Astronomical Curiosities: Facts and Fallacies

According to Houzeau, Libra was formed at the beginning of the second century B.C., and it does not appear in any writings before those of Geminus and Varron.415

Milton says in Paradise Lost: —

“The Eternal to prevent such horrid fray,Hung forth in heaven his golden scales, yet seenBetwixt Astræa and the Scorpion’s sign.”

(Here Astræa is Virgo.)

It is worth noticing that both Ptolemy and Al-Sufi rated the star κ Libræ as two magnitudes brighter than λ Libræ. The two stars are now practically of equal brightness (5th magnitude), and it seems impossible to believe that this could have been the case in Al-Sufi’s time. Surely a careful observer like Al-Sufi, who estimated the relative brightness of stars to a third of a magnitude, could not possibly have made an error of two magnitudes in the brightness of two stars near each other! It should be stated, however, that κ Libræ was rated 5th magnitude by Argelander and Heis, and λ, 6th magnitude by the same excellent observers.

The next “sign” of the Zodiac, Scorpion, was consecrated by the Romans to Mars, and by the Egyptians to Typhon.416 It was called Nepa by Cicero, Martis sidus by Manilius, and Fera magna by Aratus. The Greek name was πάχον.

Mr. E. B. Knobel has called attention to a curious remark of Ptolemy with reference to the bright star Antares (α Scorpii), “Media earum quæ tendit ad rapinam quæ dicitur Cor Scorpionis”; and he made a similar remark with reference to Betelgeuse (α Orionis) and others. But Mr. Robert Brown417 explains the remark by the fact that in ancient times these stars rose in the morning at a time when caravans were exposed to dangers from robbers. Thus the term had nothing to do with the aspect or colour of these stars, but was merely a reference to their supposed astrological influence on human affairs.

In the Egyptian Book of the Dead, Silkit was a goddess who assumed the form of a scorpion in the sky. She was supposed to be the daughter of Ra.

With reference to stars “outside” the ancient figure of Scorpio, the first, Al-Sufi says, “is a star which immediately follows al-schaulat” [λ] and κ, “it is of small 4th magnitude; Ptolemy calls it νεφελοείδης” [nebulous]. Schjelerup, in his translation of Al-Sufi’s work, does not identify this object; but it is very evidently γ Telescopii, which lies exactly in the position described by Al-Sufi. Now, it is a very interesting and curious fact that Ptolemy called it nebulous, for in the same telescopic field with it is the nebula h 3705 (= Dunlop 557). Dunlop describes it as a “small well-defined rather bright nebula, about 20″ in diameter; a very small star precedes it, but is not involved; following γ Telescopii.” Sir John Herschel at the Cape found it fairly resolved into very faint stars, and adds, “The whole ground of the heavens, for an immense extent is thickly sown with such stars. A beautiful object.”418 This perhaps accounts for the nebulous appearance of the star as seen by Ptolemy.

Several novæ or temporary stars are recorded as having appeared in Scorpio. One in the year B.C. 134 is stated by Pliny to have induced Hipparchus to form his catalogue of stars. This star was also observed in China. Its exact position is unknown, but Flammarion thinks it may possibly have appeared about 4° north of the star β Scorpii. Another new star is said to have appeared in A.D. 393, somewhere in the Scorpion’s tail. One in A.D. 1203 and another in 1584 are also mentioned, the latter near π Scorpii.

The constellation Scorpio seems to be referred to by Dante in his Purgatorio (ix. 4-6) in the lines —

“De gemma la sua fronte era lucentaPoste in figura del fredda animaleChe con la coda percota la genta,”

perhaps suggested by Ovid’s remark —

“Scorpius exhibit caudaque menabitur unca.”419

Next to Scorpio comes Sagittarius, the Archer. It is said to have been placed in the sky as a symbol of Hercules, a hero who was held in the greatest veneration by the ancient Egyptians. The horse, usually associated with this constellation, was a symbol of war. It was also called by the ancients Chiron, Arcitenens, Minotaurus, Croton, etc. The Greek name was παυνί, or παωνί. Chiron was supposed to be the son of Saturn and Phillyra, and first taught men to ride on horses. The name is derived from the Greek χείρ, a hand. Some writers, however, think that Chiron is represented by the constellation of the Centaur, and others say that Sagittarius represents the Minotaur loved by Persephone. According to Dupuis, Sagittarius represents the 5th “labour of Hercules,” which consisted in hunting the birds of the lake Stymphalus, which ravaged the neighbouring countries. These birds are perhaps represented by Cygnus, Altair, and the Vulture (Lyra). The Lyre probably represents the musical instrument which Hercules used to frighten the birds.420

According to Al-Sufi, the Arabians called the stars γ, δ, ε, and η Sagittarii which form a quadrilateral figure, “the Ostrich which goes to the watering place,” because they compared the Milky Way to a river. They compared the stars σ, φ, τ, and ζ Sagittarii, which form another quadrilateral, to an ostrich which has drunk and returns from the “watering place.” He says that the star λ Sagittarii forms with these two “ostriches” a tent, and certainly the figure formed by λ, φ, ζ, ε, and δ is not unlike a tent. Al-Sufi says more about these “ostriches”; but the ideas of the old Arabians about the stars seem very fanciful.

A “temporary star” is recorded in the Chinese Annals of Ma-touan-lin as having appeared in May, B.C. 48, about 4° distant from μ Sagittarii. Another in the year 1011 A.D. appeared near the quadrilateral figure formed by the stars σ, τ, ζ, and φ Sagittarii. This may perhaps be identified with the object referred to by Hepidannus in the year 1012, which was of extraordinary brilliancy, and remained visible “in the southern part of the heavens during three months.” Another is mentioned near the same place in A.D. 386 (April to July).421 The number of “temporary stars” recorded in this part of the heavens is very remarkable.

According to Brown, Sagittarius is depicted on a stone, cir. B.C. 1100, found at Bâbilu, and now in the British Museum.422

The next of the “signs of the Zodiac” is Capricornus, the Goat. In the Arabo-Latin edition of Ptolemy’s Almagest it is called Alcaucurus. It is supposed to represent Amalthea, the goat which nursed Jupiter. According to Dupuis it represented the 6th “labour of Hercules,” which was the cleaning out of the Augean stables.423

α2 Capricorni is the northern of two stars of the 4th magnitude (α and β Capricorni). It really consists of two stars visible to the naked eye. The second of these two stars (α1) is not mentioned by Al-Sufi, but I find that, owing to proper motion, they were nearer together in his time (tenth century), and were evidently seen by him as one star. β Capricorni (about 3rd magnitude) is a very wide double star (3½, 6; 205″), which may be seen with any small telescope. The fainter star was found to be a close double by Burnham. At present β is brighter than α, although rated of the same brightness by Al-Sufi.

Aquarius is the next “sign of the Zodiac.” It is supposed to represent a man pouring water out of an urn or bucket. Other names given to this constellation were Aristæus, Ganymede, Cecrops, Amphora, Urna, and Aqua tyrannus. According to Dupuis it represents the 7th “labour of Hercules,” which was his victory over the famous bull which ravaged Crete.424 But the connection between a bull and a bucket is not obvious. Aquarius is represented in several places on the Egyptian monuments. Some of the ancient poets supposed that it represented Deucalion (the Noah of the Greek story of the Deluge); others thought that it represented Cecrops, who came to Greece from Egypt, built Athens, and was also called Bifornis. Others say that he was Ganymede, the cup-bearer of the gods.

There is some difficulty about the identification of some of Al-Sufi’s stars in Aquarius. His sixth star (Fl. 7) is nearly 10° south-west of β Aquarii, and is, Al-Sufi says, “the following of three stars in the left hand, and precedes the fourth [β] … it is of the 6th magnitude. Ptolemy calls it third, but in reality it is very faint” [now about 6th magnitude]. The seventh [μ] is the middle one of the three and about 4½ magnitude, although Al-Sufi calls it “small fifth” [Ptolemy rated it 4]. The eighth star, ε, is the preceding of the three and about 3·8, agreeing closely with Al-Sufi’s 4·3. Ptolemy rated it 3. This star is mentioned under the name nou in the time of Tcheou-Kong in the twelfth century B.C. Al-Sufi says, “These three stars are followed by a star of the 5th magnitude which Ptolemy has not mentioned. It is brighter than the sixth star” [Fl. 7]. This is evidently ν Aquarii. If, however, we plot Ptolemy’s positions as given by Al-Sufi, it seems probable that Ptolemy’s sixth star was really ν, and that either μ or Fl. 7 was not seen by him. As Ptolemy called his seventh star 4th magnitude, and his sixth and eighth stars 3rd magnitude, some considerable change of brightness seems to have taken place in these stars; as ν is now only 4½ and Fl. 7 only a bright sixth. Variation was suspected in Fl. 7425 by Gould. I found it very reddish with binocular in October, 1892. Burnham found it to be a close double star, the companion being about 12th magnitude at a distance of only 2″. It is probably a binary.

According to Al-Sufi, the Arabians called the second and third stars of the figure (α and ο Aquarii) sad al-malik (malk or mulk), “the Good Fortune of the king.” They called the fourth and fifth stars (β and ξ Aquarii) with the twenty-eighth star of Capricornus (c) sad al-sund, “the Good Fortune of the Happy Events.” “This is the 24th mansion of the moon.” These stars rose at the time of year when the cold ends, and they set at the time the heat ends. Hence, Al-Sufi says, “when they rise the rains begin, and when they set the unhealthy winds cease, fertility abounds, and the dew falls.” Hence probably the Arabic names. This, of course, applies to the climate of Persia and Arabia, and not to the British Isles. Al-Sufi says, “They call the 6th, 7th, and 8th stars sad bula, ‘The Good Fortune which swallows up!’ This is the 23rd mansion of the moon. They say that it is so called because that at the time of the Deluge it rose at the moment when God said, ‘O earth! absorb the waters’ (Koran, chap, xi., v. 46). They called the stars γ, π, ζ and η Aquarii sad al-achbija, ‘the the Good Fortune of the tents’; this is the 25th mansion of the moon, and they give them this name because of these four stars, three form a triangle, the fourth [ζ] being in the middle.” The three were considered to form a tent.

The Arabians called the bright star Fomalhaut “in the mouth of the southern fish al-dhifda al-auval, ‘the first Frog,’ as the bright one on the southern point of the tail of Kîtus [Cetus] is called al-dhifda al-tsani [β Ceti], ‘the second Frog.’” Fomalhaut was also called al-zhalim, “the male ostrich.”

Al-Sufi says, “Some of the Arabians state that a ship is situated to the south of Aquarius.” The stars in the Southern Fish (Piscis Australis) seem to be here referred to.

The constellation Pisces, the Fishes, is the last of the “signs of the Zodiac.” The Fishes appear on an ancient Greek obelisk described by Pococke. Among the Greeks this sign was consecrated to Venus; and in Egypt to Nepthys, wife of Typhon and goddess of the sea. Pisces is said to end the Zodiac as the Mediterranean Sea terminated Egypt. This idea was suggested by Schmidt, who also conjectured that the Ram (Aries) was placed at the beginning of the Zodiac because Thebes, a town sacred to Jupiter Ammon, was at the beginning of Egypt in ancient times; and he thought that the constellation Triangulum, the Triangle, represented the Nile Delta, Eridanus being the Nile.426 The constellation was represented in ancient times by two fishes connected by a cord tied to their tails. The southern of these “fishes” lies south of the “Square of Pegasus,” and the northern between Andromeda and Aries. According to Manilius, the origin of these fishes is as follows: Venus, seeing Typhon on the banks of the river Euphrates, cast herself with her son into the river and they were transformed into fishes!

Some of the Arabians substituted a swallow for the northern of the two fishes – the one below Andromeda. The swallow was a symbol of Spring. According to Dupuis, Pisces represents the 8th “labour of Hercules,” his triumph over the mares of Diomed which emitted fire from their nostrils.427 But the connection between fishes and mares is not obvious, and some of Dupuis’ ideas seem very fanciful. Here he seems to have found a “mare’s nest.”

The constellation Cetus, the Whale, represents, according to ancient writers, the sea monster sent by Neptune to devour Andromeda when she was chained to the rock. Aratus calls Cetus the “dusky monster,” and Brown remarks that “the ‘Dusky Star’ would be peculiarly appropriate to Mira (the wondrous ο Ceti).”428 Cetus was also called Canis Tritonis, or Dog of the Sea, Bayer in his Atlas (1603) shows a dragon instead of a whale, finding it so represented on some ancient spheres. Al-Sufi calls it Kîtus or κητος, the whale. He says, “it is represented by the figure of a marine animal, of which the fore part is turned towards the east, to the south of the Ram, and the hinder part towards the west behind the three ‘extern’ stars of Aquarius.”

Al-Sufi does not mention the variable star ο Ceti, now called Mira, or the “wonderful,” nor does he refer to any star in its immediate vicinity. We may, therefore, conclude that it was near a minimum of light at the time of his observation of the stars of Cetus.

The constellation of Orion, one of the finest in the heavens, was called by Al-Sufi al-djabbar, “the Giant,” and also al-djauza, “the Spouse.” The poet Longfellow says —

“Sirius was rising in the eastAnd, slow ascending one by one,The kindling constellations shoneBegirt with many a blazing starStood the great giant Al-gebarOrion, hunter of the beast!His sword hung gleaming at his sideAnd on his arm, the lion’s hide —Scattered across the midnight airThe golden radiance of its hair.”

Al-Sufi says it “is represented by the figure of a standing man, to the south of the sun’s path. This constellation very much resembles a human figure with a head and two shoulders. It is called al-djabbar, ‘the Giant,’ because it has two thrones, holds a club in his hand, and is girded with a sword.” Orion is supposed to have been a son of Neptune; but there are many stories of the origin of the name. It is also said to be derived from the Greek word ὤρα, because the constellation was used to mark the different times of the year. According to the ancient fable, Orion was killed by a scorpion, and was placed in the sky at the request of Diana. According to Houzeau, the name comes from oriri, to be born. Scorpio rises when Orion sets, and he thinks that the idea of the ancients was that the Scorpion in this way kills the giant Orion.

In ancient Egypt Orion was called Sahu. This name occurs on the monuments of the Ptolemies, and also on those of the Pharaohs. It is also mentioned in the Book of the Dead. It seems to have been considered of great importance in ancient Egypt, as its heliacal rising announced that of Sirius, which heralded the annual rising of the Nile.

The constellation Eridanus lies south of Taurus, east of Cetus, and west of Lepus. In ancient times it was supposed to represent the Nile or the Po. Ptolemy merely calls it Ποταμοῦ ἀστερισμὸς, or asterism of the river. It was called Eridanus by the Greeks, and Fluvius by the Romans. It appears to correspond with the Hebrew Shicor. Al-Sufi calls it al-nahr, “the River.”

One of the most interesting points in Al-Sufi’s most interesting work is the identity of the bright star known to the ancient astronomers as achir al-nahr, “the End of the River,” and called by Ptolemy ’Εσχατος τοῦ ποταμοῦ, “the Last in the River.” Some astronomers have identified this star with α Eridani (Achernar), a bright southern star of the 1st magnitude, south of Eridanus. But Al-Sufi’s description shows clearly that the star he refers to is really θ Eridani; and the reader will find it interesting to follow his description with a star map before him. Describing Ptolemy’s 34th star of Eridanus (the star in question), he says, “the 34th star is found before [that is west of] these three stars [the 31st, 32nd, and 33rd, which are υ2, Du, and υ′ in Proctor’s Atlas], the distance between it and that of the three which is nearest being about 4 cubits [9° 20′]. It is of the first magnitude; it is that which is marked on the southern astrolabe, and called achir al-nahr, ‘the End of the River.’ There are before this bright one two stars, one to the south, [σ Eridani, not shown in Proctor’s small Atlas], the other to the north [ι Eridani]; Ptolemy does not mention these. One of these stars is of the 4th magnitude, the other of the 5th. There is behind the same [that is, east of it] a star of the 4th magnitude distant from it two cubits [ε Eridani]. To the south of the three stars which follow the bright one there are some stars of the 4th and 5th magnitudes, which he [Ptolemy] has not mentioned.”

Now, a glance at a star map of this region will show clearly that the bright star referred to by Al-Sufi is undoubtedly θ Eridani, which is therefore the star known to the ancients as the “End of the River,” or the “Last in the River.”

The position given by Ptolemy agrees fairly well with Al-Sufi’s description, although the place is slightly erroneous, as is also the case with Fomalhaut and β Centauri. It is impossible to suppose that either Ptolemy or Al-Sufi could have seen α Eridani, as it is too far south to be visible from their stations, and, owing to the precession of the equinoxes, the star was still further south in ancient times. Al-Sufi says distinctly that the distance between Ptolemy’s 33rd star (which is undoubtedly h Eridani, or Proctor’s υ′) and the 34th star was “4 cubits,” or 9° 20′. The actual distance is about 9° 11′, so that Al-Sufi’s estimate was practically correct. Halley, in his Catalogus Stellarium Australium, identifies Ptolemy’s star with θ Eridani, and Baily agreed with him.429 Ulugh Beigh also identifies the “Last in the River” with θ Eridani. The Arabic observer Mohammed Ali Achsasi, who observed in the seventeenth century, called θ Eridani Achr al-nahr, and rated it first magnitude.430 To argue, as Bode and Flammarion have done, that Ptolemy and Al-Sufi may have heard of α Eridani from travellers in the southern hemisphere, is to beg the whole question at issue. This is especially true with reference to Al-Sufi, who says, in the preface to his work, that he has described the stars “as seen with my own eyes.” α Eridani is over 11 “cubits” from h Eridani instead of “4 cubits” as Al-Sufi says. This shows conclusively that the star seen by Al-Sufi was certainly not α Eridani. The interest of the identification is that Al-Sufi rated θ Eridani of the first magnitude, whereas it is now only 3rd magnitude! It was measured 3·06 at Harvard and estimated 3·4 by Stanley Williams, so that it has evidently diminished greatly in brightness since Al-Sufi’s time. There is an interesting paper on this subject by Dr. Anderson (the discoverer of Nova Aurigæ and Nova Persei) in Knowledge for July, 1893, in which he states that the “Last in the River,” according to the statements of Hipparchus and Ptolemy, did rise above their horizon at a certain time of the year, which α Eridani could not possibly have done. This seems sufficient to settle the question in favour of θ Eridani. Dr. Anderson says, “It is much to be regretted that Professor Schjellerup, the able and industrious translator of Sufi, has allowed this to escape his notice, and helped in the preface and note to his work to propagate the delusion that α Eridani is Ptolemy’s ‘Last in the River’”; and in this opinion I fully concur. Al-Sufi’s clear account places it beyond a doubt that the star known to Hipparchus, Ptolemy, Al-Sufi, and Ulugh Beigh as the “Last in the River” was θ Eridani. θ must have diminished greatly in brightness since Al-Sufi’s time, for in ranking it as 1st magnitude he placed it in a very select list. He only rated thirteen stars in the whole heavens as being of the 1st magnitude. These are: Arcturus, Vega, Capella, Aldebaran, Regulus, β Leonis, Fomalhaut, Rigel, θ Eridani, Sirius, Procyon, Canopus, and α Centauri. All these stars were actually seen by Al-Sufi, and described from his own observations. He does not mention α Eridani, as it was not visible from his station in Persia.

θ Eridani is a splendid double star (3·40, 4·49: 8″·38, 1902, Tebbutt). I found the components white and light yellow with 3-inch refractor in the Punjab. Dr. Gould thinks that one of the components is variable to some extent. This is interesting, considering the brilliancy of the star in Al-Sufi’s time. The brighter component was found to be a spectroscopic binary by Wright, so that on the whole the star is a most interesting object.

The small constellation Lepus, the Hare, lies south of Orion. Pliny calls it Dasypus, and Virgil Auritus. In ancient Egypt it was the symbol of vigilance, prudence, fear, solitude, and speed.431 It may perhaps represent the hare hunted by Orion; but some say it was placed in the sky to commemorate a terrible plague of hares which occurred in Sicily in ancient times.

A little north-west of the star μ Leporis is Hind’s “crimson star” (R.A. 4h 53m, S. 14° 57′, 1900) described by him as “of the most intense crimson, resembling a blood drop on the background of the sky; as regards depth of colour, no other star visible in these latitudes could be compared with it.” It is variable from about the 6th to the 8th magnitude, with a period of about 436 days from maximum to maximum.

The constellation Canis Major, the Great Dog, is remarkable for containing Sirius, the brightest star in the heavens. In the Greek mythology it was supposed to represent a dog given by Aurora to Cephalus as the swiftest of all dogs. Cephalus wished to match it against a fox which he thought surpassed all animals for speed. They both ran for so long a time, so the story goes, that Jupiter rewarded the dog by placing it among the stars. But probably the dog comes from Anubis, the dog-headed god of the ancient Egyptians. According to Brown, Theogirius (B.C. 544) refers to the constellation of the Dog.432 He thinks that Canis Major is probably “a reduplication” of Orion; Sirius and β Canis Majoris corresponding to α and γ Orionis; δ, 22, and ε Canis Majoris to the stars in Orion’s belt (δ, ε, and ζ Orionis); and η; and κ Canis Majoris with κ and β Orionis.433

The Arabic name of Sirius was al-schira, which might easily be corrupted into Sirius. The Hebrew name was Sihor. According to Plutarch, the Ethiopians paid regal honours to the Celestial Dog. The Romans used to sacrifice a dog in its honour at the fetes called Robigalia, which were held on the seventh day before the Calends of May, and nine days after the entry of the sun into Taurus. Pliny says, “Hoc tempus Varro determinat sole decimam partem Tauri obtinenti quod canis occidit, sidus per se vehemens,” etc.434

Owing to some remarks of Cicero, Horace, and Seneca, it has been supposed that in ancient times Sirius was of red colour. Seneca says, “Nec mirum est, si terra omnis generis et varia evaporatio est; quam in cœlo quoque non unus appareat color rerum, sed acrior sit Caniculæ rubor, Nartis remissior, Jovis nullus, in lucem puram nitore perducto.”435 It is now brilliantly white with a bluish tinge. But this change of colour is somewhat doubtful. The remarks of the ancient writers may possibly refer to its great brilliancy rather than its colour. Al-Sufi says nothing about its colour, and it was probably a white star in his time. If it were red in his day he would most probably have mentioned the fact, as he does in the case of several red stars. Brown, however, quotes the following from Ibn Alraqqa, an Arabian observer: —

“I recognize Sirius shining red, whilst the morning is becoming white.The night fading away, has risen and left him,The night is not afraid to lose him, since he follows her.”

Schjellerup thinks that it is very doubtful that Sirius was really red as seen by Hipparchus and Ptolemy. But in an exhaustive inquiry made by Dr. See on the supposed change of colour,436 he comes to the conclusion that Sirius was really red in ancient times. Seneca states distinctly that it was redder than Mars (see extract above), and other ancient writers refer to its red colour. It has been generally supposed that the Arabian astronomer Alfraganus, in his translation of Ptolemy’s Almagest, refers to only five red stars observed by Ptolemy, namely, Arcturus, Aldebaran, Betelgeuse, Antares, and Pollux. But Dr. See shows that this idea is due to a mistranslation of Alfraganus by Plato Tibertinus in 1537, and that Ptolemy did not speak of “five red stars,” but five nebulous stars, as stated by Christmann and Golius. Ptolemy described Sirius as ὑπόκιρρος, “fiery red,” the same word used with reference to the other stars mentioned above. The change of colour, if any, probably took place before Al-Sufi’s time.