Rensselaer Union, Volume 7, Number 16, Rensselaer, Jasper County, 7 January 1875 — SIRIUS, THE DOG-STAR. [ARTICLE]

SIRIUS, THE DOG-STAR.

“ One star differeth from another star in glory, ’’ and among tho six thousand stars visible to the unassisted eye in the celestial sphere, or the twenty million revealed there by telescopic research, the greatest glory surrounds the peerless orb known under the name of Sirius. It belongs to a little constellation, Canis Major, a cluster of thirty-one stars, possessing otherwise no noticeable feature, situated south and east of Orion, and universally known from the unrivaled luster of its leading brilliant. Sirius is a superb object in the winter sky, coming to the meridian on the 11th of February, and surpassing in size and lustrous light its nearest rivals, Betelguex and Procyon, with which it forms an equilat eral triangle, whose angular points of starry glory sparkle like diamonds of the first water. —— -. For the origin of the name of this glittering brilliant we must go Jiack to the early history of astronomy, among the people who dwelt m Egypt around the river Nile. The rise ana overflow of the famous river was to the ancient inhabitants at first a source of annoyance and distress, on account of the inundation of the land adjacent to its shores. The occurrence was considered as accidental until long observation had shown that it was an annual event, and then its cause was a source of still greater anxiety. The heavens above and the earth below were carefully studied for a solution of the mystery.’ At length patient study was rewarded; the problem was solved. A few days before the rivar began to rise a bright star rose above the morning horizon, just before the sun’s appearance. Every year the mysterious star appeared at the same season and in the same position, of at least so near it that the slight deviation was not recognized by the unpraCticed astronomers of the time. Every year its appearance was followed by the rising of the waters. Therefore those who dwelt near the river left their dwellings and sought temporary homes in more elevated localities, while they watched the overflow with mingled feelings of superstitious fear and bright hopes of agricultural prosperity. Thus the star was like a watch-dog, giving warning of the approach ot the enemy, and for this reason it received the name of Haaut, or Tayaut, signifying dog in their language. As the star was closely associated with the sacred river, it was honored with a second name, Sihor, one of the names of the Nile; or, according to other authority, Siris, the Egyptian word for the rising of the river. This is the derivation for our name for tl;e star, Sirius. To the Egyptians this star was the most important one in the heavens, for it marked the commencement of their agricultural year. The slightest varia tion in its color was carefully observed, and from its greater or lesser brilliancy, indicating in reality the condition of the atmosphere, they eagerly gathered omens of fruitful harvest or desolating famine. They paid to it divine honors on account of its influence in producing fertilizing inundations, and superstitiously believed that the conjunction of sun and star caused the excessive heat of the season. On account of the prevalence of malignant disease at this time they associated with it a malarious influence. This belief prevailed universally in ancient times, and the superstition still survives in the modern dog-days. The star had a peculiar god, called Typhpn, to whom a cruel sacrifice was red-haired victims, usually foreigners, who were annually seized for this purpose. The Greeks adopted the superstition and the Romans followed their lead, sacrificing yearly a brown dog to Sirius to render it propitious to their flocks and herds. The evil agency continued for forty days, twenty days before the heliacal rising of the star and twenty days after the event. These were the “Dies caniculares” of classic times* At that remote period they commenced on the 4th of August and lasted till the 14th of September. But the rising of Sirius varies with the latitude of the place, and in the same latitude is perceptibly changed after a course of years by the precession of the equinoxes. At the present time Sirius rises with the sun about the 12th-of August, and the classical Ag-days extend from the 24th of July to the Ist of September. As modern dog-days extend from the 3d of July to the 11th of August it will readily , that they have no reference to / the rising of Sirius. It was naturally supposed that Sirius, from its superior size, was nearer to us than any of its companions, but modem observation has established |he fact that

this is not the case. The stars that we call fixed are, in reality, moving onward through space in obedience to laws that are not yet fully comprehended. The movement, though apparently imperceptible, is, in reality, rapid beyond conception. The Milky-Way, to which our sun belongs, is revolving in a vast orbit around some undiscovered center, and the motion of our sun may be the cause of a portion of the measurable motion of a few of the stellar suns. Now, the stars having the greatest proper motion must be nearest to us, jus# as a man seems to walk faster at a little distance from us than when he is much farther off. In the great majority of stars not the slightest trace of movement can be delected by the most careful observation. As the earth sweeps on in her orbit round the sun she is, at opposite points of it, 188,000,000 miles nearer to some of the surrounding stars, and yet this enormous distance does not change the position of most of the stars a fraction of a hair’s breadth; therefore, the vast orbit of the earth is a mere point as seen from these distant orbs. But nine or ten stars have been found to give evidence of movement —proper motion, as it is called —and thus afford data on which their distances can be calculated. Alpha Centauris, a southern, first-magnitude star, has the most rapid motion, and is considered the nearest to us. But its motion is not quite one sec ond of a degree, and it is separated from us by the enormous distance of 224,000 times the earth’s distance from the sun, this being the unit for starry measurements. Therefore, for 20,000,000,000,000 miles a traveler beyond the boundaries of the “solar system, passing through space with the amazing velocity of light, 184,000 miles a second, would be three years and six months in reaching the nearest of the stars. Finite power utterly fails to comprehend the dimensions of a universe fashioned on so vast a scale! Sirius has also a proper motion, five times as slow as Alpha Centauris. It is 1,375,000 times the earth’s distance from the sun, which is 91,430,000 miles. It takes light twenty-two years to traverse this distance; so that if this star were to-day to be blotted from the sky it would continue to shine there with undiminished luster for twenty-two years. Not only has the distance of Sirius been determined but its size compared with our sun has been approximately puting the dimensions of a star is to measure its light. There are twenty stars of the first magnitude and nineteen are much farther from us than Alpha Centauris, although many of them are nearly as brilliant. Therefore we reason that they must exceed that star in size and mass. Now, Sirius must far surpass this sparkling gem of the southern sky, for it is four times as bright and five times as far away. Since it is five times as far away it should shine with one-twenty-fifth of the light, and, being apparently four times as bright, it is in reality 100 times as bright. As Alpha is three times as bright as the sun would be, removed to the same distance, Sirius must be 300 times as bright as the sun. If we assume that the intrinsic brightness of the star is the same as the intrinsic brightness of the sun, we shall have an immense sun fourteen times the diameter of our sun, with a volume exceeding his more than 2,000 times. This gives Sirius a diameter of more than 12,000,000 miles. Let us imagine a blazing sun stretching from the earth’s center, filling the intervening space between us and the moon, and extending more than 5,500,000 miles beyond, and we have some faint dawning of a conception of the incomprehensible dimensions of this immense globe of fire, the greatest aggregation of solar matter measurable thus far by terrestrial instruments! Great changes have taken place m the color of Sirius since it was first observed. In the early ages of astronomy it was of a fiery red, after which it gradually faded to a pure white, and it has now taken on a bluish or greenish tint. It holds a leading position in the class of white stars, which includes the highest conditions of development in the astral universe. Curious and unaccountable vagaries have always marked the movements of this star. It was found that it did not move in the heavens in a straight line and with the uniform velocity of the fixed stars, but varied its motion in such a way as to indicate powerful disturbing Influences in its vicinity. Here was a knotty problem that astronomers did not fail to attack, but no solution was reached until about half a century since. Bessel, a German observer, was convinced that the disturbance was caused by the attraction of an invisible satellite revolving around the shining orb. Other observers calculated the orbit of the attracting body, independently reaching the same result, and they even went so far as to indicate its position at certain times. At last no doubt remained as to the existence of the disturber, but it continued to elude the search of the best telescopes. In 1862 a telescope, with an object-glass of eighteen and a half inches in diameter, was completed by the famous opticians, Messrs? Alvan Clark & Sons. The new instrument was pointed to Sirius as a test of its power, and the long-looked-for companion came immediately into view, at the distance of ten seconds from the primary. The glad tidings went quickly round our little globe, and all the great telescopes were pointed to the bright star. When the exact position was known, the companion was easily detected by skillful observers. It took nearly four years to settle the question whether the observed satellite was really the disturbing body. It was. found that fits observed position and motion corresponded so nearly witlTthose predicted from theory that no doubt of the identity between the theoretical and visible satellite remained. Another modern discovery concerning Sirius relates to what is technically called star-drift. Certain stars appear to be drifting from us, others to be drifting toward us. On account of the brightness of Sirius Dr. Huggins selected it for a beautiful and delicate experiment to determine whether sUrs

have a proper motion in the direction of the line of sight from the earth. Astronomers can determine if a star moves up or down, to the right or a certain mean’ position, but they cannot determine if the star moves backward or forward. But Dr. Huggins solved the problem from a spectroscopic application of the laws of light. Light moves in waves. If the wave-length of a particular ray from a star varies in length from the normal wave-length of that ray, then the star is approaching or receding, according as the deviation varies. The spectroscopist has a delicate way of elucidating this law. The rainbow-tinted spectrum of this star is crossed by known dark lines. If one of these lines is changed toward the red end of the spectrum, the observer knows that the star is swiftly receding; if it changes toward the violet end, it is swiftly approaching. After a series of the most careful measurements, it was found that Sinus is receding at the rate of twenty-nine and a half miles a second. We cannot yet tell whether the earth is moving from the star or the star from the earth. Even with this incredible speed, the passage of a million years will make no perceptible difference in the appearance of the king star of our universe, and the lifetime of the present inhabitants of the globe is a period too insignificant to be thought of when dealing with this far-distant star! The question naturally arises: How can it be proved that the star is in reality a sun, made up of constituents like those of our sun, and giving forth heat and light under sjmilar conditions? The revelations of the spectroscope have satisfactorily settled this important-mat ter.Sirius gives a spectrum of great beauty, although its low altitude renders the observation of the finer lines very diflicult. Its spectrum is composed of rays of the seven colors, crossed by four dark and broad lines, ano by numerous fine ones. As its spectrum presents the same general appearance as the solar spectrum, it is proved that the star is incandescent, and that its light comes to us through certain vapors like those forming the sun’s photosphere. The four broad and dark lines indicate the presence of hydrogen, and some of the faint ones are due to sodium, magnesium and iron. Therefore Sirius is a real sun, constituted in the way, and containing elements identical with our sun. Thus we see that this resplendent star was an object of wonder and delight, as well as of superstitious fear, in the earliest ages of astronomical observation, and that the patient research and unwearied perseverance of modern observers have met with a brilliant reward in the marvelous discoveries that have followed their efforts. It exceeds a million times the distance of the sun from the earth, and is a gigantic globe, with a diameter of 12,000,000 miles and a volume more than 2,000 times greater than that of the sun. It gives out heat and light in a proportion to which that given out by our lesser luminary dwindles into nothingness. It is made up of constituents existing in all the bodies of the solar system, and it rules over at least one huge planet of proportions corresponding to its great principal. Tts color, changing from fiery red to blue-tinted white, gives evidence of vast commotion around its huge circumference. It is so far away that light, with its amazing velocity, takes twenty-two years to reach us from its far-distant confines; and yet so near that, while running away from us at the rate of twenty-nine and a half miles a second, we can see its light, feel its heat, measure its circumference, weigh its mass, define its substance and watch the movement of its dark satellite. And yet this glorious leader of the starry host is but one of twenty million visible to telescopic sight, many among the distant glimmerers doubtless its equal, or far exceeding its inconceivable mass. It is not given to finite power to comprehend the dimensions of a universe created on so grand a scale. But mortal imagination may seek to picture the glory of such a sun, the highest type of starry development, and fancy the planetary orbs revolving around the beaming center, manifesting the various and complicated conditions of physical existence .It may also picture some of them at least as fitted for the abode of intelligent beings of an order adapted to a position so exalted in the economy of the universe. We have occasionally, on this planet, glimpses of vastly higher orders of intelligence in the existence of a few individuals gifted far above their peers, whose fame will be borne from generation to generation as long as the world endures. Why should not the inhabitants of the worlds revolving around Sirius be as far above these exceptional-specimens of the human race as a Shakespeare, a Milton, or a Sir Isaac Newton is above the most untutored barbarian?—.®. M. Converse, in Appleton's Journal.