The zodiac is one of the most well-known facets of astrology. It comprises 12 constellations (and star signs) through which the sun appears to pass (the ecliptic path), dividing the sky into 12 equal sections. These constellations are used in astrology and horoscopes to help predict future outcomes and interpret human behaviour and personality traits. The star signs, which we have all heard of and are familiar with, are Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius, and Pisces.

However, there is another star sign, a 13th star sign, which far fewer people have heard of and know, one that was discarded many, many years ago. The constellation Ophiuchus crosses the ecliptic between November 29 and December 17, nestled between Scorpio and Sagittarius. Known as the ‘Serpent Bearer,’ debate has raged within the astrological community over whether Ophiuchus should be added to the zodiac.

It was Babylonian scholars who developed the first zodiac system approximately 3,000 years ago. They divided the sky into 12 equal parts, which fitted nicely with their 12-month calendar system.

While this still forms the basis of the zodiac we know today, it is worth noting that the position of the stars documented by the ancient Babylonians has changed over the centuries, due to the wobble of the earth’s axis and the movement of the solar system and stars.

While the Babylonians recognised Ophiuchus as a constellation, several factors are believed to have led to its omission from the zodiac. Ophiuchus only partially crosses the ecliptic, in contrast to the other zodiac constellations, which are largely contained within the ecliptic. Adding this constellation to the zodiac would also disrupt the equal division of the ecliptic into 12 equal parts of 30 degrees.

The number 12 also held special importance and symbolic significance in many ancient civilisations. Apart from the 12 lunar months aligning with the zodiac calendar, the number represents a full circle, as well as the separation of day and night into 12 hours.

Over millennia, the 12-sign system has become entrenched in Western philosophy. Introducing Ophiuchus as a thirteenth star sign would upheave this system as we know it, affecting astrological interpretations and practices that have been in use for thousands of years.

However, the argument to include the thirteenth star sign is equally compelling. The ecliptic does indeed pass through the Ophiuchus constellation, and it can be argued that the Babylonians’ decision to exclude it for their simplified 12-sign system came at the expense of astronomical accuracy. Welcoming Ophiuchus back into the zodiac fold would mark a return to the original astronomical observations. It would create a more complete astrological picture and be a step towards a more accurate system.

The debate over whether to adhere to the original calendar, drawn up approximately 3,000 years ago, or to include Ophiuchus in the zodiac, is one that is sure to continue within the astrological community for a long time to come.