Part 2

All stars of first, second and third magnitude are given in the diagrams without exceptions as such stars are visible to everyone on clear nights.

The constellations given in the following pages include practically all of the constellations that can be seen in 40° N. Latitude. A diagram is given for each constellation.

In this latitude it is impossible to see the constellations of the southern hemisphere that lie within 40° of the south pole of the heavens. A brief chapter with diagram treats of these constellations that are invisible in mid-latitudes of the northern hemisphere.

II

JANUARY

One of the most easily recognized constellations in the heavens is Taurus, The Bull, a zodiacal group which lies just south of the zenith in our latitudes in the early evening hours about the first of January.

Taurus is distinguished by the V-shaped group of The Hyades, which contains the bright, red, first-magnitude star Aldebaran, representing the fiery eye of the bull. It also contains the famous cluster of faint stars known as The Pleiades, lying a short distance northwest of The Hyades.

No group of stars is more universally known than The Pleiades. All tribes and nations of the world, from the remotest days of recorded history up to the present time, have sung the praises of The Pleiades. They were "The Many Little Ones" of the Babylonians, "The Seven Sisters" of the Greeks, "The Seven Brothers" of the American Indians, "The Hen and Chickens" of many nations of Europe, "The Little Eyes" of the South Sea Islanders. They were honored in the religious ceremonies of the Aztecs, and the savage tribes of Australia danced in their honor. Many early tribes of men began their year with November, the Pleiad month; and on November 17th, when The Pleiades crossed the meridian at midnight, it was said that no petition was ever presented in vain to the kings of ancient Persia.

Poets of all ages have felt the charm of The Pleiades. Tennyson gives the following beautiful description of The Pleiades in _Locksley Hall_:

"Many a night I saw the Pleiades, rising through the mellow shade, Glitter like a swarm of fireflies tangled in a silver braid."

A well-known astronomer, not so many years ago, also felt the mysterious charm of The Pleiades and seriously expressed the belief that Alcyone, the brightest star of The Pleiades, was a central sun about which all other suns were moving. But we know that there is no foundation whatever for such a belief.

A fairly good eye, when the night is clear and dark, will make out six stars in this group arranged in the form of a small dipper. A seventh star lies close to the star at the end of the handle and is more difficult to find. It is called Pleione, and is referred to in many legends as the lost Pleiad. Persons gifted with exceptionally fine eyesight have made out as many as eleven stars in the group; and with the aid of an ordinary opera-glass, anyone can see fully one hundred stars in this cluster. Astronomers have found that The Pleiades cluster contains at least two hundred and fifty stars, all drifting slowly in the same general direction through space, and that the entire group is enveloped in a fiery, nebulous mist which is most dense around the brightest stars. It is not known whether the stars are being formed from the nebula or whether the nebula is being puffed off from the stars. The brightest star, Alcyone, is at least two hundred times more brilliant than our own sun, and all of the brighter stars in the group surpass the sun many times in brightness. It is believed that this cluster is so large that light takes many years to cross from one end of it to the other, and that it is so far from the earth that its light takes over three centuries to reach us, traveling at the rate of 186,000 miles a second.

The Hyades is a group of stars scarcely less famous than The Pleiades, and the stars in the group also form a moving cluster of enormous extent at a distance of 140 light-years from the earth.

Among the ancients, The Hyades were called the rain-stars, and the word Hyades is supposed to come from the Greek word for rain. Among the many superstitions of the past was the belief that the rising or setting of a group of stars with the sun had some special influence over human affairs. Since The Hyades set just after the sun in the showery springtime and just before sunrise in the stormy days of late fall, they were always associated with rain. In Tennyson's _Ulysses_ we read:

"Through scudding drifts the rainy Hyades Vex'd the dim sea."

The Hyades outline the forehead of Taurus, while two bright stars some distance to the northeast of the V form the tips of the horns. Only the head and forequarters of the bull are shown in the star-atlases that give the mythological groups, for, according to one legend, he is swimming through the sea and the rest of his body is submerged. According to another legend, Taurus is charging down upon Orion, The Warrior, represented by the magnificent constellation just to the southeast of Taurus, of which we shall have more to say next month.

Aldebaran is the Arabic word for "The Hindmost," and the star is so called because it follows The Pleiades across the sky. It is one of the most beautiful of all the many brilliant stars visible at this time and we might profit by following the advice of Mrs. Sigourney in _The Stars_:

"Go forth at night And talk with Aldebaran, where he flames In the cold forehead of the wintry sky."

Next to Aldebaran in the V is the interesting double star Theta, which we can see as two distinct stars without a telescope.

Directly south of Taurus is Eridanus, sometimes called Fluvius Eridanus, or The River Eridanus. Starting a little to the southeast of Taurus, close to the brilliant blue-white star Rigel in Orion, it runs to the westward for a considerable distance in a long curving line of rather faint stars, bends sharply southward for a short distance, then curves backward toward the east once more, and, after running for some distance, makes another sharp curve to the southwest and disappears below the southern horizon. Its course is continued far into the southern hemisphere. Its brightest star, Achernar, is a star of the first magnitude, but it lies below the horizon in our latitudes.

Eridanus contains no star of particular interest to us. Most of the numerous stars that mark its course are of the fourth and fifth magnitude. It contains but two stars of the third magnitude, one at the beginning of its course and one close to the southwestern horizon. The beautiful constellation of Perseus lies just to the north of Taurus and should rightfully be considered among the constellations lying nearest to the meridian in January, but we give this constellation among the star groups for December because of its close association with the nearby constellations Andromeda and Pegasus in legend and story.

III

FEBRUARY

Across the meridian, due south, between eight and nine o'clock in the evening in the early part of February, lies Orion, The Warrior, generally considered to be the finest constellation in the heavens. Orion is directly overhead at the equator, and so is seen to advantage from all parts of the world except the extreme northern and southern polar regions.

A group of three faint stars outlines the head of Orion. His right shoulder is marked by the deep-red, first-magnitude star Betelgeuze (meaning armpit), and his left shoulder by the bright white star Bellatrix, The Amazon. Orion stands facing Taurus, The Bull, and brandishes in his right hand a club, outlined by a number of faint stars extending from Betelgeuze toward the northeast. The top of the club lies near the tips of the horns of Taurus. In his left hand he holds up a lion's skin, which we can trace in another curving line of faint stars to the west and northwest of Bellatrix. The brilliant, blue-white, first-magnitude star Rigel lies in the left foot, and the second-magnitude star Saiph, a little to the east of Rigel, is in the right knee. Three evenly spaced stars lying in a straight line that is exactly three degrees in length form the Belt of Orion, and from the Belt hangs the Sword of Orion, outlined by three faint stars. The central star in the Sword appears somewhat blurred and is the multiple star Theta, in the midst of the great Orion nebula, the finest object of its kind in the heavens. Entangled in the meshes of this glowing nebula are a number of brilliant suns, appearing to us as faint stars because of their great distance. The star Theta, in the heart of the nebula, is seen with a powerful telescope to consist of six stars; that is, it is a sextuple star. Even with a small telescope, four of these stars can readily be seen, arranged in the form of a small trapezium. The lowest star in the Sword is a triple star, and the entire constellation abounds in double, triple, and multiple stars.

From the central portion of the nebula extend many branches and streamers of nebulous light, and it is known that the entire constellation of Orion is enwrapped in the folds of this nebulosity, which forms a glowing, whirling mass of fiery gases in rapid rotation. This constellation is remarkable for the fact that all of its brighter stars, with the exception of the deep-red Betelgeuze, form one enormous, connected group of stars. They are all more or less associated with the great nebula and its branches, and are all extremely hot, white or bluish-white stars, known as helium stars, because the gas helium is so conspicuous in their atmospheres. The Orion stars are the hottest and brightest of all the stars.

Blazing Rigel, Bellatrix, and Saiph, marking three corners of the great quadrilateral, of which Betelgeuze marks the fourth corner, are all brilliant helium stars. So are the three stars in the Belt and the fainter stars in the Sword and the great nebula.

It has been estimated that the great Orion group of stars is over six hundred light-years from the earth, or about forty million times more distant than the sun. For more than six centuries the rays of light that now enter our eyes from these stars have been traveling through space with the speed of lightning. So we see Orion not as it exists today, but as it was six centuries ago. The extent of the Orion group of stars is also inconceivably great. Even the central part of the great nebula, which appears to our unaided eyes only as a somewhat fuzzy star, would extend from here to the nearest star and beyond, while our entire solar system would be the merest speck in its midst.

Betelgeuze, the red star that marks the right shoulder of Orion, is, as we have said, not a member of the Orion group. It has been estimated that it is about two hundred light-years from the earth, or only about one-third as far away as the other stars of the constellation.

Betelgeuze very recently has attracted universal attention, and will probably be considered an object of historic interest in the future, because it is the first star to have its diameter measured with the new Michelson interferometer, which is now being used so successfully to measure the diameters of the largest stars. The truly sensational discovery has been made that Betelgeuze is a supergiant of the universe, with a diameter of about 275,000,000 miles. Our own sun, which is known as a "dwarf" star, has a diameter of 864,000 miles. That is, Betelgeuze would make about thirty million suns the size of our own. If placed at the center of the solar system, it would fill all of the space within the orbit of Mars; and the planets Mercury, Venus, and the Earth would lie far beneath its surface. Measurements of the diameters of other giant stars which are now being made with the interferometer give results quite as startling as have been obtained in the case of Betelgeuze; and it has been found that several of these stars may even exceed Betelgeuze in size. Such a star is Antares, the fiery-red star in the heart of Scorpio, which is such a conspicuous object in the summer evening skies. All these huge stars are deep red in color, and some of them vary irregularly in brightness. Betelgeuze is one of the stars that changes in brightness in a peculiar manner from time to time. When shining with its greatest brilliancy it is a brighter object than the nearby star Aldebaran, in Taurus; but a few months or a year later it may lose so much of its light as to be decidedly inferior to Aldebaran. We may note for ourselves this remarkable change in the brightness of Betelgeuze by comparing the two stars from time to time.

Directly south of Orion lies the small constellation of Lepus, The Hare, which is made up of third-magnitude and fourth-magnitude stars. The four brighter stars are arranged in the form of a small, but distinct, quadrilateral, or four-sided figure, which may be easily seen in our latitudes. The small constellation of Columba, The Dove, which lies just south of Lepus, is so close to the horizon that it can not be seen to advantage in the mid-latitudes of the northern hemisphere. Neither Lepus nor Columba contain any object of unusual interest.

Due north of Orion, and lying in the zenith at this time, is Auriga, The Charioteer, represented, strange to say, with Capella, a goat, in his arms. The beautiful first-magnitude star Capella, golden-yellow in color, serves us in identifying the constellation. Close at hand are The Kids, represented by a group of three faint stars. Capella is one of the most brilliant stars of the northern hemisphere. It is almost exactly equal in brightness to Arcturus and Vega, stars conspicuous in the summer months, and it is a shade brighter than magnificent blue-white Rigel in Orion. Capella is about fifty light-years distant from the earth and is fully two hundred times more brilliant than our own sun. At the distance of Capella, the sun would appear to be considerably fainter than any one of the three stars in the nearby group of The Kids.

Capella is attended by a companion star so close to its brilliant ruler that it can not be seen as a separate star save with the aid of the most powerful telescopes. Its distance from Capella has been very accurately measured, however, by means of the interferometer, which is giving us the measurements of the diameters of the giant stars. It is known that this companion sun is closer to Capella than our planet earth is to the sun.

At no time of the year shall we find near the meridian so many brilliant and beautiful stars as appear in the month of February at this time in the evening. In addition to Capella, which is one of the three most brilliant stars in the northern hemisphere of the heavens, we have, in Orion alone, two stars of the first magnitude, Betelgeuze and Rigel, and five stars of the second magnitude, Bellatrix and Saiph and the three stars in the Belt. In addition, we have not far distant in the western sky, fiery Aldebaran in Taurus, and close on the heel of Orion in the east, Sirius, the brightest star in the heavens, in the constellation of Canis Major, The Greater Dog, as well as the first-magnitude star Procyon in Canis Minor, The Lesser Dog. Of these two groups we shall have more to say under the constellations for March.

IV

MARCH

To the southeast of Orion and almost due south at eight o'clock in the evening on the first of March lies the constellation of Canis Major, The Greater Dog, containing Sirius, the Dog-star, which far surpasses all other stars in the heavens in brilliancy.

Sirius lies almost in line with the three stars that form the Belt of Orion. We shall not have the slightest difficulty in recognizing it, owing to its surpassing brilliancy as well as to the fact that it follows so closely upon the heels of Orion.

Sirius is the Greek for "scorching" or "sparkling," and the ancients attributed the scorching heat of summer to the fact that Sirius then rose with the sun. The torrid days of midsummer they called the "dog-days" for this reason, and we have retained the expression to the present time. Since Sirius was always associated with the discomforts of the torrid season, it did not have an enviable reputation among the Greeks. We find in Pope's translation of the _Iliad_ this reference to Sirius:

"Terrific glory! for his burning breath Taints the red air with fever, plagues, and death."

In Egypt, however, many temples were dedicated to the worship of Sirius, for the reason that some five thousand years ago it rose with the sun at the time of the summer solstice, which marks the beginning of summer, and heralded the approaching inundation of the Nile, which was an occasion for great rejoicing among the Egyptians. It was, therefore, called the Nile Star and regarded by them with the greatest reverence.

Sirius is an intensely white hydrogen star; but owing to its great brilliancy and to the fact that it does not attain a great height above the horizon in our latitudes, its rays are greatly refracted or broken up by the atmosphere, which is most dense near the horizon, and as a result, it twinkles or scintillates more noticeably than other stars and flashes the spectrum colors--chiefly red and green--like a true "diamond in the sky"--a magnificent object in the telescope.

Sirius is one of our nearest neighbors among the stars. Only two stars are known to be nearer to the solar system. Yet its light takes about eight and a half years to flash with lightning speed across the great intervening chasm. It is attended also by a very faint star that is so lost in the rays of its brilliant companion that it can only be found with the aid of a powerful telescope. The two stars are separated by a distance of 1,800,000,000 miles; that is they are about as far apart as Neptune and the sun. They swing slowly and majestically about a common center, called their center of gravity, in a period of about forty-nine years. So faint is the companion of Sirius that it is estimated that twenty thousand such stars would be needed to give forth as much light as Sirius. The two stars together, Sirius and its companion, give forth twenty-six times as much light as our own sun. They weigh only about three times as much, however. The companion of Sirius, in spite of its extreme faintness, weighs fully half as much as the brilliant star.

There are a number of bright stars in the constellation of Canis Major. A fairly bright star a little to the west of Sirius marks the uplifted paw of the dog, and to the southeast, in the tail and hind quarters, are several conspicuous stars of the second magnitude.

A little to the east and much farther to the north, we find Canis Minor, The Lesser Dog, containing the beautiful first-magnitude star Procyon, "Precursor of the Dog"--that is, of Sirius. Since Procyon is so much farther north than Sirius and very little to the east, we see its brilliant rays in the eastern sky some time before Sirius appears above the southeastern horizon, hence its name. Long after Sirius has disappeared from view beneath the western horizon in the late spring, Procyon may still be seen low in the western sky. Procyon, also is one of our nearer neighbors among the stars, being only about ten light-years distant from the solar system. Like Sirius, it is a double star with a much fainter companion, that by its attraction sways the motion of Procyon to such an extent that we should know of its existence, even if it were not visible, by the disturbances it produces in the motion of Procyon. The period of revolution of Procyon and its companion about a common center is about forty years, and the two stars combined weigh about a third more than our own sun and give forth six times as much light. Canis Minor contains only one other bright star, Beta, a short distance to the northwest of Procyon. Originally, the name Procyon was given to the entire constellation, but it was later used only with reference to the one star. Procyon, Sirius, and Betelgeuze in Orion form a huge equal-sided triangle that lies across the meridian at this time and is a most conspicuous configuration in the evening sky.

Directly south of the zenith we find Gemini, The Twins, one of the zodiacal constellations. It is in Gemini that the sun is to be found at the beginning of summer. The two bright stars Castor and Pollux mark the heads of the twins, and the two stars in the opposite corners of the four-sided figure shown in the chart mark their feet.

Castor and Pollux, according to the legend, were the twin brothers of Helen of Troy who went on the Argonautic expedition. When a storm overtook the vessel on its return voyage, Orpheus invoked the aid of Apollo, who caused two stars to shine above the heads of the twins, and the storm immediately ceased. It was for this reason that Castor and Pollux became the special deities of seamen, and it was customary to place their effigies upon the prows of vessels. The "By Jimini!" of today is but a corruption of the "By Gemini!" heard so frequently among the sailors of the ancient world.

The astronomical name for Castor, the fainter star, is Alpha Geminorum, meaning Alpha of Gemini. As it was customary to call the brightest star in a constellation by the first letter in the Greek alphabet, it is believed that Castor has decreased considerably in brightness since the days of the ancients, for it is now decidedly inferior to Pollux in brightness, which is called Beta Geminorum. Of the two stars, Castor is the more interesting because it is a double star that is readily separated into two stars with the aid of a small telescope. The two principal stars are known to be, in turn, extremely close double stars revolving almost in contact in periods of a few days. Where we see but one star with the unaided eye, there is, then a system of four suns, the two close pairs revolving slowly about a common center of gravity in a period of several centuries and at a great distance apart.

The star Pollux, which we can easily distinguish by its superior brightness, is the more southerly of the twin stars and lies due north of Procyon and about as far from Procyon as Procyon is from Sirius.

The appearance of Gemini on the meridian in the early evening and of the huge triangle, with its corners marked by the brilliants, Procyon, Sirius, and Betelgeuze, due south, with "Great Orion sloping slowly to the west," is as truly a sign of approaching spring as the gradual lengthening of the days, the appearance of crocuses and daffodils, and the first robin. It is only a few weeks later--as pictured by Tennyson in _Maud_--

"When the face of the night is fair on the dewy downs, And the shining daffodil dies, and the Charioteer And starry Gemini hang like glorious crowns Over Orion's grave low down in the west."

V

APRIL

In the early evening hours of April the western sky is still adorned with the brilliant jewels with which we became familiar on the clear frosty evenings of winter. Orion is now sinking fast to his rest beneath the western horizon. Beautiful, golden Capella in Auriga glows in the northwest. Sirius sparkles and scintillates, a magnificent diamond of the sky, just above the southwestern horizon, while Procyon in Canis Minor, The Lesser Dog, and Castor and Pollux, The Twins, in the constellation of Gemini, are still high in the western part of the heavens.

In the northeast and east may be seen the constellations that will be close to the meridian at this time next month. Ursa Major, The Greater Bear, with its familiar Big Dipper, is now in a favorable position for observation. The Sickle in Leo is high in the eastern sky, and Spica, the brilliant white diamond of the evening skies of spring, is low in the southeast in Virgo.