In astronomy and astrology, a belt around the heavens extending 9 degrees on either side of the ecliptic, the plane of the earth's orbit and of the sun's apparent annual path. The orbits of the moon and of the principal planets (except Pluto) also lie entirely within the zodiac. The 12 astrological signs of the zodiac are each considered to occupy 1/12 (or 30 degrees) of its great circle. The Babylonian and Greek signs of the zodiac were introduced into Egypt in the Greco-Roman Period.