What are the twelve zodiac signs?

Quels sont les douze signes du zodiaque ?

The Earth is a roughly spherical celestial body, and when we gaze at the sky, it appears as a spherical expanse known as the celestial sphere, with stars twinkling like gems embedded within it. Over 1,000 years BC, the ancient Babylonians sought to understand fortunes and navigation by connecting these celestial gems into patterns, ultimately dividing the sky into more than thirty regions, which served as the prototypes for constellations.

In 1928, the International Astronomical Union redefined these boundaries, creating 88 distinct constellations, among which are the twelve zodiac signs. Interestingly, while we typically refer to twelve zodiac constellations, there is actually a thirteenth one known as Ophiuchus.

The Ecliptic and the Zodiac

The term “Twelve Zodiac Constellations” derives from the concept of the “ecliptic.” From our perspective on Earth, the path traced by the Sun as it orbits around us forms a plane called the ecliptic. The twelve zodiac signs are located along this celestial sphere, directly opposite the ecliptic. As we observe from Earth, the Sun appears to move through each of these constellations over the course of the year, which is why we refer to them as the “Twelve Zodiac Signs” in astrology.

Each month corresponds to a different zodiac sign based on the Sun’s position. For instance, during the vernal equinox, the Sun is in Aries, meaning those born between March 21 and April 19 are considered Aries. However, Aries is not visible in the night sky at this time, as it is obscured by the Sun. When does Aries fully emerge? Six months later, around September 21. Due to the precession of the equinoxes, the Sun is currently in Pisces during the vernal equinox, yet astrologers still classify late March birthdays as Aries.

Star Map of Aries

In this star map, the area highlighted by the yellow circle depicts Aries.

Zodiac Signs: A Deeper Understanding

The twelve zodiac signs are a derived concept from the zodiac, with their nomenclature rooted in Arabic astrology. The zodiac encompasses the Sun’s trajectory on the celestial sphere, passing through 13 of the 88 constellations. These 13 constellations are collectively known as the zodiac constellations. The zodiac is divided into 12 equal sections called “houses,” each named after its corresponding zodiac constellation. Notably, each of the twelve zodiac constellations, excluding Ophiuchus, has a corresponding house, thereby collectively forming the “zodiac constellations.”

Historical Context and Source

The concept of the twelve zodiac signs has its origins in Arabic astrology. In northern Arabia, water signs share both benefic and malefic stars with fire signs, while in southern Arabia, fire signs exchange stars with earth, air, and water signs. Uniquely, Gemini and Leo interchange malefic stars, and Sagittarius and Aquarius share benefic stars, although the reasons for these exchanges remain unclear.

Over 1,000 years BC, the ancient Babylonians established the initial connections among the stars, dividing the sky into more than 30 regions, which laid the groundwork for modern constellations. In 1928, the International Astronomical Union delineated the boundaries of the 88 constellations, identifying 13 zodiacal constellations through which the ecliptic passes: Pisces, Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Ophiuchus, Sagittarius, Capricornus, and Aquarius. The sizes of these zodiacal constellations vary significantly; Virgo is the largest, while Scorpio is the smallest, measuring less than one-third of Virgo’s size.

The twelve zodiac constellations are formed by equally dividing the ecliptic. Although they are named after twelve zodiac signs (excluding Ophiuchus), some confusion arises due to the similar terminology of “constellation” and “zodiac sign.” For example, astrology attributes the label “Aries” to individuals born on the spring equinox (March 21), which aligns with the Aries constellation. However, the spring equinox has shifted over 30 degrees westward due to the precession of the equinoxes, meaning it now falls in Pisces instead of Aries. Ultimately, while Ophiuchus is one of the zodiac constellations, it is not classified among the twelve zodiac signs.