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 east
And, slow ascending one by one,
The kindling constellations shone
Begirt with many a blazing star
Stood the great giant Al-gebar
Orion, hunter of the beast!
His sword hung gleaming at his side
And on his arm, the lion’s hide—
Scattered across the midnight air
The 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.[430] 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.[431] 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.[432] 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.