How Did the Maya Track Venus and Its Cycles?

The Maya tracked Venus more carefully than any other planet, and the tables they built for it are the most accurate of all the Maya astronomical tables that survive. The system is recorded on pages 24 and 46 through 50 of the Dresden Codex, one of the four surviving Maya screenfold books, and the practice is well attested in monumental inscriptions at Copan, Tikal, Quirigua, Yaxchilan, and the central lowlands more broadly. This page expands the page on Maya astronomy, stars, planets, and eclipses and links back to the Maya Calendar System and its related page on Maya astronomical cycles and observations.

The synodic period of Venus

Venus is the third-brightest object in the sky, after the Sun and the Moon, and it is the only planet whose naked-eye cycle is straightforward to track. From the perspective of a lowland Maya observer at, say, Tikal or Palenque, Venus traces a regular pattern: it appears as the morning star for 236 days, disappears at superior conjunction for about 8 days (during which time it is too close to the Sun to be seen), reappears as the evening star for 250 days, and disappears at inferior conjunction for about 90 days (during which time it is on the far side of the Sun, then re-emerges as the morning star). The full cycle is 584 days.

The exact synodic period of Venus is 583.92 days, a value that the Maya had effectively captured by the Late Classic period. The Venus tables in the Dresden Codex use a rounded 584-day mean period, with correction rows that account for the difference between 5 × 584 = 2,920 days and the true 5 × 583.92 = 2,919.6 days. The corrections are described in How accurate were Maya astronomical predictions?.

The five-cycle, 2,920-day, and 8-year cycles

The Maya Venus table works in units of 5 synodic periods: 5 × 584 = 2,920 days, an interval that is also exactly 8 haab’ years (8 × 365 = 2,920 days). The 8-year coincidence is the practical reason the cycle was useful. A Maya astronomer who wished to know when Venus would next be the morning star could look up the entry in the table for “first appearance as morning star” in the current 8-year cycle, and the answer would be a specific Long Count date plus a specific tzolk’in and haab’ position.

The same 5-cycle count also yields a near-coincidence with the 13-baktun Calendar Round: 2,920 days × 146 = 426,320 days, while 146 × 8 haab’ = 1,168 haab’ = 426,320 days. The 146 cycles of 5 synodic periods of Venus take up a span of 1,168 haab’ years, which is also exactly 65 Calendar Rounds (65 × 18,980 = 1,233,700 days) minus a small correction. The Venus table and the Calendar Round are therefore deeply integrated, and the Dresden Codex Venus table is laid out in a 65-page ritual-almanac format that ties Venus’s first appearances to specific haab’ and tzolk’in positions.

The Dresden Codex Venus tables

The Venus table proper occupies pages 24 and 46 through 50 of the Dresden Codex. It is organized as a 5-row table that lists, in columns, the 5 synodic periods of Venus, with rows for the 5 phases of the cycle: (1) the morning star (the heliacal rising as the first visible day of the morning star, heliacal rising), (2) the superior conjunction (when Venus is lost in the glare of the Sun, darkness in Maya glosses), (3) the first visible evening star (re-emergence), (4) the inferior conjunction (when Venus is at greatest brilliancy, at greatest brightness or rising again), and (5) the final disappearance as the evening star. The five 584-day periods make up the 2,920-day, 8-year cycle.

The table is followed by a series of correction pages. The most discussed correction is the 4-day adjustment on page 24, in which the running of the 5 × 584 = 2,920-day cycle is reduced by 4 days every 5 cycles, on the principle that the true 5-cycle average is 2,919.6 days, not 2,920. The correction page also notes the relationship between the Venus cycle and the 365-day haab’ year: 5 × 584 = 8 × 365 + 0, so the 8-year cycle integrates the 2,920 days into 8 haab’ without remainder. The 4-day correction over 5 cycles brings the running 2,920-day count down to a 2,919.6-day average that matches the true synodic period.

A second set of correction pages deals with the discrepancy between the 8 haab’ (2,920 days) and the 8 tropical years (2,921.94 days). Over a 40-year span, the haab’ count drifts from the tropical year by about 10 days, and the Venus heliacal rising drifts from its expected position by an equivalent amount. The corrections are usually given as a one-day reduction every 4 haab’ years, applied at the 61st haab’ or so. The same correction appears in the page on Maya astronomy, stars, planets, and eclipses and in the article How accurate were Maya astronomical predictions?.

Venus in the inscriptions

Venus is identified in the inscriptions by a glyph that, in the most common form, combines a star sign with a prefix that reads approximately “star” or “large star,” and the reading Noh Ek — “Great Star” — is widely accepted. Venus’s first appearance as morning star is given a specific glyph, often translated as lhun ch’umil (“the side of the morning star” or “the dawn-side of the star”) or as a prefix to the heliacal-rising table. The identification is supported by iconography: the planet Venus is sometimes shown in the inscriptions with a personified head, often with a prominent nose-ring or a beard of stylized flames.

The best-known Venus inscriptions include the Quirigua Stela E of 756 CE, which records a 9.16.4.0.0 13-baktun period-ending that fell on the day of a Venus heliacal rising; the Copan Stela 11 of 18-Rabbit, which records a Venus event of 763 CE; the Yaxchilan Lintel 25, which shows a war ceremony that was timed to Venus’s first morning-star appearance; and the Tikal Burial 116 of Hasaw Chan K’awil (Ruler A), which records a 9.0.13.0.0 period-ending that coincides with a Venus first-morning-star event of 692 CE.

Venus as war planet and king-patron

The Maya associated Venus with war, kingship, and the Maize God. The heliacal rising of Venus as morning star was, in many inscriptions, the moment a war began, a king was inaugurated, or a captive was sacrificed. The association is preserved in the Popol Vuh, the colonial Yucatec creation myth, in which the Hero Twins of the Popol Vuh become associated with Venus and the Sun respectively. The same association appears in the Dresden Codex, where the heliacal-rising pages of the Venus table are framed as almanacs of war and capture.

The Venus-war-kingship complex is one of the most distinctive features of Maya political religion, and it is integrated into the architecture and iconography of Chichen Itza, Yaxchilan, Tikal, Copan, and Quirigua. The Temple of the Cross at Palenque has been interpreted by David Kelley and Linda Schele as a Venus-observation platform, and the temple’s dedicatory inscriptions record that the building was completed in 692 CE, at the end of a k’atun that coincided with a Venus heliacal rising.

The heliacal rising observation

The heliacal rising of Venus is the moment when the planet first becomes visible above the eastern horizon, just before sunrise, after a period of invisibility. The first morning star rising is the most striking of the Venus events, and it is the one most often recorded in the inscriptions. The Maya tracked it by setting a horizon marker — typically a notched or pointed building, a stairway, or a stela — and watching for the day on which Venus rose over that marker in the hour before sunrise.

The heliacal rising of Venus in the tropics is sensitive to atmospheric conditions, the precise horizon altitude, and the angular separation of the planet from the Sun. The 8-year cycle of the Maya Venus table is, in fact, only approximate: the true heliacal rising of Venus, as observed from a lowland site, can vary by a few days from year to year, and the Maya corrections were calibrated to fit a specific horizon. The system, like the Greek and Babylonian Venus systems, is best understood as a horizon-astronomical instrument rather than as a piece of pure arithmetic.

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