Al Thurayya

Al Thurayya is the third lunar mansion, spanning roughly 25 to 38 degrees of the ecliptic across the Aries-Taurus border. Its name is the Arabic for the Pleiades, the bright star cluster it contains, the same asterism the Vedic tradition counts as the nakshatra Krittika, a rare point where the two lunar-mansion systems name the same visible stars. In the manazil tradition its planetary ruler is Jupiter, and its traditional talismanic virtue is favour and harvest, promising increase and the good will of others. The magical property, like that of every mansion, was fixed in the Arabic manazil literature and carried into Latin through the Picatrix and Agrippa for the timing of talismans. These are the conventions of that tradition; the underlying cluster is the Pleiades, prominent in the calendars of many ancient peoples.

Because Al Thurayya shares its underlying stars with the nakshatra Krittika, the two systems agree exactly at this one point in the circle even though their overall degree divisions, twenty-eight equal stations against twenty-seven, drift apart everywhere else; it is one of the clearest concrete illustrations of the deep kinship between the manazil and the nakshatras that this atlas's entry on the first mansion discusses more fully. The Pleiades' heliacal rising was also a marker in the pre-Islamic Arabian anwa' calendar independent of its later role in this talismanic scheme, used to anticipate seasonal weather changes across the Arabian peninsula in a practical tradition that predates and stands apart from the mansion magic recorded by the Picatrix and Agrippa.

Where the zodiac cuts the ecliptic into twelve, the manazil cut it into twenty eight, and the number comes from the Moon's daily motion rather than from any figure in the sky. Each mansion is exactly twelve degrees fifty one minutes wide, one twenty eighth of three hundred and sixty. Al Thurayya is the third of them, running from 25 degrees 43 minutes of Aries to 8 degrees 34 minutes of Taurus. The Moon's mean daily motion of about thirteen degrees eleven minutes is slightly more than one mansion, so it completes the circuit of all twenty eight in the sidereal month of twenty seven and a third days, not in the twenty nine and a half of the synodic month the phases follow.

The Arabic manazil al qamar reached Latin Europe through translation in the twelfth and thirteenth centuries, and the magical use of the mansions travelled with the astronomical scheme rather than after it. Agrippa set out all twenty eight with their degrees and their operations in the second book of the Three Books of Occult Philosophy, and that chapter, not any Arabic original, is where almost every later English language list comes from. Al Thurayya is a transliteration, and the spellings vary widely between sources.

There is a problem in those degrees that the printed lists rarely flag. The mansions are named for star groups, but the boundaries above are measured in the tropical zodiac, anchored to the equinox, which drifts against the stars at about one degree every seventy two years. The Arabic scheme was fixed to the stars themselves. Something close to twenty degrees of precession has accumulated since the medieval transmission, so a mansion's tropical degrees no longer contain the stars it is named after. Both readings are in circulation and neither is a misprint.