According to Al-Sufi, the Arabians called Sirius al-schira al-abûr, “Sirius which has passed across,” also al-schira al Jamânija, “the Sirius of Yémen.” He says it is called al-abûr, “because it has passed across the Milky Way into the southern region.” He relates a mythological story why Sirius “fled towards the south” and passed across the Milky Way towards Suhail (Canopus). The same story is told by Albufaragius[439] (thirteenth century). (The story was probably derived from Al-Sufi.) Now, it seems to me a curious and interesting fact that the large proper motion of Sirius would have carried it across the Milky Way from the eastern to the western border in a period of 60,000 years. Possibly the Arabian story may be based on a tradition of Sirius having been seen on the opposite, or eastern, side of the Milky Way by the men of the early Stone Age. However this may be, we know from the amount and direction of the star’s proper motion that it must have passed across the Milky Way from east to west within the period above stated. The Arabic name al-abûr is not, therefore, a merely fanciful one, but denotes an actual fact. The proper motion of Sirius could not possibly have been known to the ancients, as it was only revealed by accurate modern observations.
The little constellation Canis Minor, the Little Dog, lies south of Gemini and Cancer. Small as it is, it was one of the original forty-eight constellations of Ptolemy. In the Greek mythology it was supposed to represent either one of Diana’s hunting dogs, or one of Orion’s hounds. Ovid calls it the dog of Icarus. Others say it was the dog of Helen, who was carried off by Paris. According to the old poets, Orion’s dog, or the dog of Icarus, threw himself into a well after seeing his master perish. The name Fovea, given to the constellation by Bayer, signifies a pit where corn was deposited. This comes from the fact that the rising of the star Procyon (α Canis Minoris) indicated the season of abundance. But Lalande thought it more probable that the idea of a pit came from the Greek σειρὸς, which means a corn store, and that it was confounded with Sirius.
The name of the bright star Procyon (α Canis Minoris) is derived from the Greek προκύων, “the advanced day,” because it appeared in the morning sky before Sirius. Procyon was called by the Hindoos Hanouman after their famous monkey god, from whose tail a bridge is said to have been formed to enable the army of Rama to pass from India to Ceylon. Al-Sufi says that the star was marked on the old astrolabes as al-schira al-schamia, “the Syrian Sirius.” It was also called, he says, al-schira al-gumaisa, “the Sirius with blear eyes” (!) from weeping because Sirius had passed across the Milky Way, Procyon remaining on the eastern side. Here we have the same legend again. The proper motion of Procyon (about the same in amount and direction as that of Sirius) shows that the star has been on the eastern side of the Milky Way for many ages past. About 60,000 years hence, Procyon will be near the star θ Canis Majoris, and will then—like Sirius—have passed across the Milky Way.
Argo, the Ship, is a large constellation south of Hydra, Monoceros, and Canis Major. It is called by Al-Sufi al-safîna, “the Ship.” It is supposed to represent the first ship ever built. The name is derived from the builder Argo, or from the Greek word ’Αργὸς. This ship is said to have been built in Thessaly by order of Minerva and Neptune, to go on the expedition for the conquest of the golden fleece. The date of this expedition, commanded by Jason, is usually fixed at 1300 or 1400 B.C. With reference to the position of this supposed ship in the sky, Proctor says, “It is noteworthy that when we make due correction for the effects of precession during the past 4000 years, the old constellation Argo is set on an even keel, instead of being tilted some 45° to the horizon, as at present when due south.” He connects Argo with Noah’s Ark.
The brightest star of Argo is Canopus, called Suhaïl by Al-Sufi. It is the second brightest star in the heavens; but it is not visible in northern latitudes. The Harvard photometric measures make it nearly one magnitude brighter than the zero magnitude, about two magnitudes brighter than Aldebaran, and about half the brightness of Sirius. This fine star has been suspected of variable light. Webb says, “It was thought (1861) in Chili brighter than Sirius.” Observing it in the Punjab, the present writer found it on several occasions but little inferior to Sirius, although very low on the southern horizon. From recent observations by Mr. H. C. McKay in Australia, he believes that it is variable to the extent of at least half a magnitude.[440] But it is difficult to establish variations of light in very bright stars. The parallax of Canopus is very small, so its distance from the earth is very great, and it must be a sun of gigantic size. According to Al-Fargani, Canopus was called the star of St. Catherine by the Christian pilgrims in the tenth century.[441] It was called Suhaïl by the old Arabians, a name apparently derived from the root sahl, “a plain”; and Schjellerup suggests that the name was probably applied to this and some other southern stars because they seem to move along a plain near the southern horizon. Al-Sufi says that he measured the latitude of Schiraz in Persia, where he observed, and found it to be 29° 36′; and hence for that place Canopus, when on the meridian, had an altitude of about 9°. Canopus was the ancient name of Aboukir in Egypt, and is said to have derived its name from the pilot of Menelaus, whose name was Kanobus, and who died there from the bite of a snake. The star is supposed to have been named after him, and it was worshipped by the ancient Egyptians.
Al-Sufi does not mention the famous variable star η Argûs, which, owing to the precession of the equinoxes, he might possibly have seen close to the horizon, if it had been a bright star in his day. It lies between φ Velorum and α Crucis. Both of these stars are mentioned by Al-Sufi, but he says nothing of any bright star (or indeed any star) between them. This negative evidence tends to show that η Argûs was not visible to the naked eye in Al-Sufi’s time. This extraordinary star has in modern times varied through all degrees of brightness from Sirius down to the 8th magnitude! Schönfeld thought that a regular period is very improbable. It seems to be a sort of connecting link between the long period variables and the novæ or temporary stars. It is reddish in colour, and the spectrum of its light is very similar to that of the temporary stars. Whether it will ever become a brilliant object again, time alone can tell; but from the fact that it was presumably faint in Al-Sufi’s time, and afterwards increased to the brightness of Sirius, it seems possible that its light may again revive.
The long constellation Hydra lies south of Cancer, Leo, Crater, Corvus, Virgo, and Libra. It was also called Asina, Coluber, Anguis, Sublimatus, etc. In the Greek mythology it was supposed to represent the Lernæan serpent killed by Hercules. According to Ovid, who fixed its acronycal rising for February 14, it had a common origin with Corvus and Crater. Apollo, wishing to sacrifice to Jupiter, sent the Crow with a cup to fetch water. On his way to the well the Crow stopped at a fig tree and waited for the fruit to ripen! Afterwards, to excuse his delay, he said that a serpent had prevented him from drawing the water. But Apollo, to punish the Crow for his deception, changed his plumage from white to black, and ordered the serpent to prevent the Crow from drinking.[442] Hydra was called by Al-Sufi al-schudja, “the Serpent, or Hydra.” He says that “it contains twenty-five stars in the figure and two ‘outside’, and its head is to the south of the southern scale of the Balance” (α Libræ). But this is clearly a mistake (one of the very few errors to be found in Al-Sufi’s work), for he goes on to say that the head is composed of four stars forming a figure like the head of a horse, and he adds, “This head is in the middle between al-shira al-gumaisa [Procyon] and Kalb al-asad [Regulus] the Heart, inclining from these two stars a little to the south.” This clearly indicates the stars δ, ε, η, and σ Hydræ which, with ζ Hydræ, have always been considered as forming the Hydra’s head. These stars lie south of α and β Cancri, not south of Libra as Al-Sufi says (doubtless by a slip of the pen).
Ptolemy’s 12th star of Hydra (α Hydræ) is, Al-Sufi says, “the bright red star which is found at the end of the neck where the back begins; it is of the 2nd magnitude. It is that which is marked on the astrolabe as unk al-schudja, ‘the neck of the serpent,’ also al-fard, ‘the solitary one.’” Al-Sufi’s estimate of its brightness agrees well with modern measures; but it has been suspected of variable light. Sir John Herschel’s estimates at the Cape of Good Hope varied from 1·75 to 2·58 magnitude. He thought that its apparent variation might be due to its reddish colour, and compares it to the case of α Cassiopeiæ. But as this latter star is now known to be irregularly variable it seems probable that α Hydræ may be variable also. Gemmill found it remarkably bright on May 9, 1883, when he thought it nearly equal to Pollux (1·2 magnitude). On the other hand, Franks thought it nearer the 3rd than the 2nd magnitude on March 2, 1878. On April 9, 1884, the present writer found it only slightly less than Regulus (1·3 magnitude). On April 6, 1886, how-ever, it was considerably less than Regulus, but half a magnitude brighter than β Canis Minoris, or about 2½ magnitude. In the Chinese Annals it is called the “Red Bird.” In a list of thirty stars found on a tablet at Birs-Nimroud, it is called “The son of the supreme temple.” Although to the naked eye deserving the name of Alphard or “the solitary one,” it is by no means an isolated star when examined with a telescope. It has a faint and distant companion, observed by Admiral Smyth; and about 25′ to the west of it Ward saw a small double star (8, 13: 90°: 50″). With a 3-inch refractor in the Punjab, I saw a small star of about 8½ magnitude to the south and a little east of the bright star, probably identical with Smyth’s companion. Farther off in the same direction I saw a fainter star, and others at greater distances in the field. There is also a faint star a little to the north. I also saw Ward’s double with the 3-inch telescope.
There is some difficulty in identifying the stars numbered by Ptolemy 13, 14, and 15 in Hydra. Having plotted a map from Ptolemy’s positions (as given by Al-Sufi), I have come to the conclusion that Ptolemy’s stars are 13 = κ Hydræ; 14 = υ; and 15 = λ Hydræ, probably. From the clear description given by Al-Sufi of the stars observed by him, I find that his stars are 13 = υ1; 14 = υ2; and 15 = λ Hydræ. We must, therefore, conclude that Ptolemy and Al-Sufi saw only three stars where now there are four,[443] and that κ Hydræ was not seen, or at least is not mentioned by Al-Sufi. κ is, therefore, probably variable. It was rated 4 by Tycho Brahé, Bayer, and Hevelius; it is at present about 5th magnitude. If Ptolemy did not see υ2 it is probably variable also, and, indeed, it has been suspected of variable light.[444]
The small constellation of Crater, the Cup, lies north of Hydra, and south of Leo and Virgo. Al-Sufi calls it al-batija, “the Jar, or Cup.” He says the Arabians called it al-malif, “the Crib, or Manger.” According to Brown, the stars of Crater exactly form a Bakhian κάνθαρος, with its two handles rising above the two extremities of the circumference.[445] An Asia Minor legend “connected Crater with the mixing of human blood with wine in a bowl.” Crater is referred to by Ovid in the lines—