Part 16 (1/2)
These old Arabic names seem very fanciful.
Al-Sufi relates that in the year 337 of the Hegira (about A.D. 948) he went to Ispahan with Prince Abul-fadhl, who introduced him to an inhabitant of that city, named Varvadjah, well known in that country, and famous for his astronomical acquirements. Al-Sufi asked him the names of the stars on an astrolabe which he had, and he named Aldebaran, the two bright stars in the Twins (Castor and Pollux), Regulus, Sirius, and Procyon, the two Simaks, etc. Al-Sufi also asked him in what part of the sky _Al-fard_ (a Hydrae) was, but he did not know! Afterwards, in the year 349, this same man was at the court of Prince Adhad-al-Davlat, and in the presence of the Prince, Al-Sufi asked him the name of a bright star--it was _al-nasr al-vaki_, the falling Vulture (Vega), and he replied, ”That is _al-aijuk_” (Capella)! thus showing that he only knew the _names_ of the stars, but did not know them when he saw them in the sky. Al-Sufi adds that all the women ”who spin in their houses” knew this star (Vega) by the name of _al-atsafi_, the Tripod. But this could not be said even of ”educated women” at the present day.
With reference to the number of stars which can be seen with the naked eye, Al-Sufi says, ”Many people believe that the total number of fixed stars is 1025, but this is an evident error. The ancients only observed this number of stars, which they divided into six cla.s.ses according to magnitude. They placed the brightest in the 1st magnitude; those which are a little smaller in the 2nd; those which are a little smaller again in the 3rd; and so on to the 6th. As to those which are below the 6th magnitude, they found that their number was too great to count; and this is why they have omitted them. It is easy to convince one's self of this. If we attentively fix our gaze on a constellation of which the stars are well known and registered, we find in the s.p.a.ces between them many other stars which have not been counted. Take, for example, the Hen [Cygnus]; it is composed of seventeen internal stars, the first on the beak, the brightest on the tail, the others on the wings, the neck and the breast; and below the left wing are two stars which do not come into the figure. Between these different stars, if you examine with attention, you will perceive a mult.i.tude of stars, so small and so crowded that we cannot determine their number. It is the same with all the other constellations.” These remarks are so correct that they might have been written by a modern astronomer.
It should be added, however, that _all_ the faint stars referred to by Al-Sufi--and thousands of others still fainter--have now been mapped down and their positions accurately determined.
About the year 1437, Ulugh Beigh, son of Shah Rokh, and grandson of the Mogul Emperor Tamerlane, published a catalogue of stars in which he corrected Ptolemy's positions. But he seems to have accepted Al-Sufi's star magnitudes without any attempt at revision. This is unfortunate, for an _independent_ estimate of star magnitudes made in the fifteenth century would now be very valuable for comparison with Al-Sufi's work and with modern measures. Ulugh Beigh's catalogue contains 1018 stars, nearly the same number as given by Ali-Sufi.[393]
CHAPTER XIX
The Constellations[394]
Curious to say, Al-Sufi rated the Pole Star as 3rd magnitude; for it is now only slightly less than the 2nd. At present it is about the same brightness as of the same constellation (Ursa Minor) which Al-Sufi rated 2nd magnitude. It was, however, also rated 3rd magnitude by Ptolemy (or Hipparchus), and it may possibly have varied in brightness since ancient times. Admiral Smyth says that in his time (1830) it was ”not even a very bright third size” (!)[395] Spectroscopic measures show that it is approaching the earth at the rate of 16 miles a second; but this would have no perceptible effect on its brightness in historical times. This may seem difficult to understand, and to some perhaps incredible; but the simple explanation is that its distance from the earth is so great that a journey of even 2000 years with the above velocity would make no _appreciable_ difference in its distance! This is undoubtedly true, as a simple calculation will show, and the fact will give some idea of the vast distance of the stars. The well-known 9th magnitude companion to the Pole Star was seen _by day_ in the Dorpat telescope by Struve and Wrangel; and ”on one occasion by Encke and Argelander.”[396]
The star Ursae Minoris was called by the Arabians _Kaukab al-shamali_, the North Star, as it was--owing to the precession of the Equinoxes--nearer to the Pole in ancient times than our present Pole Star was _then_.
The ”Plough” (or Great Bear) is supposed to represent a waggon and horses.
”Charles' Wain” is a corruption of ”churl's wain,” or peasant's cart. The Arabians thought that the four stars in the quadrilateral represented a bier, and the three in the ”tail” the children of the deceased following as mourners! In the Greek mythology, Ursa Major represented the nymph Callisto, a daughter of Lycaon, who was loved by Jupiter, and turned into a bear by the jealous Juno. Among the old Hindoos the seven stars represented the seven Ris.h.i.+s. It is the Otawa of the great Finnish epic, the ”Kalevala.” It was also called ”David's Chariot,” and in America it is known as ”The Dipper.”
Closely north of the star ? in Ursa Major is a small star known as Flamsteed 26. This is not mentioned by Al-Sufi, but is now, I find from personal observation, very visible, and indeed conspicuous, to the naked eye. I find, however, that owing to the large ”proper motion” of the bright star (1”1 per annum) the two stars were much closer together in Al-Sufi's time than they are at present, and this probably accounts for Al-Sufi's omission. This is an interesting and curious fact, and shows the small changes which occur in the heavens during the course of ages.
Close to the star ?, the middle star of the ”tail” of Ursa Major (or handle of the ”Plough”), is a small star known as Alcor, which is easily visible to good eyesight without optical aid. It is mentioned by Al-Sufi, who says the Arabians called it _al-suha_, ”the little unnoticed one.” He says that ”Ptolemy does not mention it, and it is a star which seems to test the powers of the eyesight.” He adds, however, an Arabian proverb, ”I show him _al-suha_, and he shows me the moon,” which seems to suggest that to some eyes, at least, it was no test of sight at all. It has, however, been suspected of variation in light. It was rated 5th magnitude by Argelander, Heis, and Houzeau, but was measured 402 at Harvard Observatory. It has recently been found to be a spectroscopic binary.
The constellation of the Dragon (Draco) is probably referred to in Job (chap. xxvi. v. 13), where it is called ”the crooked serpent.” In the Greek mythology it is supposed to represent the dragon which guarded the golden apples in the Garden of the Hesperides. Some have suggested that it represented the serpent which tempted Eve. Dryden says, in his translation of Virgil--
”Around our Pole the spiry Dragon glides, And like a wand'ring stream the Bears divides.”
The fact that the constellation Bootis rises quickly and sets slowly, owing to its lying horizontally when rising and vertically when setting, was noted by Aratus, who says--
”The Bearward now, past seen, But more obscured, near the horizon lies; For with the four Signs the Ploughman, as he sinks, The deep receives; and when tired of day At even lingers more than half the night, When with the sinking sun he likewise sets These nights from his late setting bear their name.”[397]
The cosmical setting of Bootis--that is, when he sets at sunset--is stated by Ovid to occur on March 5 of each year.
With reference to the constellation Hercules, Admiral Smyth says--
”The kneeling posture has given rise to momentous discussion; and whether it represents Lycaon lamenting his daughter's transformation, or Prometheus sentenced, or Ixion ditto, or Thamyrus mourning his broken fiddle, remains still uncertain. But in process of time, this figure became a lion, and Hyginus mentions both the lion's skin and the club; while the right foot's being just over the head of the Dragon, satisfied the mythologists that he was crus.h.i.+ng the Lernaean hydra.... Some have considered the emblem as typifying the serpent which infested the vicinity of Cape Taenarus, whence a sub-genus of Ophidians still derives its name. At all events a poet, indignant at the heathen exaltation of Hevelius, has said--
”'To Cerberus, too, a place is given-- His home of old was far from heaven.'”[398]
Aratus speaks of Hercules as ”the Phantom whose name none can tell.”
There were several heroes of the name of Hercules, but the most famous was Hercules the Theban, son of Jupiter and Alcmene wife of Amphitryon, King of Thebes, who is said to have lived some years before the siege of Troy, and went on the voyage of the Argonauts about 1300 B.C. According to some ancient writers, another Hercules lived about 2400 B.C., and was a contemporary of Atlas and Theseus. But according to Petau, Atlas lived about 1638 B.C., and Lalande thought that this chronology is the more probable.
The small constellation Lyra, which contains the bright star Vega, is called by Al-Sufi the Lyre, the Goose, the Persian harp, and the Tortoise.
In his translation of Al-Sufi's work, Schjellerup suggests that the name ”Goose” may perhaps mean a plucked goose, which somewhat resembles a Greek lyre, and also a tortoise. The name of the bright star Vega is a corruption of the Arabic _vaki_. Ptolemy and Al-Sufi included all the very brightest stars in the ”first magnitude,” making no distinction between them, but it is evident at a glance that several of them, such as Arcturus and Vega, are brighter than an average star of the first magnitude, like Aldebaran.
The constellation Perseus, which lies south-east of ”Ca.s.siopeia's Chair,”
may be recognized by the festoon formed by some of its stars, the bright star a Persei being among them. It is called by Al-Sufi ”_barschansch_, ?e?se??, Perseus, who is _hamil ras al-gul_, the Bearer of the head of _al-gul_.” According to Kazimirski, ”_Gul_ was a kind of demon or ogre who bewilders travellers and devours them, beginning at the feet. In general any mischievous demon capable of taking all sorts of forms.” In the Greek mythology Perseus was supposed to be the son of Jupiter and Danae. He is said to have been cast into the sea with his mother and saved by King Polydectus. He afterwards cut off the head of Medusa, one of the Gorgons, while she slept, and armed with this he delivered Andromeda from the sea-monster.
The constellation Auriga lies east of Perseus and contains the bright star Capella, one of the three brightest stars in the northern hemisphere (the others being Arcturus and Vega). Theon, in his commentary on Aratus, says that Bellerophon invented the chariot, and that it is represented in the heavens by Auriga, the celestial coachman. According to Dupuis, Auriga represents Phaeton, who tried to drive the chariot of the sun, and losing his head fell into the river Erida.n.u.s. The setting of Erida.n.u.s precedes by a few minutes that of Auriga, which was called by some of the ancient writers Amnis Pha-tontis.[399] Auriga is called by Al-Sufi _numsick al-ainna_--He who holds the reins, the Coachman; also _al-inaz_, the She-goat. M. Dorn found in Ptolemy's work, the Greek name ???????, Auriga, written in Arabic characters. Al-Sufi says, ”This constellation is represented by the figure of a standing man behind 'He who holds the head of _al-gul_' [Perseus], and between the Pleiades and the Great Bear.”