Maya Astronomy, Stars, Planets, and Eclipses

Maya astronomy was a practical, quantitative science that combined naked-eye observation with the mathematical systems described on the Maya number system and the concept of zero page, the calendrical structures that the Maya calendar system overview introduces, and the writing system surveyed in Maya writing, language, and books. The Maya tracked the motions of the Sun, Moon, Venus, Mars, Jupiter, and Saturn; built a warning system for solar and lunar eclipses; identified zenith-passage days for each major site; oriented temples and pyramids to sunrise and sunset on the solstices and equinoxes; and used almanacs to time rituals of war, bloodletting, and political ceremony. The page on astronomical cycles and observations is the natural companion to this page from the calendar overview.

The instruments: no telescopes, only the horizon and the codex

The Maya observed the sky entirely with the naked eye, but they had access to a wide range of horizontal and vertical reference markers. A horizon calibrated over many years, with stone alignments set into temple doorways and across plazas, was a sufficiently precise instrument. The horizon mountains of the Peten lowlands, the limestone ridges of the Puuc hills, and the volcanic cones of the highlands all gave natural points against which to sight. The horizontal gnomon of a stela pair — a standing stone and a circular altar that, viewed together, marked the rising or setting of a star on a given date — served the same function. Vertical gnomon use is also attested: a vertical stick set on a flat horizontal surface could be used to find the day of zenith passage by the disappearance of its noon shadow.

Within the codices, the instruments became the tables. The Dresden Codex, the most important of the four surviving Maya books, contains the Venus tables (pp. 24, 46–50), the Mars tables (pp. 43–45), the lunar tables (pp. 51–58), the eclipse tables (pp. 51–58), and the multiplication and correction tables (pp. 49–56) on which Maya astronomical arithmetic was based. The Madrid Codex contains the almanacs of the agricultural year and a Venus table. The Paris and Grolier codices contain almanacs of mixed ritual and astronomical content. The almanacs of these four books are the most complete surviving record of a pre-telescopic naked-eye astronomy anywhere in the world.

The Sun and the haab’ year

The 365-day haab’ is a “vague” solar year — it has no leap correction — and it drifts against the tropical year by about 0.2422 days per annum, or one day every four years. The haab’ was therefore unsuitable for the prediction of solstices, equinoxes, and the heliacal rising of bright stars without correction. The Maya used several strategies to handle this drift.

The first was practical: for agricultural purposes, a vague year that was off by a few days was not a serious problem. The first rains in the lowlands came over a window of weeks, not days, and an off-by-a-week planting date was adequate. The second was calendrical: by combining the haab’ with the 260-day tzolk’in to form the 18,980-day Calendar Round, the Maya could refer to a specific day of the year unambiguously within a 52-year cycle. The third was corrective: the Dresden Codex includes correction cycles of 4 × 365 = 1,460 days, of 365 + 1,040 haab’ = 379,965 days, and of 1,296 haab’ = 473,140 days that resynchronized the haab’ to the tropical year. The accuracy of these corrections is detailed in How accurate were Maya astronomical predictions?.

The solar year was also studied through the zenith-passage days. At any site in the tropics, the Sun passes directly overhead twice a year, on dates that depend on the latitude. The shadow of a vertical stick at true local noon disappears on those two days. At Copan, for example, the zenith passage occurs on approximately April 30 and August 13. Many Maya sites had carved, painted, or built-in markers that designated those days, and ceremonies of the New Year were scheduled around them. The Caracol tower at Chichen Itza, the Temple of the Cross at Palenque, the E-Group at Uaxactun, and the Cenote of Sacrifice at Chichen all have alignments to zenith passage.

The Moon: the 405-lunation cycle

Lunar tables in the Dresden Codex record the half-month of 11960 days and the 46-month, 11,960-day eclipse cycle — an interval exactly six synodic months of 29.53 days long, which is the minimum separation between two possible eclipses of the same type. Six synodic months is, to within an hour, 177.18 days, but the Maya used 178 days (the half of 11,960) as a convenient round number. The full cycle of 405 lunations (11,960 days, or about 32.75 tropical years) was the working period of the eclipse warning system: any eclipse possible at the start of the cycle is possible, six months later, at the midpoint.

The Maya were also aware of the 46-month variation in the length of the eclipse year and the half-month. The lunar tables include correction pages that adjust the eclipse warning for the 6-month or 12-month half-period of the cycle. The system allowed a Maya astronomer to look up a future date, see whether a possible eclipse was in play, and confirm the warning with a sighting observation. The accuracy of the lunar tables is treated in How accurate were Maya astronomical predictions?.

The Maya also kept track of the Moon’s phase and age, recording the 29- or 30-day lunation, the moon number within a half-cycle, and a coefficient for the lunation’s position in the 9-CR / 8-CR 46-month cycle. The Classic period inscriptions include a Lunar Series — a standard block of glyphs added to Initial Series dates that records these parameters. Famous examples include the Lunar Series on Yaxchilan Lintel 25 and the elaborate 8-CR records of Palenque, both of which are illustrated in Maya stelae, altars, and stone monuments.

Venus: morning star, evening star, and war star

Venus was the most carefully tracked of the planets, and the one with the deepest ritual significance. The planet appears as a morning star for 236 days, disappears for about 8 days in superior conjunction, reappears as an evening star for 250 days, disappears again for about 90 days in inferior conjunction, and reappears as a morning star — completing a 584-day synodic cycle. The cycle has a mean error of 0.08 days per revolution, accumulated to about 0.4 days per 5 cycles, and was tracked to within hours over decades.

The Dresden Codex contains the most complete Maya Venus table. It records 5 synodic periods of 584 days = 2,920 days = 8 years (almost — 8 haab’ are 2,920 days, and 8 × 365.2422 tropical years are 2,921.94 days, so the 2,920-day count is off by about 1.94 days per 8 years, or one day in 4 years). The Venus table includes correction pages that adjust the running of the 5-cycle count for this drift. The detailed ritual and political use of the Venus table is described in How did the Maya track Venus and its cycles?.

Venus’s name in Maya inscriptions is usually read as Noh Ek, the “Great Star.” Its identification as both the morning and evening star is preserved in glyphic texts. It was associated with warfare, kingship, and the Maize God. The heliacal rising of Venus in particular was a powerful omen, and many inscriptions record that a war was begun or a king was inaugurated on the morning star’s first appearance after inferior conjunction. The visual record of Venus is integrated into the Maya murals of Bonampak, San Bartolo, and Calakmul.

Mars, Jupiter, and Saturn

The Dresden Codex Mars tables (pp. 43–45) record a 780-day cycle that is, to within hours, the synodic period of Mars (779.94 days). The cycle was used to time wars, presumably because Mars was a war planet in the same way that Venus was a war-morning star. Jupiter was tracked with a 399-day cycle in some inscriptions and a 442-day cycle in others; the synodic period of Jupiter is 398.88 days. Saturn was tracked with a 378-day cycle, very close to the synodic period of 378.09 days. The four-planet calendar at Palenque, the famous 819-day cycle, brings these planets back into conjunction with the 260-day tzolk’in at intervals of 819, 1,638, 2,457 days and so on. The arithmetic is treated in Maya number system and the concept of zero.

Stars: the Pleiades, Orion, and the Milky Way

The Pleiades, called Motz in some colonial dictionaries and recorded in inscriptions as a cluster of stars visible in the east before dawn in late April, were important for the beginning of the rainy season and the start of the agricultural year. Orion’s belt, identified with the hearth-stones of creation, appears in the Popol Vuh, the Maya creation myth. The Milky Way, sometimes read as a celestial river or as a path along which the sun and the dead travelled at night, appears in the inscriptions as the Wakah-Chan, the “raised-up sky” or the “upended tree of the world.” Several inscriptions at Yaxchilan and Palenque refer to the entry of a god or king into the Milky Way at the time of death.

Eclipses: the 11,960-day cycle

Solar and lunar eclipses were both tracked. The basic eclipse-warning cycle was the 11,960-day (405-lunation, 46-month) count, a 32.75-year interval after which the same eclipse-possible dates recur in the same order. The Dresden Codex uses this cycle, with correction rows, to issue warnings up to about 78 years in advance. The warnings identify dates on which a solar or lunar eclipse was possible — that is, dates when the Sun and Moon were within about 18 degrees of the lunar node. The actual occurrence of an eclipse still required a visual confirmation, but the warning narrowed the search to a specific 18-day window. The system is comparable in accuracy to the Greek Saros cycle (about 18 years, 11 days, 8 hours) and to the Chinese prediction system of the same period. The detail of Maya eclipse prediction is treated in the calendar article on Maya solar eclipse prediction.

Archaeoastronomy: buildings as instruments

The orientation of major Maya buildings is a rich record of which astronomical events mattered to which community. At Chichen Itza, the Caracol tower — a circular structure on two raised platforms with windows aligned to sunset and to Venus — is one of the best-studied Maya observatories. The Temple of Kukulcan there, a pyramid with four faces and nine terraces, casts a serpent-shaped shadow at the equinox sunset, with the shadow of the balustrade forming the undulating body of a snake that connects to a stone serpent head at the base of the staircase. The effect was not accidental; the building is dated to the tenth or eleventh century, after the Classic period, and reflects a deliberate architectural-astronomical program.

The Temple of the Cross, the Temple of the Sun, and the Temple of the Foliated Cross at Palenque are oriented to the rising of the Sun on the solstices and equinoxes and to specific stars. The Cross Group of temples at Palenque is also keyed to the 819-day cycle, with the three temples representing the three hearth-stones of the Maya creation. The E-Group complexes of the central lowlands — named for the type site of Uaxactun — consist of a pyramid to the west of a long plaza, with three small temples on the pyramid’s southern face, and a fourth, long structure on the eastern side of the plaza. From the western pyramid, the Sun rises over the three small temples on the equinoxes and over the two outer temples on the solstices. Dozens of similar E-Groups are known across the lowlands, dating to the Middle and Late Preclassic. The classic survey is that of Anthony Aveni, who developed the field of Mesoamerican archaeoastronomy in the 1970s and 1980s.

Sources

Aveni, A. F. (2001). Skywatchers of Ancient Mexico. University of Texas Press. — link
Saturno, W. A. et al. (2012). Ancient Maya astronomical tables from Xultun, Guatemala. Science 336 (6082), 714–717. — link
Berlin, E. A. & Berlin, B. (1996). Medical Ethnobiology of the Highland Maya of Chiapas, Mexico. Princeton University Press. — link
Sharer, R. J. & Traxler, L. P. (2006). The Ancient Maya (6th ed.). Stanford University Press. — link
Coe, M. D. (1993). The Maya (5th ed.). Thames & Hudson. — link