Zodiac

The zodiac is a special area in the sky that stretches about 8° north and south of the path the Sun appears to follow over the year, called the ecliptic. This path is important because the Moon and bright planets also move through this area as they orbit the Sun.

The zodiac is divided into 12 equal parts, called "signs", each covering 30° of the sky. These signs match up closely with 12 groups of stars called constellations, which have names like Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius, and Pisces.

People have used the zodiac for thousands of years to help tell the time of year. Ancient Babylonian astronomers created this system during the 1st millennium BC, and it later spread to Greek astronomy and other cultures. Even today, scientists still use a version of this system to track objects in our Solar System.

Name

The word zodiac comes from an old Latin word, which itself comes from Ancient Greek. It means "of or relating to little animals." This name fits because many of the twelve zodiac signs are animals or creatures from myths.

In English, the word zodiac can also refer to a twelve-year cycle that comes from East Asian traditions, known as the Chinese zodiac. This cycle also uses animals to represent each year and people often use it to talk about personality and life events.

Main articles: Chinese zodiac, Earthly Branches

Usage

The zodiac has been used since ancient times, starting with the Roman era. It was built on ideas from Hellenistic astronomy and Babylonian astronomy. A famous book called the Almagest by Ptolemy describes how the zodiac was made.

Today, the zodiac is mostly linked to horoscopic astrology. It also means the area of the sky where planets travel, about 8 degrees above and below the path the Sun appears to take. For example, the Moon’s path has a smaller zodiac band of 5 degrees above and below this same line.

History

Further information: Former constellation

Early history

Long ago, around the 14th century BC, people in Egypt made a list of special stars called decans. These appeared in ancient tombs and temples. Later, around the first half of the 1st millennium BC, people in Babylon divided the path the Sun follows in the sky into 12 equal parts. They called these parts "signs," and each one covered 30 degrees of the sky. This was one of the first ways to measure positions in the sky.

Babylonian astronomers used stars as markers to find the positions of planets. They measured where planets were by comparing them to these marker stars close to the Sun's path. They also made special tables to predict where planets would be in the future.

Hebrew astronomy and astrology

Some stories from ancient Hebrew writings mention ideas that might connect to the 12 signs of the zodiac. For example, some writers thought the special creatures described in these writings matched the signs of the zodiac, like a lion for Leo and a bull for Taurus.

Hellenistic and Roman era

The ideas about the zodiac from Babylon spread to Greece and Rome. Greek writers like Ptolemy wrote books explaining how the signs of the zodiac worked. Ptolemy helped create a system where the zodiac was linked to the seasons, like spring and summer, instead of just the stars.

Hindu zodiac

The zodiac also reached ancient India, where it was changed to match their own star system. Even though the names and symbols were different, the basic ideas stayed the same. For example, one sign in India was called "dhanu," which means "bow," just like the sign Sagittarius, which means "archer."

Middle Ages

During the Middle Ages, many people in Europe and the Middle East were interested in the zodiac. Books were written about the stars, and some churches even had beautiful windows showing the zodiac signs. Astrologers used special tools to figure out what the stars might mean for people's lives.

Medieval Islamic era

In the time of ancient Islam, many people believed the stars could tell the future. They used the zodiac to help decide important events, like when to start building a city. Some leaders even used astrology to pick lucky dates. However, not everyone agreed with this, and some religious leaders thought it was wrong to try to predict the future.

Early modern

Later on, sailors used the zodiac to help them navigate the seas. They had special books that told them where the Sun and Moon were in the sky. Kings and artists also loved the zodiac, and it appeared on coins and in paintings.

Twelve signs

Main article: Astrological sign

The zodiac is divided into twelve equal parts, called signs. Each sign covers 30 degrees of the sky. These signs have special names and symbols from many cultures. A common way to remember them is through a rhyme:

The ram, the bull, the heavenly twins,
And next the crab, the lion shines,
    The virgin and the scales,
The scorpion, archer, and the goat,
The man who holds the watering-pot,
    And fish with glittering scales.

The Sun moves through each sign for about the same amount of time, but the exact days can change a little each year. This is because Earth's path around the Sun is not a perfect circle.

Constellations

These two maps of the constellations, made two centuries apart, both show the zodiac constellations along a curved line representing the ecliptic.

In tropical astrology, the zodiacal signs are different from the constellations they are named after. This is because, over time, these signs have moved slightly due to a change in Earth's tilt. Also, the actual space the Sun takes to pass through each constellation is not the same — for example, Virgo takes up five times more space than Scorpius. The zodiacal signs are an idea created from the constellations, and each sign takes up exactly one-twelfth of the full circle, but the time the Sun spends in each sign changes a little because of the shape of Earth's orbit.

Sidereal astrology tries to match the zodiac signs more closely to the real constellations, but it needs to be adjusted from time to time to stay correct.

The path of the Sun crosses through 13 constellations from ancient lists. Besides the twelve constellations that give their names to the zodiac signs, the path also goes through Ophiuchus, which sits between Scorpius and Sagittarius. Sometimes people mistakenly think this means the list of traditional signs has changed, but this is not true.

Some other constellations are sometimes thought of as part of the zodiac too, and planets can pass through up to 25 different constellations. Ancient lists included Orion, Perseus, Auriga, and Andromeda. Today, we know planets can also go through Crater, Sextans, Cetus, Pegasus, Corvus, Hydra, Orion, and Scutum. Very rarely, Venus might pass through Aquila, Canis Minor, Auriga, and Serpens.

Other constellations have stories connected to the zodiac ones. For example, Piscis Austrinus, The Southern Fish, is linked to Aquarius. In old drawings, it seems to catch the water poured from Aquarius' jug. Aquila, The Eagle, might have been linked to the zodiac because of its bright star, Altair. Long ago, Hydra marked a special line in the sky and was connected to Leo, which is often shown standing on the snake on the Dendera zodiac.

Precession of the equinoxes

Further information: Axial precession, Epoch (astronomy), Sidereal and tropical astrology, Astrological age, and Ayanamsa

The zodiac system began in Babylonia about 2,500 years ago. It was created during a time called the "Age of Aries." Back then, people did not know about the precession of the equinoxes, a slow wobble of Earth's axis.

Today, the zodiac can be used in two ways: one where the signs stay fixed to the stars (sidereal), and one where the signs are tied to the Sun's position at the March equinox (tropical). Western astrology uses the tropical way, while Hindu astrology uses the sidereal way. Because of the precession of the equinoxes, these two systems slowly move apart by about 1.4 degrees every century.

In Western astrology, the sign Aries is now actually found in the constellation Pisces, which is why we hear about the “Age of Pisces.” The sidereal system corrects for this shift using something called the ayanamsa. The idea of precession was discovered by Hipparchus around 130 BC. Later, Ptolemy wrote about it in his book, the Almagest. He explained that Greek astronomers started their zodiac at the point where the Sun is during the March equinox, calling this the first degree of Aries. This is known as the tropical zodiac.

In modern astronomy

The zodiac is an area of space that stretches about 8° to the north and south of the path the Sun appears to follow in the sky over a year, called the ecliptic. This area includes the paths of the Moon and the main planets. Because most planets orbit close to Earth's orbital plane, this area is narrow.

Astronomers once used the zodiac to measure positions in the sky, starting from a point called the "first point of Aries." The zodiac is divided into twelve equal parts, or signs, each covering 30° of this path. Today, astronomers usually use a different system based on Earth's axis, but the zodiac still helps us understand where planets and the Moon move. The zodiac also gives its name to a faint glow in the night sky called the zodiacal light, caused by sunlight reflecting off tiny particles between the planets.

Unicode characters

In Unicode, the symbols for the zodiac signs are found in a special area called "Miscellaneous Symbols". You can make these symbols look like regular text by adding a special code U+FE0E, or make them look like colorful pictures (emojis) by adding U+FE0F.