IVMARCH

February—Orion

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 wassix 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 interferometergive 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.Whenshining with its greatest brilliancy it is a brighter object than the nearbystarAldebaran, 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.

February—Auriga

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 beautifulfirst-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 appearto 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.

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 theIliadthis reference to Sirius:

"Terrific glory! for his burning breathTaints 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.

March—Canis Major

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 timeand is a most conspicuous configuration in the evening sky.

March—Gemini and Canis Minor

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 onthe 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 thetwin 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 inMaud—

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

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.

Near the meridian this month we find between Auriga and Ursa Major, and east of Gemini, the inconspicuous constellation of Lynx, which contains not a single bright star and is a modern constellation devisedsimply to fill the otherwise vacant space in circumpolar regions between Ursa Major and Auriga.

April—Cancer

Just south of the zenith at this time, and lying between Gemini and Leo, is Cancer, The Crab, the most inconspicuous of all the zodiacal constellations. There are no bright stars in this group, and there is also nothing distinctive about the grouping of its faint stars, though we can readily find it, from its position between the two neighboring constellations of Gemini and Leo by reference to the chart.

In the position indicated there we will see on clearevenings a faint, nebulous cloud of light, which is known as Praesepe, The Beehive, or as The Manger, the two faint stars flanking it on either side being called Aselli, The Asses. This faint cloud can be easily resolved by an opera-glass into a coarse cluster of stars that lie just beyond the range of the unaided human vision.

To the ancients, Praesepe served as an indicator of weather conditions, and Aratus, an ancient astronomer, wrote of this cluster:

"A murky manger, with both starsShining unaltered, is a sign of rain.If while the northern ass is dimmedBy vaporous shroud, he of the south gleam radiant,Expect a south wind; the vaporous shroud and radianceExchanging stars, harbinger Boreas."

This was not entirely a matter of superstition, as we might possibly imagine, for the dimness of the cluster is simply an indication that vapor is gathering and condensing in the atmosphere, just as a ring around the moon is an indication of the same gathering and condensation of vapor that precedes a storm.

Some centuries ago the sun reached its greatest distance north of the equator—which occurs each year at the beginning of summer—at the time when it was passing through the constellation of Cancer. Our tropic of Cancer, which marks the northern limit of the torrid zone, received its name from this fact. At the time when the sun reaches the point farthest north, its height above the horizon changes very little fromday to day, and for a short time it appears to be slowly crawling sideways through the heavens, as a crab walks, and for this reason, possibly, the constellation was called Cancer, The Crab. At the present time the "Precession of the Equinoxes," or westward shifting of the vernal equinox—the point where the sun crosses the equator going north in the spring—brings the sun, when it is farthest north, in Gemini instead of in Cancer. At the present time, then it would be more accurate to speak of the tropic of Gemini, though this in turn would be inaccurate aftera lapse of centuries, as the sun passed into another constellation at the beginning of summer. The tropic of Capricorn, which marks the farthest southern excursions of the sun in its yearly circuit of the heavens, should also more appropriately be called the tropic of Sagittarius, as the sun is now in Sagittarius instead of Capricornus at the time when it is farthest south, though the point is slowly shifting westward into Scorpio.

Mythology tells us that Cancer was sent by Juno to distract Hercules by pinching his toes while he was contending with the many-headed serpent in the Lernean swamp. Hercules, the legend says, crushed the crab with a single blow, and Juno by way of reward placed it in the heavens.

In Cancer, according to the belief of the Chaldeans, was located the "gate of men," by which souls descended into human bodies, while in Capricornus was the "gate of the gods," through which the freed souls of men returned to heaven.

April—Hydra

Hydra, the many-headed serpent with which Hercules contended, is represented by a constellation of great length. It extends from a point just south of Cancer, where a group of faint stars marks the heads, to the south and southeast in a long line of faint stars. It passes in its course just south of Crater and Corvus, the two small star-groups below Leo (see constellations for May), which are sometimes called its riders, and it also stretches below the entire length of the long, straggling constellation of Virgo. At thistime we can trace it only to the point where it disappears below the horizon in the southeast. It contains but one bright star, Alphard, or Cor Hydrae as it is also called, standing quite alone and almost due south at this time. Hydra, as well as Lynx and Cancer, contains no noteworthy or remarkable object and consists chiefly of faint stars. Alphard is, in fact, the only bright star that we have in the constellations for this month. It chances that these three inconspicuous star-groups, Lynx, Crater, and Hydra, lie nearest to the meridian at this time, separating the brilliant groups of winter from those of the summer months.

April—Lynx

Ursa Major, the Great Bear, and Ursa Minor, the Lesser Bear, or, as they are more familiarly called, the Big Dipper and the Little Dipper, are the best known of all the constellations visible in northern latitudes. They are called circumpolar constellations, which means "around the pole." For those who live north of 40° N. Lat. they never set, but can be seen at all hours of the night and at all times of the year. In fall and winter evenings Ursa Major lies below the pole and near the horizon, and so is usually hidden more or less from view by trees or buildings. It is during the early evening hours of late spring and summer that this constellation is seen to the best advantage high in the sky above the pole. If one looks due north at the time mentioned, it will be impossible to miss either of these constellations.

To complete the outline of the Great Bear, it is necessary to include faint stars to the east, which form the head of the Bear, and other faint stars to the south, which form the feet, but these are all inconspicuous and of little general interest.

The two stars in the bowl of the Big Dipper through which an arrow is drawn in the chart, arecalled the Pointers, because an imaginary line drawn through these two stars and continued a distance about equal to the length of the Big Dipper, brings us to the star Polaris, or the North Star, at the end of the handle of the Little Dipper, which is very close to the north pole of the heavens, the direction in which the earth's axis points. The pole lies on the line connecting the star at the bend in the handle of the Big Dipper with Polaris, and is only one degree distant from the pole-star.

May—Ursa Major and Ursa Minor

The distance between the Pointers is five degrees ofarc, and the distance from the more northerly of these two stars to Polaris is nearly thirty degrees. We may find it useful to remember this in estimating distances between objects in the heavens, which are always given in angular measure.

A small two and one-half inch telescope will separate Polaris into two stars eighteen seconds of arc apart. The companion star is a faint white star of the ninth magnitude.

Twenty years or so ago it was discovered with the aid of the spectroscope that the brighter of the two stars was also a double star, but the two stars were so close together that they could not be seen as separate stars in any telescope. Later it was found that the brighter star was in reality triple, that is, it consists of three suns close together. The faint white companion star formed with these three suns a system of four suns revolving about a common center of gravity. Still more recently it has been discovered that the brightest of these four suns varies regularly in brightness in a period of a little less than four days. It belongs to the important class of stars known as Cepheid variable stars, whose changes of light, it is believed, are produced by some periodic form of disturbance taking place within the stars themselves.

With one exception, Polaris is the nearest to the earth of all these Cepheid variable stars, which are in most instances at very great distances from the solar system. The latest measurements of the distance of Polaris show that its light takes about two centuriesto travel to the earth, or, in other words, that it is distant two hundred light-years.

Like all Cepheid variables, Polaris is a giant star. It gives forth about five hundred and twenty-five times as much light as our own sun. If Polaris and the sun were placed side by side at a distance of thirty-three light-years, the sun would appear as a star of the fifth magnitude, just well within the range of visibility of the human eye, while Polaris would outshine Sirius, the brightest star in the heavens.

As a practical aid to navigators, Polaris is unsurpassedin importance by any star of the northern hemisphere of the heavens. At the equator the pole-star lies in the horizon; at the north pole of the earth it is in the zenith or directly overhead. Its altitude or height above the horizon is always equal to the latitude of the place of observation. As we travel northward from the equator toward the pole we see Polaris rise higher and higher in the sky. In New York the elevation of Polaris above the horizon is forty degrees, which is the latitude of the city.

The Pointers indicate the direction of Polaris and the true north, while the height of Polaris above the horizon tells us our latitude. These kindly stars direct us by night when we are uncertain of our bearings, whether we travel by land or sea or air. They are the friends and aids of explorers, navigators and aviators, who often turn to them for guidance.

Bryant writes thus beautifully of Polaris in hisHymn to the North Star:

Constellations come and climb the heavens, and go.Star of the Pole! and thou dost see them set.Alone in thy cold skies,Thou keep'st thy old unmoving station yet,Nor join'st the dances of that glittering train,Nor dipp'st thy virgin orb in the blue western main.On thy unaltering blazeThe half wrecked mariner, his compass lost,Fixes his steady gaze,And steers, undoubting, to the friendly coast;And they who stray in perilous wastes by night,Are glad when thou dost shine to guide their footsteps right.

On thy unaltering blazeThe half wrecked mariner, his compass lost,Fixes his steady gaze,And steers, undoubting, to the friendly coast;And they who stray in perilous wastes by night,Are glad when thou dost shine to guide their footsteps right.

The star at the bend in the handle of the Big Dipper, called Mizar, is of special interest. If one has good eyesight, he will see close to it a faint star. This is Alcor, which is Arabic for The Test. The two stars are also called the Horse and the Rider.

Mizar forms with Alcor what is known as a wide double star. It is, in fact, the widest of all double stars. Many stars in the heavens that appear single to us are separated by the telescope into double or triple or multiple stars. They consist of two or more suns revolving about a common center, known as their center of gravity. Sometimes the suns are so close together that even the most powerful telescope will not separate them. Then a most wonderful little instrument, called the spectroscope, steps in and analyzes the light of the stars and shows which are double and which are single. A star shown to be double by the spectroscope, but not by the telescope, is called a spectroscopic binary star.

Mizar is of historic interest, as being the first double star to be detected with the aid of the telescope. A very small telescope will split Mizar up into two stars. The brighter of the two is a spectroscopic binary star beside, so that it really consists of two suns instead of one, with the distance between the two so small that even the telescope cannot separate them. About this system of three suns which we know as the star Mizar, the faint star Alcor revolves at a distance equal to sixteen thousand times the distance of the earth from the sun.

May—Leo

If we follow the imaginary line drawn through the Pointers in asoutherlydirection about forty-five degrees, we come to Leo, The Lion, one of the zodiacal constellations. There should be no difficulty in finding the constellation Leo, as its peculiar sickle-shaped group of bright stars makes it distinctive from all other constellations. At the time we have mentioned, that is, the early evening hours, it will lie a little to the southwest of the zenith. Leo is one of the finest constellations and is always associated with the spring months because it is then high in the sky in the evening.Regulus is the beautiful white star which marks the handle of The Sickle, and the heart of Leo; and Denebola is the second-magnitude star in the tail of Leo.

May—Corvus and Crater

Due south of Denebola, about thirty degrees, we find the small star-group known as Crater, The Cup, which is composed of rather faint and inconspicuous stars. Just east of Crater is the group known as Corvus, The Crow, which forms a very characteristic little four-sided figure of stars differing very little from one another in brightness. These two star groups lie far to the south in our latitudes; but if we lived twenty degrees south of the equator, we would find them nearly overhead, at this time of the year. Just south of Corvus and Crater we find Hydra, one of the constellations for April which extends beneath these constellations and also beneath Virgo, one of the June constellations.

The star-groups that occupy the center of the celestial stage in mid-latitudes of the northern hemisphere during the early evening hours of June are Boötes, often called The Hunter, (although the word means Herdsman or Shouter), which will be found overhead at this time; Virgo, The Maiden, largest of the zodiacal constellations, lying nearly due south; Canes Venatici, The Hunting Dogs; Corona Borealis, The Northern Crown, and Coma Berenices.

The gorgeous orange-hued Arcturus in Boötes and the beautiful bluish-white Spica in Virgo, like a diamond in its sparkling radiance, form with Denebola in Leo, which we identified in May, a huge equal-sided triangle that is always associated with the spring and early summer months.

To the west of Boötes, below the handle of the Big Dipper, is a region where there are few conspicuous stars. Here will be found Canes Venatici (The Hunting Dogs with which Boötes is supposed to be pursuing the Great Bear around the north pole), and, further south, Coma Berenices (Bernice's Hair).

The brighter of the two Hunting Dogs, which is also the brightest star in the entire region covered by these two constellations, appears as a beautiful blue-and-yellowdouble star in the telescope. It was named Cor Caroli (Heart of Charles) by the astronomer Halley in honor of Charles II of England, at the suggestion of the court physician, who imagined it shone more brightly than usual the night before the return of Charles to London. Of more interest to astronomers is the magnificent spiral nebula in this constellation, known as the "Whirlpool Nebula," appearing as a faint, luminous patch in the sky, of which many photographs have been taken with the great telescopes. This entire region, from Canes Venatici to Virgo, abounds in faint spiral nebulæ that for some reason not yet understood by astronomers are crowded together in this part of the heavens where stars are comparatively few. It is believed that there are between five hundred thousand and a million of these spiral nebulæ in the entire heavens, and the problem of their nature and origin and distance is one that the astronomers are very anxious to solve. Many wonderful facts are now being learned concerning these faint nebulous wisps of light which, with a few exceptions, are observable only with great telescopes. They reveal their spiral structure more clearly to the photographic plate than to the human eye, and some magnificent photographs of them have been taken with powerful telescopes.

Coma Berenices, south of Canes Venatici and southwest of Boötes, is a constellation that consists of a great number of stars closely crowded together, and just barely visible to the unaided eye. As a result, it has the appearance of filmy threads of light, whichdoubtless suggested its name to the imaginative ancients, who loved to fill the heavens with fanciful creations associated with their myths and legends. These stars form a moving cluster of stars estimated to be at a distance of about 270 light-years from the solar systems.

June—Boötes, Canes Venatici and Coma Berenicis

This region, so lacking in interesting objects for the naked-eye observer, is a mine of riches to the fortunate possessors of telescopes; and the great telescopes of the world are frequently pointed in this direction, exploring the mysteries of space that abound here.

Just to the east of Boötes is the exquisite little circlet of stars known as Corona Borealis, the Northern Crown. It consists of six stars arranged in a nearly perfect semicircle, and one will have no difficulty in recognizing it. Its brightest star, Alpha, known also by the name of Alphacca, is a star of the second magnitude.

Boötes is one of the largest and finest of the northern constellations. It can be easily distinguished by its peculiar kite-shaped grouping of stars or by the conspicuous pentagon (five-sided figure) of stars which it contains. The most southerly star in this pentagon is known as Epsilon Boötes and is one of the finest double stars in the heavens. The two stars of which it consists are respectively orange and greenish-blue in color.

By far the finest object in Boötes, however, is the magnificent Arcturus, which is the brightest star in the northern hemisphere of the heavens. This star will be conspicuous in the evening hours throughout the summer months, as will also the less brilliant Spica in Virgo.

Some recent measurements show that Arcturus is one of our nearer neighbors among the stars. Its distance is now estimated to be about twenty-one light-years. That is, a ray of light from this star takes twenty-one years to reach the earth, traveling at the rate of one hundred and eighty-six thousand miles per second. It would seem as if we should hardly speak of Arcturus, twenty-one light-years away, as a near neighbor, yet there are millions of stars that are far moredistant from the earth, and very few that are nearer to us than Arcturus.

The brightness of Arcturus is estimated to be about forty times that of the sun. That is, if the two bodies were side by side, Arcturus would give forth forty times as much light and heat as the sun.

Arcturus is also one of the most rapidly moving stars in the heavens. In the past sixteen centuries it has traveled so far as to have changed its position among the other stars by as much as the apparent width of the moon. Most of the stars, in spite of their motionsthrough the heavens in various directions, appear today in the same relative positions in which they were several thousand years ago. It is for this reason that the constellations of the Egyptians and of the Greeks and Romans are the same constellations that we see in the heavens today. Were all the stars as rapidly moving as Arcturus, the distinctive forms of the constellations would be preserved for only a very few centuries.

June—Virgo

Virgo, which lies south and southwest of Boötes, is a large, straggling constellation, consisting of a Y-shaped configuration of rather inconspicuous stars. It lies in the path of our sun, moon and planets, and so is one of the zodiacal constellations. The cross in the diagram indicates the present position of the autumnal equinox, the point where the sun crosses the equator going south, and the position the sun now occupies at the beginning of fall.

Spica, the brightest star in Virgo, is a bluish-white, first-magnitude star, standing very much alone in the sky. In fact, the Arabs referred to this star as "The Solitary One." Its distance from the earth is not known, but must be very great as it cannot be found by the usual methods. The spectroscope shows that it consists of two suns very close together, revolving about a common center in a period of only four days.

Within the branches of the "Y" in Virgo, and just to the north of it, is the wonderful nebulous region of this constellation, but it takes a powerful telescope to show the faint spiral nebulæ that exist here in greatprofusion. All of these spirals are receding from the plane of the Milky Way with enormous velocities. The spiral nebulæ are, in fact, the most rapidly moving objects in the heavens.

Due east of the little circlet of stars known as Corona Borealis, and almost directly overhead in our latitude (40° N.) about nine o'clock in the evening in the early part of July, is the large constellation of Hercules, named for the famous hero of Grecian mythology. There are no stars of great brilliancy in this group, but it contains a large number of fairly bright stars arranged in the form outlined in the chart. The hero is standing with his head, marked by the star Alpha Herculis, toward the south, and his foot resting on the head of Draco, The Dragon, a far-northern constellation with which we become acquainted in August.

July—Hercules

Alpha Herculis, the best known star in this constellation, is of unusual interest. Not only is it a most beautiful double star, the brighter of the two stars of which it is composed being orange, and the fainter greenish-blue, but it is also a star that changes in brightness irregularly. Both the orange and the blue star share in this change of brightness. There are a number of stars in the heavens that vary in brightness, some in very regular periods, and others, like Alpha Herculis, irregularly. These latter stars arenearly always deep orange or reddish in color. One may note this variation in the brightness of Alpha Herculis by comparing it from time to time with some nearby star that does not vary in brightness.

The Great Hercules Cluster—A Universe of SunsTaken with 60-inch Reflector of the Mt. Wilson Observatory

The Great Hercules Cluster—A Universe of Suns

Taken with 60-inch Reflector of the Mt. Wilson Observatory

The constellation of Hercules is a very rich field for the possessor of even a small telescope. Here are to be found beautifully colored double stars in profusion, and, in addition, two remarkable clusters of stars. The brighter of the two is known as the Great Hercules Cluster. Its position is shown on the chart, and, under favorable conditions—that is, on a clear,dark night, when there is no moonlight—it may be seen without the aid of a telescope as a small, faint patch of light. One would never suspect from such a view what a wonderful object this cluster becomes when seen with the aid of a powerful telescope. Photographs taken with the great telescopes show this faint wisp of light as a magnificent assemblage of thousands of stars, each a sun many times more brilliant than our own sun. The crowded appearance of the stars in the cluster is due partly to the fact that it is very distant from the earth, though neighboring stars in the cluster are indeed much nearer to one another than are the stars in the vicinity of our solar system. It has been found that this cluster is so far away that its light takes over thirty-six thousand years to reach the earth. At the distance of this cluster, a sun equal in brightness to our own sun would be so faint that the most powerful telescope in the world would not show it. So we know that the stars that are visible in the Hercules cluster are far more brilliant than our sun. A fair-sized telescope will show about four thousand stars in this cluster, but the greatest telescopes show over one hundred thousand in it, and there are without doubt many more too faint to be seen at all. The Hercules cluster is called a globular star-cluster, because the stars in it are arranged nearly in the form of a sphere. There are in the heavens about ninety such clusters whose distances have been found, and they are among the most distant of all objects. Most of them are very faint, and a few are over two hundredthousand light-years distant from the earth. The Hercules cluster is one of the nearest and is the most noted of all of these globular clusters. It is considered to be one of the finest objects in the heavens. The other cluster in Hercules is also very fine, but not to be compared with this one.

July—Ophiuchus and Serpens

Just to the south of Hercules are two constellations, Ophiuchus, The Serpent-Bearer, and Serpens, The Serpent, which are so intermingled that it is difficult to distinguish them. There are in these two constellations, as in Hercules, no stars of unusual brilliancy, but alarge number of fairly bright stars. The brightest star in Ophiuchus is known as Alpha Ophiuchi and it marks the head of the Serpent-Bearer. The two stars, Alpha Ophiuchi and Alpha Herculis, are close together, being separated by a distance about equal to that between the Pointers of the Big Dipper. Alpha Ophiuchi is the brighter of the two, and it is farther east.

Ophiuchus, according to one legend, was once a physician on earth, and was so successful as a healer that he could raise the dead. Pluto, the god of the lower world, became alarmed for fear his kingdom would become depopulated, and persuaded Jupiter to remove Ophiuchus to a heavenly abode, where he would be less troublesome. The serpent is supposed to be a symbol of his healing powers. The head of Serpens is marked by a group of faint stars just south of Corona Borealis and southwest of Hercules. From here a line of fairly bright stars marks the course of Serpens southward to the hand of Ophiuchus. Two stars close together and nearly equal in brightness mark the hand with which the hero grasps the body of the serpent. The other hand is marked by an equally bright single star some distance to the eastward where the two constellations again meet. Ophiuchus is thus represented as holding the serpent with both hands. It is not an easy matter to make out the outlines of these straggling groups, but there are in them several pairs of stars nearly equal in brightness and about as evenly spaced as the two stars in the one hand of Ophiuchus,and these, as well as the diagram, will be of aid in tracing the two groups.

Just south of Serpens and Ophiuchus lies one of the most beautiful and easily recognized constellations in the heavens. This is the constellation of Scorpio, The Scorpion, which will be found not far above the southern horizon at this time. The small constellation of Libra, The Scales, which lies just to the northwest of Scorpio, was at one time a part of this constellation and represented the creature's claws, but some centuries ago its name was changed to Libra. Both Scorpio and Libra are numbered among the twelve zodiacal constellations—that is, they lie along the ecliptic, or apparent yearly path of the sun among the stars. Scorpio is the most brilliant and interesting of all the zodiacal groups. The heart of the Scorpion is marked by the magnificent first-magnitude star Antares, which is of a deep reddish color. The name signifies Rival of Ares (Mars). It is so called because it is the one star in the heavens that most closely resembles Mars, and it might be mistaken for the ruddy planet if one were not familiar with the constellations. At times, when Mars is at a considerable distance from the earth, it is almost equal in brightness and general appearance to this glowing red star in the heart of the Scorpion. In its trips around the sun, Mars passes occasionally very close to Antares, and the two then present a very striking appearance.

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