Part 19 (1/2)
”Dixit et antiqui monumenta perennia facti Anguis, Avis, Crater sidera, juncta mic.u.n.t.”
The star a Crateris was rated 4th magnitude by Al-Sufi and all other observers, and the Harvard measures make it 420, a satisfactory agreement. It has three companions noted by Admiral Smyth. One of these he called ”intense blood colour.” This is R Crateris, now known to be variable from above the 8th magnitude to below the 9th. Sir John Herschel called it an ”intense scarlet star, a curious colour.” With 3-inch refractor in the Punjab I found it ”full scarlet.” It is one of an open pair, the further of the two from a. There is a third star about 9th magnitude a little south of it. Ward saw a 13th magnitude star between a and R with a 2?-inch (Wray) refractor. This I saw ”readily” with my 3-inch. Smyth does not mention this faint star, although he used a much larger telescope.
Corvus, the Crow, is a small constellation, north of Hydra. Aratus says ”the Crow form seems to peck the fold of the water snake” (Hydra). The victory which Valerius Corvinus is said to have owed to a crow has given it the name of Pomptina, because the victory took place near the Pontine marshes.[446] A quadrilateral figure is formed by its four brightest stars, ?, d, , and e Corvi. This figure has sometimes been mistaken for the Southern Cross by those who are not familiar with the heavens. But the stars of the Southern Cross are much brighter.
The constellation Centaurus, the Centaur, lies south of Hydra and Libra, and north of the Southern Cross. According to Dupuis, Centaurus represents the 3rd ”labour of Hercules,” his triumph over the Centaurs.[447] The Centaurs were supposed to be a people living in the vicinity of Mount Ossa, who first rode on horses. The constellation was also called Semivir, Chiron, Phobos, Minotaurus, etc. Al-Sufi says it ”is represented by the figure of an animal, of which the forepart is the upper part of a man from the head to end of the back, and its hinder part is the hinder part of a horse, from the beginning of the back to the tail. It is to the south of the Balance [Libra] turning its face towards the east, and the hinder part of the beast towards the west.”
Al-Sufi describes very clearly the four bright stars of the famous ”Southern Cross.” Owing to precession these stars were some 7 further north in the tenth century than they are at present, and they could have been all seen by Al-Sufi, when on the meridian. In the time of Ptolemy and Hipparchus, they were still further north, and about 5000 years ago they were visible in the lat.i.tude of London. Dante speaks of these four stars as emblematical of the four cardinal virtues, Justice, Temperance, Fort.i.tude, and Prudence.
Closely south-east of a and Crucis is the dark spot in the Milky Way known as the ”Coal Sack,” which forms such a conspicuous object near the Southern Cross. It was first described by Pinzon in 1499; and afterwards by Lacaille in 1755. Although to the naked eye apparently black, photographs show that it contains many faint stars, but, of course, much less numerous than in the surrounding regions. The dark effect is chiefly caused by contrast with the brilliancy of the Milky Way surrounding it.
Al-Sufi also mentions the bright stars a and Centauri which follow the Southern Cross. He says that the distance between them ”is four cubits,”
that is about 9 20', but it is less than this now. a has a large ”proper motion” of 3”67 per annum, and was farther from in Al-Sufi's time than it is at present. This, however, would not _wholly_ account for the difference, and Al-Sufi's over-estimate is probably due to the well-known effect by which the distance between two stars is _apparently_ increased when they are near the horizon. Several of Al-Sufi's distances between southern stars are over-estimated, probably for the same reason.
The constellation Lupus, the Wolf, is south of Libra and Scorpio. It lies along the western border of the Milky Way. According to ancient writers it represents Lycaon, King of Arcadia, a contemporary of Cecrops, who is said to have sacrificed human victims, and on account of his cruelty was changed into a wolf. Another fable is that it represents a wolf sacrificed by the Centaur Chiron. According to Brown, Lupus appears on the Euphratian planisphere discovered by George Smyth in the palace of Sennacherib. Al-Sufi called it _al-sabu_, ”the Wild Beast.” It was also called _al-fand_, ”the Leopard,” and _al-asada_, ”the Lioness.”
Ara, the Altar, lies south of Scorpio. According to ancient writers it represents an altar built by Vulcan, when the G.o.ds made war against the t.i.tans. It is called by Al-Sufi _al-midjman_, ”the Scent Box,” or ”the Altar.”
The little constellation Corona Australis, the Southern Crown, lies south and west of Sagittarius, east of Scorpio, and west of Telescopium. Aratus refers to the stars in Corona Australis as--
”Other few Before the Archer under his forefeet Led round in circle roll without a name.”[449]
But the constellation was known by the names Caduceus, Orbiculus, Corona Sagittarii, etc. The ancient poets relate that Bacchus placed this crown in the sky in honour of his mother Semele.[450] Others say that it represents the crown conferred on Corinne of Thebes, famous as a poet.
The small constellation Piscis Australis, or the Southern Fish, lies south of Capricornus and Aquarius. In the most ancient maps it is represented as a fish drinking the water which flows from the urn of Aquarius.
A good many constellations have been added to the heavens since the days of Al-Sufi, and notes on some of these may be of interest.
CAMELOPARDALIS.--This constellation first appears on a celestial planisphere published by Bartschius in the year 1624. It was not formed by Bartschius himself, but by the navigators of the sixteenth century. It lies south of Ursa Minor, north of Perseus and Auriga, east of Draco, and west of Ca.s.siopeia. It contains no star brighter than the 4th magnitude.
LYNX.--This constellation is south of Camelopardalis and Ursa Major, and north of Gemini and Cancer. It was formed by Hevelius in 1660, and he called it the Lynx, because, he said, it contained only faint stars and ”it was necessary to have the eyes of a lynx” to see them! Some of them were, however, observed by Ptolemy and Al-Sufi, and are mentioned by the latter under Ursa Major.
CANES VENATICI, or the Hunting Dogs.--This was formed by Hevelius in 1660.
It lies south of the Great Bear's tail, north of Coma Berenices, east of Ursa Major, and west of Bootis. Its brightest stars a (12) and (8) were observed by Al-Sufi, and included by him in the ”extern” stars of Ursa Major.
COMA BERENICES.--This constellation lies between Canes Venatici and Virgo.
Although it was not included among the old forty-eight constellations of Ptolemy, it is referred to by Al-Sufi as the Plat, or Tress of Hair, and he included its stars Flamsteed 12, 15, and 21 in the ”extern” stars of Leo. It was originally formed by the poet Callimachus in the third century B.C., but was not generally accepted until reformed by Hevelius.
Callimachus lived at Alexandria in the reigns of Ptolemy Philadelphus and Ptolemy Euergetes, and was chief librarian of the famous library of Alexandria from about B.C. 260 until his death in B.C. 240. Eratosthenes was one of his pupils. The history of the constellation is as follows: Berenice, wife of Ptolemy Euergetes, made a vow, when her husband was leaving her on a military expedition, that if he returned in safety she would cut off her hair and consecrate it in the temple of Mars. Her husband returned, and she fulfilled her vow. But on the next day the hair had disappeared--stolen from the temple--and Conon the mathematician showed Ptolemy seven stars near the constellation of the Lion which did not belong to any constellation. These were formed into a constellation and called Berenice's Hair. Conon is referred to by Catullus in the lines--
”Idem me ille Conon cleste numine vidit E. Berenico vertice Caesariem.”
Coma Berenices first occurs as a distinct constellation in the catalogue contained in the Rudolphine Tables formed by Kepler (epoch 1600) from the observations of Tycho Brahe.[451] Bayer subst.i.tuted a sheaf of corn, an idea derived from an ancient ma.n.u.script.
LEO MINOR.--This small constellation lies between Ursa Major and Leo, and east of the Lynx. It was formed by Halley about the year 1660; but is referred to by Al-Sufi, who includes one of its stars (Fl. 41) in the ”extern” stars of Leo. There are, however, several brighter stars in the group. The brightest, Fl. 46, was measured 392 at Harvard. The star Fl.
37 was called _praecipua_ (or brightest) by Tycho Brahe, and rated 3, but as it was measured only 477 at Harvard it may possibly have diminished in brightness.
s.e.xTANS.--This constellation lies south of Leo, and north and east of Hydra. It was formed by Hevelius about the year 1680. According to the Harvard photometric measures its brightest star is Fl. 15 (450).
MONOCEROS, or the Unicorn, lies south of Gemini and Canis Minor, north of Canis Major and Argo, east of Orion, and west of Hydra. It appears on the planisphere of Bartschius, published in 1624. According to Scaliger it is shown on an old Persian sphere. One of its stars, Fl. 22, is mentioned by Al-Sufi among the ”extern” stars of Canis Major (No. 1). Another, Fl. 30, is given under Hydra (”Extern” No. 1) and Fl. 8, 13, and 15 are apparently referred to in Gemini. The star 15 Monocerotis is a little south of ?