the stars of
Pisces to run in streaming lines has been spoken of in Chapter III.
The other stars and constellations now visible are already familiar to
us. But we turn again for a moment to Polaris, which, being practically
fixed in the sky, can be seen at any season. I have referred to the
fact that this star for a long series of centuries has been a universal
guide to all the inhabitants of the northern hemisphere. In that
character its history is no less romantic than practically important.
One of the deepest impressions of my childhood was produced by an
acquaintance with a remarkable man who at that time seemed to me to be
a most wonderful traveller, since he had seen the Gulf of Mexico, the
Everglades of Florida, the Dismal Swamp of Virginia, and, according to
his story (which no boy would doubt), had battled with alligators and
tasted the delights of vagabond life on the great cotton plantations
of the South. I think he was the first who ever pointed out the North
Star to me, and he fired my imagination by tales of its connection
with the escape of negro slaves--escapes in which he professed to have
played a part. Many long winter evenings he sat by my father’s fireside
and fascinated his hearers with narratives of his adventures. But
nothing interested me more than what he said of the slaves following
the lead of the North Star, through the darkness of tangled swamps,
among deadly moccasins and lurking alligators, always fixing their eyes
upon “the star,” falling on their knees to it as their only friend and
guide. Trembling at the bay of pursuing bloodhounds, they would lie in
concealment during the daylight hours, and as soon as night came on
would look for their celestial sentinel, and follow unquestioningly its
indication of the way to freedom. However apocryphal these stories may
have been, they certainly had a basis of truth, and the impressions
then produced upon my mind concerning the character of Polaris as the
sure friend of those who are lost and in trouble have remained undimmed
in my memory. What a triumph will be that of the man who first visits
the north pole by night, and sees that star gleaming directly over his
head, while all the constellations solemnly circle about it, unresting
and unsetting!
FOOTNOTES:
[2] It should be said that throughout this book I am indebted for
many of the translations of star names to Richard Hinckley Allen’s
_Star Names and Their Meanings_, the most complete work of its kind in
existence.
V
THE PLANETS
The beginner will often be troubled in his observations by the presence
in some constellation of a brilliant object which outshines all of the
stars shown in his charts, and is plainly an interloper among them. He
may at once set the stranger down for one of the planets--it may be
Jupiter, Saturn, Mars, or Venus, or possibly, if close to the horizon,
Mercury. Uranus and Neptune will not disturb his equanimity, for the
latter is never, and the former seldom, visible to the naked eye.
Practice will quickly enable him to distinguish a planet from the true
stars, both by its greater apparent size and by the quality of its
light. The planets do not twinkle as do the stars. This arises from the
fact that they present measurable disks which reflect the sunlight,
but do not shine with a light of their own. No star shows a real disk,
even when viewed with a powerful telescope. The stars are mere points,
and the larger and better the telescope the smaller they appear. This
is not to say that they do not look brighter in a telescope, for the
larger stars are dazzling when viewed with a glass of large aperture;
but they are so distant that the mightiest of telescopes cannot reveal
their real surfaces in the form of disks. The apparent disks which they
present are due entirely to irradiation, and the higher the power the
smaller these spurious disks appear.
Another way in which the beginner may identify a planet is by observing
its motion. No planet remains long in the same position with regard
to neighboring stars. They all travel, at varying rates, from west to
east through the sky. But this motion is not constant, and at times it
is reversed. In the cases of Mars, Jupiter, and Saturn the reversal is
due to the fact that when they are in opposition to the sun the earth,
being nearer the sun than they are, outfoots them in eastward motion,
so that they appear for a time to move backward on their orbits. It
is like a fast train passing a slow one on a parallel track; to an
observer on the fast train the slow one seems to be either standing
still or moving backward. But Mercury and Venus, being nearer the sun
than the earth is, have at times a backward motion which is real.
Let us consider them only when they appear as “evening stars.” From
“superior conjunction” (_i. e._, the point occupied by the planet when
it is on the opposite side of the sun from the earth) to “greatest
eastern elongation” (greatest apparent distance from the sun in the
evening sky) both Mercury and Venus move eastward among the stars; from
“greatest eastern elongation” to “inferior conjunction” (_i. e._, the
point occupied by the planet when it is between the earth and the sun)
they move westward among the stars, or, in other words, approach the
sun.
The motions of Mercury and Venus are comparatively swift, particularly
that of the former. Few persons have ever seen Mercury, because of
its nearness to the sun. When well seen it is brighter than any
first-magnitude star. As an “evening star” it appears in the west
immediately after sunset about once every four months (more precisely
once every 116 days). It remains within view about twenty days, but
can be easily distinguished only for a week or so when it is nearest
eastern elongation. Every almanac gives the dates of its appearances.
Venus, being farther from the sun, travels less rapidly. It reappears
in the evening sky once in every 584 days, gradually withdrawing
from the sun, and growing brighter until it reaches greatest eastern
elongation, which may be as much as forty-seven degrees from the
sun, after which it approaches the sun, still becoming brighter for
several weeks, until at last it is lost in the glare of the sunlight.
During its excursions in the evening sky (and the same is true of its
morning apparitions), Venus becomes the most brilliant object in the
starry heavens, so brilliant, in fact, that many persons can hardly be
persuaded that it is not an artificial light, or some extraordinary
phenomenon in space. In the telescope it shows (as does Mercury,
also) phases like those of the moon, and when it is seen in the form
of a narrow crescent it becomes one of the most charming objects
imaginable. For more details about Mercury, Venus, and the other
planets, the reader may consult _Astronomy with the Naked Eye_.
Mars, Jupiter, and Saturn are more likely to cause confusion to the
beginner by getting “mixed up” with the stars of the constellations
he is studying, because they travel all round the sky, and may appear
in turn in each of the zodiacal constellations at any hour of the
night. The zodiacal constellations are twelve in number--Aries, Taurus,
Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricornus,
Aquarius, and Pisces--and they lie in succession along the course of
the ecliptic.
Mars is not remarkably brilliant except when it is in opposition to the
sun, which happens once every 780 days; but some of the oppositions
are much more important than the average, because they occur when Mars
is relatively near the earth. This planet is always distinguishable by
its ruddy color. In case it is mistaken for a star, the error can be
corrected by watching it for a few successive nights, when its motion
will become clearly apparent. On the average it moves eastward about
half a degree per day.
Jupiter, always very conspicuous when in view, outshines even Sirius,
though lacking the scintillation characteristic of that great star.
Its light has a slightly yellowish tint, and is remarkably steady.
Since it requires nearly twelve years to make a revolution round the
sky, Jupiter’s motion is not immediately apparent. It remains for a
long time in any constellation in which it may be found, travelling
eastward, on the average, about 5′ of arc, or one-sixth of the apparent
diameter of the moon, per day. In a month it moves about two and a half
degrees.
Saturn is yet more deliberate in its movements. Requiring almost thirty
years for a revolution, it may remain more than two years in the same
constellation, and its real motion will only become evident upon
careful observation continued for several weeks.
The best way to recognize the planets with certainty is to look up
their positions with the aid of the _American Ephemeris and Nautical
Almanac_, published annually by the Government at Washington. There
the right ascensions and declinations of all the planets are given for
any time of the year. Having these, you may find on the large-scale
charts the approximate place of the planet sought, and, if you choose,
indicate its position with a pencil-mark.
The study of the planets, even without telescopic aid, has a charm
hardly less potent than that of the stars. Mercury is fascinating
because of the difficulty of seeing him in the light of twilight or
dawn. The ancients were greatly puzzled by his dodges, and some of them
thought that he was a double personality, and gave him two names, one
for his morning and the other for his evening apparitions. With the
Egyptians he was respectively Set and Horus, and with the Greeks Apollo
and Hermes. The same was true of Venus, who was Phosphorus in the
morning and Hesperus in the evening.
Venus, after she passes the half-moon phase, becomes so bright that she
simply overpowers all stars in her neighborhood. Her splendor seems
almost supernatural, and she has frequently been seen at high noon, a
point of intense light burning in the blue sky.
Jupiter’s entrance into any constellation immediately alters its
familiar aspect, and he becomes its unquestioned leader, and remains
such until his slow eastward motion carries him on to reign in another
quarter of the firmament. He is never more impressive than when, in
consequence of the annual revolution of the heavens, he rises late some
night and takes the lingering star-gazer by surprise. Then all the
stellar hosts that for hours have held the watcher spellbound cease
their incantation in the presence of this great counter-charmer, to
whose power they, too, seem to bow. Although Venus at her brightest
outshines Jupiter, she lacks a certain majesty which he alone
possesses. His light is calm, steady, insistent, commanding. He does
not look like a star, but rather a _superstar_. If he beams at all, it
is not the hurried scintillation of the twinkling multitude around him.
Rising through a moisture-laden and wind-swept sky, where the stars are
like pulsating atoms, shaken apart and scattered in tinsel showers of
rainbow sparks, he glows unflickering, recognizing the aerial tumult
only by a deepening of color which makes him the more imposing. As
he mounts the heights of the sky he gleams ever brighter and ever
steadier, and, casting off the tarnish of the horizon, his supereminent
light glows with a splendor that is amazing. If you have an eye that
can detect one or two of Jupiter’s moons hiding close in his rays, you
may boast of your powers of vision, for that feat has been accomplished
by very few human beings. Humboldt heard of a German “master tailor”
who could do it. There are a few other cases on record. Most persons
cannot see them even with the aid of a strong opera-glass. There is a
superstition that they can be seen with a looking-glass, but it is only
ghostly reflections that are thus perceived--perhaps as real as any
other ghosts.
Saturn, although as bright as a first-magnitude star, is somewhat
disappointing as a naked-eye object, owing to the relative dulness
of its light. Like Jupiter, it shines with great steadiness, and a
practised eye could not mistake it for a fixed star. But its appearance
without a telescope gives no hint of the unearthly beauty with which
it astonishes the beholder when its rings are rendered visible. Not to
have seen those rings at least once in a lifetime, as they appear in a
powerful telescope, is to have missed one of the supreme spectacles of
creation.
Mars is never very brilliant except during favorable oppositions, when,
approaching within less than 40,000,000 miles of the earth, it hangs in
the midnight sky, gleaming red like a portent of disaster. The aspect
of Mars at such times is truly alarming. It is surprising to see what a
quantity of stained sunlight a world only about four thousand miles in
diameter is able to reflect across so vast a gap of space. The reason
why the ancients connected Mars with the god of war is plain enough
when he puts on his color.
Close conjunctions of the bright planets are exceedingly interesting
phenomena. Mars and Jupiter seen together when the former is near one
of its favorable oppositions make a scene of strange beauty. After long
intervals of time several of these great planets sometimes assemble
in the same quarter, and such conjunctions are always memorable
occurrences. The stars are forgotten in the presence of this new
constellation, and yet the tiniest of the sparks that seems to hide its
light in the depths beyond would master these great planets and make
gravitational slaves of them, as the sun does.
The planets are so conspicuous to our eyes, because of their relative
nearness, that it is not easy for the beginner in such studies to
realize how insignificant they actually are. But suppose that one
could fly like a spirit away from the earth and the neighborhood of
the sun, out into the deeps of interstellar space. As he moved away
the planets would seem to be swallowed up, one after the other, in the
solar rays. First Mercury would disappear, as if it had fallen into the
sun. It would be just like two neighboring lights which appear to draw
together and blend into one as the observer travels away from them, the
greater swallowing the less. Then brilliant Venus would go, plunging
into the great solar furnace, to be seen no more. Next the earth would
follow in the perspective holocaust. Mars would seem to draw nearer
until he, too, disappeared; Jupiter would follow; then Saturn; then
Uranus, and finally Neptune. When the last planet was gone the sun
would be seen shining alone, unattended, as if he had never had any
planets. Thus it may be with the stars; most of them may have systems
of planets circling round them, but at our distance these planets are
concealed in the rays of their primaries.
One would not need to go so far away as the stars in order to see
the sun apparently swallow his planets, as Saturn was fabled to have
swallowed his children. But as one approached the stellar region, the
sun itself would become a mere star. Fainter and fainter it appears,
glimmering and twinkling, deprived of its dominance, stripped of its
splendor, a pitiful spark now instead of an all-ruling and blinding
maker of daylight, until at last the far voyager from the earth,
gazing with his soul in his eyes, straining his vision to the utmost
to hold that glinting point clear of its fellows, _for it is his sun_,
suddenly, as a momentary film blurs his sight, loses it, and henceforth
seek as he may among the countless hosts that spangle the firmament,
he will never again find the day-star under whose cheery beams he
was born! Hidden in the Milky Way, one would have no more chance of
recognizing the sun than of finding a particular grain of sand on the
sea-shore. Man physical is as insignificant as the rock he dwells on
and as the eye-searing orb that lights him at his daily work; but man
spiritual is as great as the universe--and greater!
APPENDIX
URANOGRAPHY OR HEAVENLY DESCRIPTION OF THE CHURCHMEN
Many readers may be interested in seeing a list of the names given to
the constellations when, as mentioned in the Introduction, the starry
sky was “Christianized.” In the seventeenth century Julius Schillerius
put forth his _Cœlum Stellatum Christianum_, and Jacobus Bartschius a
celestial globe, in which all of the well-known constellations received
new and strictly orthodox names. Unfortunately the sponsors for these
names did not always agree in their choice, and a certain Harsdorfius
(who may have been the poet Philip Harsdoerfer, born at Nuremberg in
1607) added to the confusion by further varying the selection. Wilhelm
Schickard also introduced variations. In the following list the first
of the “Christian” names given is that chosen by Schillerius, while
their variants are due to either Harsdorfius, Schickard, or Bartschius:
ARIES--St. Peter--Abraham’s Ram.
TAURUS--St. Andrew--The Burnt Sacrifice.
GEMINI--St. James the Elder--Jacob and Esau.
CANCER--St. John the Evangelist.
LEO--St. Thomas--The Lion of Judah. (Observe that the variants are
generally more imaginative.)
VIRGO--St. James the Younger--The Virgin Mary.
LIBRA--St. Philip--Belshazzar’s Balances.
SCORPIO--St. Bartholomew.
SAGITTARIUS--St. Matthew--Ishmael.
CAPRICORNUS--St. Simon.
AQUARIUS--St. Jude--Naaman.
PISCES--St. Mathias--The Gospel Fishes.
URSA MINOR--St. Michael--One of Elisha’s Bears--The Wagon of Joseph.
URSA MAJOR--St. Peter’s Fishing-boat--Elisha’s other Bear--The Chariot
of Elias.
DRACO--The Innocents--The Dragon Infernal. (Quite a difference of
opinion.)
BOÖTES--St. Sylvester--Nimrod.
COMA BERENICES--The Scourge of Christ--Absalom’s Hair--Samson’s Hair.
CORONA BOREALIS--The Crown of Thorns--Queen Esther’s Crown.
HERCULES--The Three Wise Men of the East--Samson.
LYRA--The Saviour’s Manger--David’s Harp.
CYGNUS--The Cross of Calvary.
CASSIOPEIA--St. Mary Magdalen--Bathsheba.
CEPHEUS--St. Stephen--Solomon. (Solomon seems a better choice.)
PERSEUS WITH MEDUSA’S HEAD--David with the Head of Goliath--St. Paul.
ANDROMEDA--The Holy Sepulchre--Abigail. (The last reverses Andromeda’s
romance with a vengeance.)
AURIGA--Jacob--St. Jerome.
OPHIUCHUS ET SERPENS--St. Benedict--St. Paul and the Viper. (The
latter very pat.)
SAGITTA--The Lance of Calvary--Jonathan’s Arrow.
AQUILA--St. Katharine--The Standard of Rome.
DELPHINUS--The Canaanitish Woman’s Pitcher--Leviathan.
EQUULEUS--The Mystic Rose.
PEGASUS--St. Gabriel--Jeremiah’s King of Babylon.
TRIANGULUM--St. Peter’s Mitre--Emblem of the Trinity.
CETUS--Sts. Joachim and Anna--Jonah’s Whale.
ERIDANUS--The Red Sea with Moses Crossing It--The Brook of Cedron.
ORION--St. Joseph--Joshua. (The last a good choice.)
LEPUS--Gideon’s Fleece.
CANIS MAJOR--Tobias’s Dog--St. David.
CANIS MINOR--The Paschal Lamb.
ARGO NAVIS--Noah’s Ark. (Inevitable!)
HYDRA--The River Jordan.
CRATER (together with Corvus)--The Ark of the Covenant.
CORVUS (according to Schickard)--Elias’s Crow.
CENTAURUS--Abraham and Isaac.
LUPUS--Jacob.
ARA--The Altar of Incense.
CORONA AUSTRALIS--David’s Crown--Solomon’s Crown.
PISCIS AUSTRINUS--The Widow’s Meal Barrel--St. Peter’s Fish with Money
in Its Mouth.
GRUS }--Aaron.
PHŒNIX }
INDUS }--Job.
PAVO }
APUS }
CHAMELEON }--Eve.
PISCIS VOLANS }
TRIANGULUM AUSTRALE--The Cross of Christ. (At that time the Southern
Cross seems not to have been known.)
DORADO }
TOUCAN }--St. Raphael.
HYDRUS }
The southern constellations, Grus, Phœnix, Indus, Pavo, Apus,
Chameleon, Piscis Volans, Triangulum Australe, Dorado, Toucan, and
Hydrus, were all named by Bayer at the beginning of the seventeenth
century, so that the revisers were not upsetting any antique legends in
giving them more sacred names.
LETTERS OF THE GREEK ALPHABET EMPLOYED IN URANOGRAPHY