mercredi 1 octobre 2008

Canis Major 10

for the Egyptians always attributed to the Dog-star the beneficial influence of the inundation that began at the summer solstice; indeed, some have said that the Aethiopian Nile took from Sirius its name Siris, although others consider the reverse to be the case. Minsheu, who dwells much on this, ends thus: "Some thinke that the Dog-starre is called Sirius, because at the time the Dogge-starre reigneth, Nilus also overfloweth as though the water were led by that Starre." Indeed, it has been fancifully asserted that its canine title originated in Egypt, "because of its supposed watchful care over the interests of the husbandman; its rising giving him notice of the approaching overflow of the Nile."
Caesius cited for it Solechin as from that country, signifying the Starry Dog, and derived from the Egypto-Greek word Σολεκήν.
Perhaps it is the ancient importance of this Dog on the Nile that has given the popular name, the Egyptian X, to the figure formed by the stars Procyon and Betelgeuze, Naos and Phaet, with Sirius at the vertices of the two triangles and the centre of the letter. On our maps Sirius marks the nose of the Dog.
The Phoenicians are said to have known it as Hannabeah, the Barker.
The astronomers of China do not seem to have made as much of Sirius as did those of other countries, but it is occasionally mentioned, with other stars in Canis Major, as Lang Hoo; and Reeves quoted for it Tseen Lang, the Heavenly Wolf. Their astrologers said that when unusually bright it portended attacks from thieves.
Some have called it the Mazzārōth of the Book of Job; others the Ḣaṣīl of the Hebrews; but this people also knew it as Sihor, its Egyptian name, and Ideler thinks that the adoration of the Sɛērīm, or "Devils" of the Authorized Version of our Bible, the "He Goats" of the Revision, which, as we see in Leviticus xvii.7, was specially prohibited to the Jews, may have had reference to Sirius and Procyon, the Two Sirii or Shiʽrayān, that must have been well known to them in the land of their long bondage as worshiped by their taskmasters.
The culmination of this star at midnight was celebrated in the great temple of Ceres at Eleusis, probably at the initiation of the Eleusinian mysteries; and the Ceans of the Cyclades predicted from its appearance at its heliacal rising whether the ensuing year would be healthy or the reverse. In Arabia, too, it was an object of veneration, especially by the tribe of Kais, and probably by that of Kodhā'a, although Muḥammad expressly forbade this star-worship on the part of his followers. Yet he himself gave much honor to some "star" in the heavens that may have been this.
In early astrology and poetry there is no end to the evil influences that were attributed to Sirius.
Homer wrote, in Lord Derby's translation,
The brightest he, but sign to mortal man
Of evil augury.
Pope's very liberal version of the same lines,—
Terrific glory! for his burning breath
Taints the red air with fevers, plagues and death,—
seems to have been taken from the Shepheard's Kalendar for July:
The rampant Lyon hunts he fast with dogge of noysome breath
Whose baleful barking brings in hast pyne, plagues and dreerye death.
Spenser, however, was equally a borrower, for we find in the Aeneid:
p126 The dogstar, that burning constellation, when he brings drought and diseases on sickly mortals, rises and saddens the sky with inauspicious light;
and in the 4th Georgic:
Jam rapidus torrens sitientes Sirius Indos
Ardebat coelo,
rendered by Owen Meredith in his Paraphrase on Vergil's Bees of Aristaeus:
Swift Sirius, scorching thirsty Ind,
Was hot in heaven.
Hesiod advised his country neighbors, "When Sirius parches head and knees, and the body is dried up by reason of heat, then sit in the shade and drink," — advice universally followed, even till now, although with but little thought of Sirius. Hippocrates made much, in his Epidemics and Aphorisms, of this star's power over the weather, and the consequent physical effect upon mankind, some of his theories being current in Italy even during the last century; while the result of all physic depended upon the sign of the zodiac in which the sun chanced to be. Manilius wrote of Sirius:
from his nature flow
The most afflicting powers that rule below.
But these expressions as to the hateful character of the Dog-star may have been induced in part from the evil reputation of the dog in the East.
Its heliacal rising, 400 years before our era, corresponded with the sun's entrance into the constellation Leo, that marked the hottest time of the year, and this observation, originally from Egypt, taken on trust by the Romans, who were not proficient observers, and without consideration as to its correctness for their age and country, gave rise to their dies caniculariae, the dog days, and the association of the celestial Dog and Lion with the heat of midsummer. The time and duration of these days, although not generally agreed upon in ancient times, any more than in modern, were commonly considered as beginning on the 3d of July and ending on the 11th of August, for such were the time and period of the unhealthy season of Italy, and all attributed to Sirius. The Greeks, however, generally assigned fifty days to the influence of the Dog-star. Yet even then some took a more correct view of the matter, for Geminos wrote:
It is generally believed that Sirius produces the heat of the dog days; but this is an error, for the star merely marks a season of the year when the sun's heat is the greatest.
But he was an astronomer.
The idea prevailed, however, even with the sensible Dante in his "great scourge of days canicular"; while Milton, in Lycidas, designated it as "the swart star." And the notion holds good with many even to the present time. This character doubtless is indicated on the Farnese globe, where the Dog's head is surrounded with sun-rays.
But Pliny took a kinder view of this star, as in the "xii. chapyture of the xi. booke of his naturall hystorie," [XI.XII.30] on the origin of honey:
This coometh from the ayer at the rysynge of certeyne starres, and especially at the rysynge of Sirius, and not before the rysynge of Vergiliae (which are the seven starres cauled Pleiades) in the sprynge of the day;
although he seems to be in doubt whether "this bee the swette of heaven, or as it were a certeyne spettyl of the starres." This idea is first seen in Aristotle's History of Animals. So, too, in late astrology wealth and renown were the happy lot of all born under this and its companion Dog. Our modern Willis wrote in his Scholar of Thebet ben Khorat:
Mild Sirius tinct with dewy violet,
Set like a flower upon the breast of Eve.
When in opposition Sirius was supposed to produce the cold of winter.
It has been in all history the brightest star in the heavens, thought worthy by Pliny of a place by itself among the constellations, and even seen in broad sunshine with the naked eye by Bond at Cambridge, Massachusetts, and by others at midday with very slight optical aid; but its color is believed by many to have changed from red to its present white. This question recently has been discussed, by See in the affirmative and Schiaparelli in the negative, at a length not allowing repetition here, the weight of argument, however, seeming to be against the admission of any change of color in historic times.
Aratos' term ποικίλος, applied to the Dog, is equally appropriate to Sirius now in the sense of many-colored or changeful, and is an admirable characterization, as one realizes when watching this magnificent object coming up from the horizon on a winter evening. Tennyson, who is always correct as well as poetical in his astronomical allusions, says in The Princess:
the fiery Sirius alters hue
And bickers into red and emerald;
this, of course, being largely due to its marked scintillation; and Arago gave Barāḳish as an Arabic designation for Sirius, meaning Of a Thousand Colors; and said that as many as thirty changes of hue in a second had been observed in it. Montigny's scintillometer has marked as many as seventy-eight changes in a second in various white stars standing 30° above the horizon, though a somewhat less number in those of other colors.
Sirius, notwithstanding its brilliancy, is by no means the nearest star to our system, although it is among the nearest; only two or three others having, so far as is yet known, a smaller distance. Investigations up to the present time show a parallax of 0ʺ.39, indicating a distance of 8.3 light years, nearly twice that of α Centauri.
Some are of the opinion that the apparent magnitude of Sirius is partly due to the whiteness of its tint and its greater intrinsic brilliancy; and that the red stars, Aldebaran, Betelgeuze, and others, would appear much brighter than now if of the same color as Sirius; rays of red light affecting the retina of the eye more slowly than those of other colors. The modern scale of magnitudes that makes this star ‑1.43, — about 9 1/2 times as bright as the standard 1st-magnitude star Altair (α Aquilae), — would make the sun ‑25.4, or 7000 million times as bright as Sirius; but, taking distance into account, we find that Sirius is really forty times brighter than the sun.
Its spectrum, as type of the Sirian in distinction from the Solar, gives name to one of the four general divisions of stellar spectra instituted by Secchi from his observations in 1863‑67; these two divisions including nearly 11/12 of the observed stars. Of these about one half are Sirian of a
brilliantly white colour, sometimes inclining towards a steely blue. The sign manual of hydrogen is stamped upon them with extraordinary intensity
by broad, dark shaded lines which form a regular series.
It is found by Vogel to be approaching our system at the rate of nearly ten miles a second, and, since Rome was built, has changed its position by somewhat more than the angular diameter of the moon.
It culminates on the 11th of February.
The celebrated Kant thought that Sirius was the central sun of the Milky Way; and, eighteen centuries before him, the poet Manilius said that it was "a distant sun to illuminate remote bodies," showing that even at that early day some had knowledge of the true character and office of the stars.
Certain peculiarities in the motion of Sirius led Bessel in 1844, after ten years of observation, to the belief that it had an obscure companion with which it was in revolution; and computations by Peters and Auwers led Safford to locating the position of the satellite, where it was found as predicted on the 31st of January, 1862, by the late Alvan Clark,4 at Cambridgeport, Mass., while testing the 18 1/2-inch glass now at the Dearborn Observatory. It proved to be a yellowish star, estimated as of the 8 1/2 magnitude, but difficult to be seen because of the brilliancy of Sirius, and then 10ʺ away; this diminishing to 5ʺ in 1889; and last seen and measured by Burnham at the Lick Observatory before its final disappearance in April, 1890. Its reappearance was observed from the same place in the autumn of 1896 at a distance of 3ʺ.7, with a position angle of 195°. It has a period of 51 1/2 years, and an orbit whose diameter is between those of Uranus and Neptune; its mass being one third that of Sirius and equal to that of our sun, although its light is but 1/10000 its principal, soº that it may be supposed to be approaching non-luminous solidity, — one of Bessel's "dark stars."
It is remarkable that Voltaire in his Micromegas of 1752, an imitation of Gulliver's Travels, followed Dean Swift's so‑called prophetic discovery of the two moons of Mars by a similar discovery of an immense satellite of Sirius, the home of his hero. Swift, however, owed his inspiration to Kepler, who more than a century previously wrote to Galileo:
I am so far from disbelieving in the existence of the four circumjovial planets, that I long for a telescope to anticipate you, if possible, in discovering two round Mars (as the proportion seems to me to require), six or eight round Saturn, and perhaps one each round Mercury and Venus.
Other stars are shown by the largest glasses in the immediate vicinity of Sirius, two additional having very recently been discovered by Barnard at the Yerkes Observatory.

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