Zodiac

The zodiac is a belt-shaped region of the sky that extends approximately 8° north and south (as measured in celestial latitude) of the ecliptic, which is the apparent path of the Sun across the celestial sphere over the course of the year. The orbital paths of the Moon and major planets are within the belt of the zodiac. In Western astrology, and formerly astronomy, the zodiac is divided into the following twelve signs: Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius, and Pisces. Each occupies 30° of celestial longitude and roughly correspond to the astronomical constellations with the same name. These astrological signs form a celestial coordinate system, or more specifically an ecliptic coordinate system, which takes the ecliptic as the origin of latitude and the Sun's position at vernal equinox as the origin of longitude. This division of the ecliptic into zodiacal signs originated with Babylonian astronomy during the 1st millennium BC. Babylonian astronomers divided the ecliptic into 12 equal "signs". Due to the precession of the equinoxes, the time of year the Sun is in a given constellation has changed since Babylonian times, and the point of March equinox has moved from Aries into Pisces. The zodiac was communicated into Greek astronomy by the 2nd century BC, and from there into the Hindu zodiac. In modern astronomy, the ecliptic coordinate system is still used for tracking Solar System objects. The English word derives from zōdiacus, the Latinized form of the Ancient Greek zōdiakòs kýklos (ζῳδιακός κύκλος), meaning "cycle or circle of little animals". Zōdion (ζῴδιον) is the diminutive of zōon (ζῷον, "animal"). The name reflects the prominence of animals (and mythological hybrids) among the twelve signs. The zodiac was in use by the Roman era, based on concepts inherited by Hellenistic astronomy from Babylonian astronomy of the Chaldean period (mid-1st millennium BC), which, in turn, derived from an earlier system of lists of stars along the ecliptic.