I think it is not any particular star, but a star near the location of the equinox which would be changed over time to another star. Someone would have to know which star it is in the sky and could use it to determine east.... The Egyptians appear to be the origin of this concept "Star of the Orient" and a North African trader might be using folk knowlege based on that old Egyption tradition. Look in (forgive me) astrology and see what you can find. The following is from some astrology webpages...... "The birthplace of the Egyptian Messiah [Horus] at the Vernal Equinox was figured in Apt, or Apta, the corner. But Apta also means the Crib and the Manger, therefore the child born in the Apta was supposed to be born in the Crib, and this Apta, as Crib, is the hieroglyphic sign of the birthplace of the Sun.This point was indicated by the intersection of the Colure of the Equinox with the Equator, and as it passed from sign to sign, the corresponding star of the Orient (or of the East) served to mark its position. According to their way of registering a knowledge of the beginnings, the Egyptians were well acquainted with the equatorial regions, which they designated "Apta" , the uppermost point, the mount, or literally the "horn-point" of the earth. This was afterwards reproduced at the highest point above, when the primeval birth land was repeated as the land of rebirth for spirits in heaven"