That sign so often dubbed the Goat,
Yet with a fish’s tail.”
Capricorn has very few bright stars. There are two in his goat’s head, of which the brightest, Alpha, is a beautiful naked-eye double, and there are two in his fish’s tail. These three figures—a Scorpion, Centaur-archer, and Capricorn—are carved on old Babylonian boundary-stones belonging to the second millennium b.c.
Following these is Aquarius, the Water-carrier, his shoulder marked by the star β, and his pot by four stars (α, γ, ζ, η), from which fall splashes and streams of faint stars, aptly representing the water which he is pouring out. He is a familiar figure to those who have lived in some countries of the East where water is all carried by hand.
THE ARCHER
From a Babylonian Boundary Stone now in the British Museum.
This is a very watery part of the heavens, for the zodiacal pair of Fishes follows the Water-carrier (their only bright star in the northern hemisphere), and there is also a solitary Fish, Piscis Australis, swimming in the water poured out; while a little further east is the great Sea-Monster, which belongs to the northern group of Perseus and Andromeda and her parents Cepheus and Cassiopeia. Only the head of Cetus, the Sea-Monster, is in the northern hemisphere, but that contains its brightest star. Between the dim Sea-Monster and the bright Orion flows the winding River Eridanus: it rises near Orion’s foot, and now ends very far south in the bright star Achernar; but this star was not visible to Ptolemy when he drew up his star-catalogue in Alexandria, and the original Achernar, or Last-of-the-River, seems to have been what we now call Theta Eridani, which was much brighter some centuries ago than it is now. Al-Sufi, an Arab writer of the tenth century a.d., calls it a star of first magnitude.
To complete our survey of the constellations south of the equator we must add the tip of the Eagle’s wing, the legs of the Unicorn, and part of Ophiuchus with the Serpent he is strangling as he treads the Scorpion under foot (a gallant hero, to contend with both these enemies at once).
It is worth noting that just as the three stars of Orion’s belt mark the celestial equator in one part of the sky, so the three bright stars of the Eagle mark it in the opposite part (Altair, with β and γ on either side); but they are just north of it, and Orion’s belt is just south. As it is often interesting to know where the ecliptic lies, we may point out that the following southern stars lie near it: Spica, α Librae, Antares, α and β Capricorni (and in the north the Pleiades, Aldebaran, Regulus). It is also convenient to remember the positions of a few constellations as a guide to right ascension. Thus, Achernar is in the Ist hour, Canopus and Sirius are in the VIth, the Cross and Corvus in the XIIth, and the Bow of Sagittarius is in the XVIIIth.[4]