Babylonian astronomy was the study or recording of celestial objects during early history Mesopotamia.

These records can be found on Sumerian clay tablets, inscribed in cuneiform, dated approximately to 3500–3200 BC.

In conjunction with their mythology, the Sumerians developed a form of astronomy/astrology that had an influence on Babylonian culture. Therein Planetary gods played an important role.

Babylonian astronomy seemed to have focused on a select group of stars and constellations known as Ziqpu stars.

These constellations may have been collected from various earlier sources. The earliest catalog, Three Stars Each, mentions stars of the Akkadian Empire, of Amurru, of Elam and others.

A numbering system based on sixty was used, a sexagesimal system. This system simplified the calculating and recording of unusually great and small numbers. The modern practices of dividing a circle into 360 degrees, of 60 minutes each, began with the Sumerians.

During the 8th and 7th centuries BC, Babylonian astronomers developed a new empirical approach to astronomy. They began studying and recording their belief system and philosophies dealing with an ideal nature of the universe and began employing an internal logic within their predictive planetary systems.

This was an important contribution to astronomy and the philosophy of science, and some modern scholars have thus referred to this novel approach as the first scientific revolution.

This approach to astronomy was adopted and further developed in Greek and Hellenistic astrology. Classical Greek and Latin sources frequently use the term Chaldeans for the astronomers of Mesopotamia, who were considered as priest-scribes specializing in astrology and other forms of divination.

Only fragments of Babylonian astronomy have survived, consisting largely of contemporary clay tablets containing astronomical diaries, ephemerides, and procedure texts, hence current knowledge of Babylonian planetary theory is in a fragmentary state.

Nevertheless, the surviving fragments show that Babylonian astronomy was the first “successful attempt at giving a refined mathematical description of astronomical phenomenaand thatall subsequent varieties of scientific astronomy, in the Hellenistic world, in India, in Islam, and in the West … depend upon Babylonian astronomy in decisive and fundamental ways.

The origins of Western astronomy can be found in Mesopotamia, and all Western efforts in the exact sciences are descendants in a direct line from the work of the late Babylonian astronomers.

Modern knowledge of Sumerian astronomy is indirect, via the earliest Babylonian star catalogs dating from about 1200 BC. The fact that many star names appear in Sumerian suggests a continuity reaching into the Early Bronze Age.

Old Babylonian astronomy

Old” Babylonian astronomy was practiced during and after the First Babylonian Dynasty (ca. 1830 BC) and before the Neo-Babylonian Empire (ca. 626 BC).

The Babylonians were the first to recognize that astronomical phenomena are periodic and apply mathematics to their predictions.

Tablets dating back to the Old Babylonian period document the application of mathematics to the variation in the length of daylight over a solar year.

Centuries of Babylonian observations of celestial phenomena were recorded in the series of cuneiform tablets known as the Enûma Anu Enlil—the oldest significant astronomical text that we possess is Tablet 63 of the Enûma Anu Enlil, the Venus tablet of Ammisaduqa, which lists the first and last visible risings of Venus over a period of about 21 years. It is the earliest evidence that planetary phenomena were recognized as periodic.

An object labeled the ivory prism was recovered from the ruins of Nineveh. First presumed to be describing rules to a game, its use was later deciphered to be a unit converter for calculating the movement of celestial bodies and constellations.

Babylonian astronomers developed zodiacal signs. They are made up of the division of the sky into three sets of thirty degrees and the constellations that inhabit each sector.

The MUL.APIN contains catalogs of stars and constellations as well as schemes for predicting heliacal risings and settings of the planets, and lengths of daylight as measured by a water clock, gnomon, shadows, and intercalations.

The Babylonian GU text arranges stars in ‘strings‘ that lie along declination circles and thus measure right-ascensions or time intervals and also employs the stars of the zenith, which are also separated by given right-ascensional differences.

There are dozens of cuneiform Mesopotamian texts with real observations of eclipses, mainly from Babylonia.

Planetary theory

The Babylonians were the first civilization known to possess a functional theory of the planets. The oldest surviving planetary astronomical text is the Babylonian Venus tablet of Ammisaduqa, a 7th-century BC copy of a list of observations of the motions of the planet Venus that probably dates as early as the second millennium BC.

The Babylonian astrologers also laid the foundations of what would eventually become Western astrology. The Enuma anu enlil, written during the Neo-Assyrian period in the 7th century BC, comprises a list of omens and their relationships with various celestial phenomena including the motions of the planets.


In contrast to the world view presented in Mesopotamian and Assyro-Babylonian literature, particularly in Mesopotamian and Babylonian mythology, very little is known about the cosmology and world view of the ancient Babylonian astrologers and astronomers.

This is largely due to the current fragmentary state of Babylonian planetary theory, and also due to Babylonian astronomy being independent of cosmology at the time. Nevertheless, traces of cosmology can be found in Babylonian literature and mythology.

In Babylonian cosmology, the Earth and the heavens were depicted as a “spatial whole, even one of round shape” with references to “the circumference of heaven and earth” and “the totality of heaven and earth“.

Their worldview was not exactly geocentric either. The idea of geocentrism, where the center of the Earth is the exact center of the universe, did not yet exist in Babylonian cosmology but was established later by the Greek philosopher Aristotle‘s On the Heavens.

In contrast, Babylonian cosmology suggested that the cosmos revolved around circularly with the heavens and the earth being equal and joined as a whole.

The Babylonians and their predecessors, the Sumerians, also believed in a plurality of heaven and earth. This idea dates back to Sumerian incantations of the 2nd millennium BC, which refers to there being seven heavens and seven earths, linked possibly chronologically to the creation by seven generations of gods.


It was a common Mesopotamian belief that gods could and did indicate future events to mankind. This indication of future events was considered to be omens.

The Mesopotamian belief in omens pertains to astronomy and its predecessor astrology because it was a common practice at the time to look to the sky for omens.

The other way to receive omens at the time was to look at animal entrails. This method of recovering omens is classified as a producible omen, meaning it can be produced by humans, but sky omens are produced without human action and therefore seen as much more powerful.

Both producible and unproduceable omens, however, were seen as messages from the gods. Just because gods sent the signs didn’t mean that Mesopotamians believed their fate was sealed either, the belief during this time was that omens were avoidable. In mathematical terms, the Mesopotamians viewed omens as “if x, then y”, where “X” is the protasis and “Y” is the apodosis.

The relationship Mesopotamians had with omens can be seen in the Omen Compendia, a Babylonian text composed starting from the beginning of the second-millennium on-wards.

It is the primary source text that tells us that ancient Mesopotamians saw omens as preventable. The text also contains information on Sumerian rites to avert evil, or “nam-bur-bi”. A term later adopted by the Akkadians as “namburbu”, roughly, “ loosening”.

The god Ea was the one believed to send the omens. Concerning the severity of omens, eclipses were seen as the most dangerous.

The Enuma Anu Enlil is a series of cuneiform tablets that gives insight on different sky omens Babylonian astronomers observed.

Celestial bodies such as the Sun and Moon were given significant power as omens. Reports from Nineveh and Babylon, circa 2500-670 B.C.E., show lunar omens observed by the Mesopotamians.

“When the moon disappears, evil will befall the land. When the moon disappears out of its reckoning, an eclipse will take place”.

The Astrolabes

The astrolabes are one of the earliest documented cuneiform tablets that discuss astronomy and date back to the Old Babylonian Kingdom (not to be mistaken for the later astronomical measurement device of the same name).

They are a list of thirty-six stars connected with the months in a year. Generally considered to be written between 1800-1100 B.C.E.

No complete texts have been found, but there is a modern compilation by Pinches, assembled from texts housed in the British Museum that is considered excellent by other historians who specialize in Babylonian astronomy.

Two other texts concerning the astrolabes that should be mentioned are the Brussels and Berlin compilations. They offer similar information to the Pinches anthology but do contain some differing information from each other.

The thirty-six stars that make up the astrolabes are believed to be derived from the astronomical traditions from three Mesopotamian city-states, Elam, Akkad, and Amurru.

The stars followed and possibly charted by these city-states are identical stars to the ones in the astrolabes. Each region had a set of twelve stars it followed, which combined equals the thirty-six stars in the astrolabes.

The twelve stars of each region also correspond to the months of the year. The two cuneiform texts that provide the information for this claim are the large star listK 250” and “K 8067”.

Both of these tablets were translated and transcribed by Weidner. During the reign of Hammurabi, these three separate traditions were combined. This combining also ushered in a more scientific approach to astronomy as connections to the original three traditions weakened.

The increased use of science in astronomy is evidenced by the traditions from these three regions being arranged in accordance to the paths of the stars of Ea, Anu, and Enlil, an astronomical system contained and discussed in the Mul.apin.


MUL.APIN is a collection of two cuneiform tablets (Tablet 1 and Tablet 2) that document aspects of Babylonian astronomy such as the movement of celestial bodies and records of solstices and eclipses.

Each tablet is also split into smaller sections called Lists. It was comprised in the general time frame of the astrolabes and Enuma Anu Enlil, evidenced by similar themes, mathematical principles, and occurrences.

Tablet 1 houses information that closely parallels information contained in astrolabe B. The similarities between Tablet 1 and astrolabe B show that the authors were inspired by the same source for at least some of the information.

There are six lists of stars on this tablet that relate to sixty constellations in charted paths of the three groups of Babylonian star paths, Ea, Anu, and Enlil. there are also additions to the paths of both Anu and Enlil that are not found in astrolabe B.

The Connection Between a Calendar, Mathematics, and Astronomy

The exploration of the Sun, Moon, and other celestial bodies affected the development of Mesopotamian culture. The study of the sky led to the development of a calendar and advanced mathematics in these societies.

The Babylonians were not the first complex society to develop a calendar globally and in nearby North Africa, The Egyptians developed a calendar of their own.

The Egyptian calendar was solar based, while the Babylonian calendar was lunar based. A potential blend between the two that has been noted by some historians is the adoption of a crude leap year by the Babylonians after the Egyptians developed one.

The Babylonian leap year shares no similarities with the leap year practiced today. it involved the addition of a thirteenth month as a means to re-calibrate the calendar to better match the growing season.

Babylonian priests were the ones responsible for developing new forms of mathematics and did so to better calculate the movements of celestial bodies.

One such priest, Nabu-Rimanni, is the first documented Babylonian astronomer. He was a priest for the moon god and is credited with writing lunar and eclipse computation tables as well as other elaborate mathematical calculations.

The computation tables are organized in seventeen or eighteen tables that document the orbiting speeds of planets and the Moon. His work was later recounted by astronomers during the Seleucid dynasty.

Neo-Babylonian astronomy

Neo-Babylonian astronomy refers to the astronomy developed by Chaldean astronomers during the Neo-Babylonian, Achaemenid, Seleucid, and Parthian periods of Mesopotamian history.

A significant increase in the quality and frequency of Babylonian observations appeared during the reign of Nabonassar (747–734 BC).

The systematic records of ominous phenomena in Babylonian astronomical diaries that began at this time allowed for the discovery of a repeating 18-year Saros cycle of lunar eclipses, for example.

The Greco-Egyptian astronomer Ptolemy later used Nabonassar’s reign to fix the beginning of an era, since he felt that the earliest usable observations began at this time.

The last stages in the development of Babylonian astronomy took place during the time of the Seleucid Empire (323–60 BC). In the 3rd century BC, astronomers began to use “goal-year texts” to predict the motions of the planets.

These texts compiled records of past observations to find repeating occurrences of ominous phenomena for each planet.

About the same time, or shortly afterward, astronomers created mathematical models that allowed them to predict these phenomena directly, without consulting past records.


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