Heavenly Writings: The Babylonian Origins of Astrology

Over three millennia ago, Mesopotamian scholar-scribes recorded the path of the heavenly bodies across the sky to decipher omens from the gods, laying the foundation for what would become Hellenistic astrology.

Published Categorized as History
The list gives each constellation, the number of stars and the distance information to the next constellation in ells. Special exhibition "Beyond the Horizon - Space and Knowledge in the Old World cultures" at the Pergamon Museum (22.06 -. 30.09.2012)
Star list with distance information, Uruk (Iraq), 320-150 BC

Sky and Earth both produce portents; though appearing separately, they are not separate, for sky and earth are joined.

– Babylonian Diviner’s Manual

Almost 3,000 years ago, in what is now Iraq, soothsayer-scribes stood atop stepped ziggurats, gazing up at the sky. Known as ummanu, these learned men would record what they saw on wet lumps of clay, using a reed stylus to cut cuneiform characters into the clay. But what were they looking for, and what bearing did the heavens have over human affairs in ancient Mesopotamia? In the answer to these questions lies the very roots of astrology.

It was the Sumerians who, in addition to creating the cuneiform writing system, first identified and named the constellations. By 1700 B.C., observing the sky was one of the primary ways in which Babylonian ummanu deciphered omens from the gods, alongside examining the livers of sacrificed animals. But, in contrast to variations in sheep viscera, astronomical phenomena were regular. As avid list makers, the Babylonians discovered that, with the right data, anything from the motion of Venus to the timing of eclipses could be predicted. Before the invention of trigonometry or even the concept of orbital planetary movement, the Babylonians managed to develop mathematical functions that could effectively predict the motion of the heavenly bodies. They penned tablet after tablet of astrological compendia and developed new and increasingly scientific methods for reading the heavenly writings of their gods.

By the last century B.C., the great cities that had made Mesopotamia a center of political, spiritual, and scientific innovation for millennia had fallen into decline. Foreign domination, first by the Persians and then the Alexandrian Greeks, meant that the wedge-shaped cuneiform script fell out of use in favor of Aramaic and Greek. State support for astrology decreased as political power shifted, and the Hellenistic world expanded to reach from the shores of the Adriatic to the Indus River Valley. But even as the wealth and power of Mesopotamia dwindled, its intellectual accomplishments were carried far beyond its borders, turning a local phenomenon into one of the cornerstones of the Hellenistic world.

The Babylonian Worldview

In many ways, Babylonian astrology was a byproduct of ancient Mesopotamian religious beliefs. Prosperous and well-organized cities in the fertile areas surrounding the Euphrates and Tigris rivers were ruled by kings, who at times extended their rule over greater or lesser areas in the region in history’s first empires. Each city had its principal patron god among the Mesopotamian pantheon, often featured in the epics that scribes recorded on cuneiform tablets.

In addition to their earthly duties, Babylonian kings were considered representatives of the gods on Earth. A king’s responsibility to maintain a balance between his kingdom and the heavens was symbolized by his tending to a sacred tree. Kings would, in the governance of their kingdoms, err from time to time and provoke the wrath of the gods. Fortunately, the gods would not seek revenge without first issuing a warning, whether through portents or dreams.

Eclipses were particularly ill omens, and Mesopotamian sources record instances of installing a dummy king during eclipses to avoid harm befalling the real king. Other astrological portents would grow in importance as the field developed over almost two millennia. The twin roles of the ummanu, that class of scholar-soothsayers, was to school the king in these portents, as well as perform rituals to restore the king’s purity. Their knowledge was said to have come to mankind from apkallu, hybrid half-animal half-human beings that lived on Earth in times past.

Black and white crop of full engraving plate scan - from Plate 5 of the work "A second series of the monuments of Nineveh: including bas-reliefs from the Palace of Sennacherib and bronzes from the ruins of Nimroud ; from drawings made on the spot, during a second expedition to Assyria" (AH Layard)
Bas-relief at an entrance to a small temple in Nimroud depicting battle of Marduk vs Tiamat – story from Enūma Eliš

Many contemporary scholars believe that Babylonian astrology as such arose from the combination of star worship and the observations of celestial events as necessitated by calendar-making. In the Enuma Elish, the Babylonian creation epic, the gods created the heavens to mark the passage of time. Each luminary—the Sun, the Moon, and the five visible planets was each linked to certain gods. Jupiter, for example, represented Marduk, the head Babylonian deity and the protagonist of the Enuma Elish, while Venus represented Ishtar, the goddess of love, battle, fertility, and storms. As omens, each planet was eventually associated with the benefic or malefic nature that would translate into Hellenistic astrological practices.

Astrology in Babylon

The first form of astrology practiced in Mesopotamia was what by modern standards would be called “mundane” astrology. It did not deal in the fates or fortunes of individuals (apart from the king) and instead focused on the welfare of the city or kingdom as a whole. From their observations of the sky, the ummanu would record celestial phenomena on clay tablets that would be delivered to the king with an interpretation. These interpretations could be drawn from previous instances in which a given celestial event occurred, or via association. The king could then, in turn, send queries in return to the ummanu, an early but recognizable form of the relationship between astrologer and client. Predictions might relate to significant meteorological events, warfare, crops, and famine, or any other aspect of the state’s well-being, but there was no assumption of any cause and effect relationship between astrological occurrences and earthly matters. The Babylonians also practiced a form of astral medicine, with varying remedies based on the date and zodiac sign.

The knowledge we have of astrology in ancient Mesopotamia comes largely from tablets penned by the ummanu. The earliest sources were compendia listing the rising and setting times of heavenly bodies, star charts, or omen texts. The Enuma Anu Enlil is the oldest known astrological compendium, listing over 7,000 omens over the course of 70 clay tablets. The omens were likely first written down during the Old Babylonian period and refer to an even older oral tradition, but the copy that has survived is from the Assyrian king Ashurbanipal’s library at Niveh and was likely written in the 7th century B.C.

Cuneiform tablet; Clay-Tablets-Inscribed
Cuneiform tablet: commentary on Enuma Anu Enlil, tablet 5, ca. late 1st millennium B.C.

It was around this time that the Babylonians developed a number of key astrological innovations. First, astronomers began to record the daily position of the visible planets in early ephemerides known as Astronomical Diaries. Eventually, linear functions of time were developed to measure planetary velocity. These mathematical processes, along with the immense amount of data that Babylonian astronomers had amassed, allowed for effective predictions of celestial phenomena. This meant that, instead of making observations just before or slightly after an event, astrologers could predict planetary positions in both the past and the future, allowing them to forecast eclipses and other important omens and—as we will soon see—calculate the earliest horoscopes.

By 400 B.C., the Babylonians had also identified the ecliptic as the path of the Sun, thus delineating the 12 constellations of the zodiac still in use today. As fixed stars, known as “normal” stars, played such a vital role in the Babylonian calendar, the Babylonian zodiac was fixed sidereally (in relation to stars) rather than tropically (in relation to the equinoxes and solstices). The passing of the four seasons coincided with the rising of the brightest stars in the fixed signs of Taurus, Leo, Scorpio and Aquarius. While each constellation of the zodiac is a different size, the Babylonians eventually divided the sky into twelve 30° arcs and used each segment to identify the position of a planet at any given time. They also grouped the zodiac signs into four groups of three based on a 120° aspect, an early form of triplicities, and established “secret houses” for each planet, the origin of Hellenistic exaltations.

Once these developments had occurred, texts began to appear describing planetary positions with signs of the zodiac. With these come the very first horoscopes. Twenty-eight such texts, written between 400 and 100 B.C., survive to the current day. These texts include no version of a birth chart, a relatively modern invention, but instead consist of the client’s name, a list of planetary positions at the native’s date of birth, and little to no interpretation. The appearance of Greek names among the clients reflected the growth of foreign influence within Mesopotamia. By 125 B.C., Parthinian domination in the region meant a virtual end to Mesopotamian arts and sciences, but astrology itself would survive to flourish in other lands.

The Legacy of Babylonian Astrology

The reason behind the shift in Babylonian astrology from mundane to natal is unclear. However, it is likely that the splintering of political power in the region and foreign invasion meant less state support for astrology, such that astrologers may have begun to practice for wealthy private clients. Regardless, the practice of rulers referring to astrologers to decipher celestial omens remained a popular practice through the Hellenic and Roman eras while the practice of natal astrology continues to this day.

How did the unique Mesopotamian system for deciphering celestial omens become so influential? The Jews learned of astrological and religious practices of the region during their Babylonian captivity (587-539 B.C.), eventually recording them in their scriptures. In 290 B.C., a Babylonian scholar and astrologer reportedly founded a school on the Greek island of Kos, and throughout the Hellenic world astrologers were often known as “Chaldeans”, a term referring to Babylonians. But it was in India and Ptolemic Egypt that Babylonian astrology would find the most fertile ground. Babylonian astrological practices reached Egypt as early as 500 B.C., where they merged with indigenous astrological practices and star lore. By the time of Ptolemy, the Egyptian city of Alexandria would be considered the center of Hellenistic astrology, a syncretic proto-science boasting a blend of Mesopotamian, Egyptian and Greek influences. Meanwhile, the first 49 tablets of the Enuma Anu Enlil reached northern India by the 4th century B.C., thanks to the Persians, and astrological materials soon began appearing in Sanskrit, including the 1st century A.D. text Garga Samhita. Lastly, in the addition to the impact Babylonian astrology would have on everything from the fates of Greek merchants to the succession of Roman emperors, researcher Ulla KochWestenholz identified in the practice the early elements of what would become a science. First, for the ummanu of Mesopotamia, the heavenly bodies operated by logical rules. These rules could be deciphered through the collection of data over time in early ephemerides. Lastly, the collection of data and consistent observation lead to the first “if x, then y” statements in the form of omen statements. In this way, the words and writings of Babylonian astrologers, gazing at the skies from atop their ziggurats some three millennia ago, still echo in our world today.


  • Astrology: A History by Dr. Peter Whitfield
  • The Fated Sky by Benson Bobrick
  • Babylonian Astrology, Wikipedia
  • Babylonian Horoscopes By Francesca Rochberg
  • Study of Babylonian Observations sign boundaries by Gray and Steele
  • Studies on Babylonian Goal-Year Astronomy Part I by Gray and Steele
  • Babylonian Goal-Year Astronomy by Jennifer Gray
  • Hellenistic Astrology – The Study of Fate and Fortune by Chris Brennan
  • History of Horoscopic Astrology by James Holden

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