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Mayan Academy of Ancient Astronomy

Xultun Astronomers

Xultun Astronomers

Xultun, Guatemala

Ancient Maya Astronomic Workshop

In the steamy jungles of Guatemala, a team of archeologists led by Boston University’s William Saturno returned in 2011 to a little known site named Xultun. The site has been dated to the 9th century. A member of the team, Max Chamberlain, had been working on a modest building within a residential area that had a large looter’s trench dug through its middle. In March 2010 Max saw the remnants of a wall mural on the west wall of this building, exposed by the looter’s trench. Maya ruins at Xultun were first reported in 1915, and expeditions went in the 1920s and again in the 1970s to map the site’s monuments. These expeditions did not find much except crumbling structures, and over the years looters repeatedly raided the site for artifacts. Saturno’s team in 2010-2011 was not expecting to find much left, especially not wall murals.

Looter's trench into building rubble with exposed mural inside

Looter’s trench into building rubble with exposed mural inside

Max’s building was certainly not one where archeologists anticipated finding wall murals. It was close to the surface rather than deep inside a building complex. Murals are delicate and do not last in the humid lowlands climate. The room was a small structure, six and a half feet wide by six feet long, with a 10 foot tall vaulted roof. The ancient Mayas modified it over several construction phases, the most recent one filled the room with rubble and earth and the final phase was built over it. One remarkable thing was that the Mayas filled in the room through the doorway, rather than collapsing the roof to fill its interior so they could build over the top of it. This method served to preserve the murals inside quite well. The looters carved their trench into the room looking for a tomb, which they did not find. They abandoned their search, leaving a portion of the west wall paintings exposed to weather. It was this faint and barely perceptible mural that Max Chamberlain saw.

William Saturno gets a look at wall mural inside Xultun building

William Saturno gets a look at wall mural inside Xultun building

A surprised William Saturno confirmed that Max was indeed seeing murals. The team continued excavating and during 2011 they cleared out the debris to reveal that three interior walls and the ceiling were covered by murals. The state of preservation varied, depending on how close the murals were to the exterior surface. Looking through the doorway into the room, you see a series of life-size figures seated on the west wall. Their bodies are painted black and they all wear the exact same costume, a white loincloth and a large black “bishop’s miter” hat with a single red feather on the top. These three figures look upward and towards the north wall. On the north wall is another figure painted in orange. He has a more elaborate costume with headdress and jade wristlets. His hand is outstretched holding a stylus, pointing towards another seated figure, the ruler of Xultun.

Xultun mural with one black-colored astronomer and ruler's scribe

Xultun mural with one black-colored astronomer and ruler’s scribe

In the center of the room is a stone bench where the ancient Maya would sit. All the east wall and part of the north wall is covered with numerous small, delicately drawn hieroglyphs of various sizes painted in black and red. These glyphs and bar-and-dot numbers arranged in vertical columns resemble the astronomical charts and ephemeral calendars seen in the Dresden Codex, an ancient Maya screen-fold manuscript originally written in the 11th to 12th century. At the top of these columns are moon glyphs combined with lunar deity heads, followed by columns of three numbers that record elapsed days using periods of the Long Count calendar. Analysis of the numbers showed they calculated lunar semesters, a way the Mayas tracked lunar cycles and predicted eclipses. A set of 27 columns of these lunar tables span across the wall.

Lunar series glyphs with dot-and-bar numbers

Lunar series glyphs with dot-and-bar numbers

To the left of the lunar series, incised thinly over a painted mural figure, is a “ring number.” The only other place ring numbers appear is in the Dresden Codex. This is a count of days with the lowest number circled, making a ring around the number. The lowest number would be the day (kin), indicating how many days to subtract from the current Maya cycle start date of August 11, 3114 BCE. To the Mayas this date is 4 Ahaw 8 Kumk’u. It is not clear how the Xultun astronomers were using ring numbers, but these can be linked to lunar cycles.

On the north wall is a group of four columns painted in red with very large numbers, beginning with a Tzolk’in day followed by a vertical line of five numbers that are some form of Long Count calculation. The time spans express a wide range of accumulated time, some small and others extremely

Long Count style numbers in columns

Long Count style numbers in columns

large. Similar lengthy tallies of days appear as Distance Numbers in the Dresden Codex and on carved monuments. It is possible these tables serve astronomical ends, since they are divisible by 52 (Calendar Round) and 260 (Tzolk’in Calendar). One column contains day numbers that are even multiples of 584, the Maya calculation for the cycle of Venus. Another has numbers evenly divisible by the Maya 819-day cycle related to synodic periods of Jupiter and Saturn. These Long Count style calculations take you back in time as far as 3207 BCE and as far into the future as 3136 CE.

The small building with murals in Xultun appears to be as astronomer’s workshop. The walls were covered with repeated layers of stucco, and the surface upon which the murals are seen is the final layer with many others underneath. This probably served as an astronomer’s blackboard, but instead of erasing their calculations they applied another layer of stucco to make a new surface. The hieroglyphic texts now on the walls at Xultun express dates specifically for 813 or 814 CE. These texts were likely copied and recopied over many generations and

Reconstruction of Xultun astronomer's building

Reconstruction of Xultun astronomer’s building

updated periodically from observational data of eclipses, lunar and planetary cycles. The Xultun murals are the earliest example yet found of such Maya astronomical calculations.

Did Saturno and Chamberlain discover a Classic Period ancient Mayan astronomical academy? Because of the small building’s characteristics, it might have been part of a residence for astronomers. You can imagine them gathered in the room, perched on the stone bench and painting their intricate glyphs and numeric calculations with black and red plant dyes on the fresh stucco wall. One man dressed more elaborately, perhaps the ruler’s scribe, poises his stylus waiting the ruler’s words. The ruler in trance, channeling a Maya deity, reveals mystical understandings of sacred calendric cycles that the astronomers will use in making their calculations.

Xultun mural reconstruction seated ruler

Xultun mural reconstruction seated ruler

Xultun mural reconstruction of kneeling scribe

Xultun mural reconstruction of kneeling scribe



  1. I’ve read several accounts of the Xultun murals and this is the clearest, most thorough, and pleasure to read. Many thanks for the article.

  2. Great article and an enjoyable read. I love the topic.

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