What Is the Zodiac?
The Zodiac is a group of constellations that encircle the path traveled by the planets as we watch from the earth. The word “zodiac” is Greek for “circle of animals.” Ancient people imagined these star groups to be figures of animals or people. The name is motivated by the fact that half of the signs of the classical Greek zodiac are represented as animals (besides two mythological hybrids).
The signs of the zodiac are: Aries (the Ram), Taurus (the Bull), Gemini (the Twins), Cancer (the Crab), Leo (the Lion), Virgo (the Virgin), Libra (the Scale), Scorpio (the Scorpion), Sagittarius (the Archer), Capricorn (the Goat), Aquarius (the Water Bearer), and Pisces (the Fish). A kind of fortune telling based on the zodiac is called astrology.
Essentially, the zodiac is a celestial coordinate system, or more specifically an ecliptic coordinate system, which takes the ecliptic as the origin of latitude, and the position of the Sun at vernal equinox as the origin of longitude. Although the zodiac remains the basis of the ecliptic coordinate system in use in astronomy besides the equatorial one, the term and the names of the twelve signs are today mostly associated with horoscopic astrology.
The term “zodiac” may also refer to the region of the celestial sphere encompassing the paths of the planets corresponding to the band of about eight arc degrees above and below the ecliptic. The zodiac of a given planet is the band that contains the path of that particular body; e.g., the “zodiac of the Moon” is the band of five degrees above and below the ecliptic. By extension, the “zodiac of the comets” may refer to the band encompassing most short-period comets.