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date: 29 November 2020

The Planets in Aztec Culturefree

  • Susan MilbrathSusan MilbrathFlorida Museum of Natural History


The Spanish chronicles do not mention planets other than Venus, although they compare certain Aztec gods with classical gods such as Jupiter and Mars. Creation myths recorded by the Spanish chroniclers frequently name Venus gods, most notably Ehecatl-Quetzalcoatl and Tlahuizcalpantecuhtli. The focus on Venus seen in these texts is also mirrored in colonial period Aztec codices, which feature several Venus gods as rulers of calendar periods associated with the 260-day calendar. The famous Aztec Calendar Stone represents Venus symbols prominently in an image showing the predicted demise of the Sun in an eternal solar eclipse, to be accompanied by earthquakes. Venus is apparently seen as the cause of a total solar eclipse in the Codex Borgia, a pre-conquest codex from Tlaxcala, a community neighboring the Aztecs in central Mexico. Although no pre-conquest Aztec codices survive, the painted screenfold books attributed to neighboring communities in central Mexico provide evidence of the kinds of almanacs that were probably also found in Preconquest Aztec screenfold books. The Codex Borgia has two Venus almanacs associated with heliacal rise events and another focusing on dates that coordinate with events involving Venus and possibly other planets. A unique narrative in the Codex Borgia traces Venus over the course of a year, representing different aspects of the synodical cycle. The transformation of Venus in the narrative is evidenced by subtle changes in the Venus god, Quetzalcoatl, who represents the planet Venus throughout the synodical cycle. Another god, Tlahuizcalpantecuhtli (“lord of dawn”), appears in the narrative associated with Venus as the morning star and also is represented in a death aspect during superior conjunction. This is in keeping with Aztec legends that tell how the Sun killed Tlahuizcalpantecuhtli with his solar rays. The Borgia narrative also helps identify Xolotl as the planet Mercury and provides hints about other planets that may be linked with different aspects of Tezcatlipoca, an Aztec god who ruled the night sky.

Spanish chroniclers documented Aztec cosmology and religion shortly after the conquest of central Mexico in 1521. The most important accounts were written by Aztec scribes, who were trained by Spanish clerics to transcribe texts in their language (Nahuatl). Friar Bernardino de Sahagún, a mid-16th-century chronicler, recorded the most detailed information available on Aztec beliefs about the Sun, Moon, and Venus, but provided no information on other planets. Aztec religion emphasized worship of celestial deities representing the Sun, Moon, and Venus in the guise of Quetzalcoatl (“quetzal-feathered serpent”). There are a number of deities associated with the Moon, but the most prominent is Coyolxauhqui, a goddess conquered by Huitzilopochtli (“hummingbird of the south”), the solar god who led the Aztecs on the migration from their homeland Aztlan to the Valley of Mexico, where they founded their capital, Tenochtitlan (Milbrath, 1997; Nicholson, 1971).

Venus in Aztec Myths and Rituals

Aztec priests knew when Venus would first appear as the morning star, and they predicted ominous auguries based on the heliacal rise date in their 260-day divination calendar (tonalpohualli), as seen in the Codex Chimalpopoca. For example, old people would be afflicted when Venus first appeared on the day 1 Crocodile (Cipactli), but there would be drought when the heliacal rise fell on the day 1 Water (Atl; Aveni, 1992, p. 70). To avert such calamities, captive warriors were killed and their blood was offered to Venus when it first emerged as the morning star (Sahagún, 1950–1982, vol. VII, p. 12).

In Aztec cosmology, Venus as Quetzalcoatl plays a key role in the guise of Ehecatl (“wind”), representing winds originating from all four directions (Sahagún, 1950–1982, vol. VII, p. 68). He plays a role in the birth of the Aztec Sun god created in a cosmic fire at Teotihuacan, for when Tonatiuh (“Sun”) was unable to move across the sky, Ehecatl’s wind power carried the Sun up in the sky (Sahagún, 1950–1982, vol. VII, p. 8). Another Venus god appears in the Anales de Cuauhtitlán version of the creation of the fifth Sun. Tlahuizcalpantecuhtli (“lord of dawn”) threatened the Sun to make him move across the sky and the Sun retaliated, shooting flaming arrows and obliterating the lord of dawn, blotting out the light of the morning star (Bierhorst, 1992, p. 149).

Venus gods are prominent as rulers of calendar periods in Aztec codices such as the Codex Borbonicus and Codex Telleriano-Remensis. Quetzalcoatl was honored in two of the 18 festivals that divided the year into 20-day veintenas periods, but other Venus gods are not represented in these festivals (Nicholson, 1971, Table 4). Venus gods seem to play a more important role as patrons of three of the 13-day trecenas in the 260-day tonalpohualli (Caso, 1971, p. 338). Tlahuizcalpantecuhtli ruled the trecena beginning with the day 1 Serpent (Quiñones Keber, 1995, p. 262). Itztlacolhuiqui (“curved obsidian blade”), ruler of the trecena beginning 1 Lizard, seems to be another transformation of the morning star (Quiñones Keber, 1995, pp. 178, 264). Yet another Venus god, Ehecatl-Quetzalcoatl, is the lord of the trecena beginning 1 Jaguar (Quiñones Keber, 1995, p. 258). Ehecatl is sometimes specifically identified with the evening star (Šprajc, 1993a, p. 35, 1993b, pp. S35–S36, 2008, p. 9), but he also appears in imagery of the morning star in the Codex Borgia (Milbrath, 2013). Among the many Venus gods who are trecena patrons, only the trecena of Ehecatl-Quetzalcoatl (1 Jaguar) appears among the ominous heliacal rise dates recorded in the Codex Chimalpopoca (Aveni, 1992, p. 70).

Quetzalcoatl’s transformation into Venus seems to be a core element in different accounts linking him with the legendary ruler of Tula (Nicholson, 2001, pp. 251–251). Topiltzin-Quetzalcoatl was driven out of the city by his archrival, Tezcatlipoca (“smoking mirror”), and was forced to travel east to the sea, where he was transformed into the morning star (Durán, 1964, p. 329). In some accounts, his heart was carried up to heaven to become both the morning and evening stars, but most often he is transformed into the morning star. In the Anales de Cuauhtitlán, Quetzalcoatl set himself afire when he reached the ocean and his heart rose up into heaven as the morning star (Bierhorst, 1992, p. 36; Seler, 1904, pp. 364–365). Before emerging as the morning star, Quetzalcoatl descended into the underworld for 8 days, evoking a link with the mean number of days Venus is invisible in inferior conjunction (Aveni, 1992, pp. 68–70; Aveni, 2001, p. 186). Ivan Šprajc (1993a, p. 29) points out that this myth shows that Quetzalcoatl played the role of the evening star, but he also finds evidence of an association with the morning star, as in the Codex-Telleriano Remensis. The Venus narrative in the Codex Borgia (pp. 29–46) suggests that Quetzalcoatl represents Venus throughout the synodical cycle (Milbrath, 2013).

Certain Aztec rituals were timed by Venus events. In addition to the previously mentioned sacrifice of victims at the first appearance of the morning star, the Atamalcualiztli ceremony was performed every 8 years to synchronize the Venus cycle with the solar year (Seler, 1990–2000, vol. III, pp. 278–280; Galindo Trejo, 1994, p. 84). The lunar aspect of the ceremony is also noteworthy. Five Venus cycles are 2 days short of 8 solar years and 4 days short of 99 synodical lunar months, a cycle called the Octaeteris in ancient Greece (Aveni, 1992, p. 95). In Mesoamerica, this cycle of 2,920 days was reckoned as five Venus cycles of 584 days equated with 8 vague years (365-day years), and approximately 99 lunar months (5 × 584 = 8 × 365 = 99 × 29.49). Sahagún’s (1950–1982, vol. II, pp. 238–239) song of Atamalcualiztli features Piltzintecuhtli, Xochiquetzal, and Quetzalcoatl, deities related to the Sun, Moon, and Venus, the three astronomical bodies observed in timing the festival every 8 years (Milbrath, 2013, pp. 94–95, 143, note 91).

The Atamalcualiztli ceremony took place as the rainy season came to a close, and most likely it was timed by a specific seasonal position of Venus. According to Sahagún (1950–1982, vol. II, pp. 177–178), Atamalcualiztli was performed in Hueypachtli or Quecholli, two sequential veintena festivals (20-day “months”) that represented a 40-day period spanning from October 12 to November 20 (1519) in the Julian calendar or 10 days later in the Gregorian calendar (Milbrath, 2013, p. 119, note 50, Table 2.3). Descriptions of the ceremony recorded by Sahagún note that there was a pool of water filled with serpents and frogs, and people dressed up as birds, hummingbirds, butterflies, and flies, costumes featuring creatures seen during the rainy season. These are all animals that would disappear from the landscape when the dry season commenced in Quecholli.

In addition to this seasonal imagery, it seems likely that the position of Venus along the ecliptic may also have been significant because sidereal intervals related to specific planets are known to be important in Maya calendrics (Aveni, Bricker, & Bricker, 2003). Sidereal positioning may be implied in an Aztec song that Sahagún (1950–1982, vol. II, p. 238) recorded for the Atamacualiztli ceremony, which includes this passage: “You stand yourself up, Near the market place stars, [You] are the lord, [You] Quetzalcoatl.” This suggests that Venus-Quetzalcoatl was positioned near the marketplace stars, the constellation (tianquiztli) illustrated in Sahagún’s (1997, p. 154, note 9) Primeros Memoriales by a cluster of stars that seems to represent the Pleiades (Aveni, 2001, p. 33, Figure 10a; Sahagún, 1993, folio 282r). The Codex Telleriano-Remensis notes that the marketplace stars ruled the year except during the festival of Tecuilhuitontli, a festival that began on June 24 in the Julian calendar (July 14 Gregorian) when the Pleiades would have shifted to the morning sky (Aveni, 2001, Table 10; Quiñones Keber, 1995, p. 175). The song recorded by Sahagún relates to a ceremony that took place in October or November, which means it cannot refer to a conjunction event because Venus passes by the Pleiades only between the March equinox and June solstice, regardless of the phase in its synodical cycle (Milbrath, 1999, p. 210). Šprajc (1993a, p. 25) points out that the planet Venus would be seen near the Pleiades in June only as the morning star, whereas in March through April, if the planet was seen near the Pleiades, it would be the evening star. Because the cycle of the Octaeteris coincides with Atamalcualiztli, performed every 8 years, Venus would be seen in the same phase in a similar sidereal position around the same time of year. The ceremony in mid- October or early November may have focused on the position of Venus at a time when the Pleiades was visible for the longest period during the night (dusk rise in the east on November 1, dawn set in west on November 18 around 1500 ad; Aveni, 2001, Table 10).

Colonial sources provide many insights about the role of the planet Venus in Aztec ceremonies and religion, but understanding subtle Venus transformations has been challenging because Spanish chroniclers record only the most basic information, and all the surviving Aztec painted books are from the colonial period. Although the majority of accounts focus on Quetzalcoatl’s transformation into the morning star, Quetzalcoatl as the evening star plays an important role in agricultural fertility and maize agriculture. Ivan Šprajc (1993a, pp. 26–27) notes that the evening star has a natural association with the north and rainfall because only as the evening star does Venus achieve a maximum northern declination that exceeds that of the summer solstice Sun. He also argues that Quetzalcoatl is more closely linked with the evening star, while Tlahuizcalpantecuhtli is related to both the morning and evening stars (Šprajc, 1993a, pp. 29, 35, 1993b, 1996). Nonetheless, Tlahuizcalpantecuhtli’s main role is as the morning star, providing the “first light” before sunrise (Quiñones Keber, 1995, p. 75), a role played on Borgia 33 and 53–54, but he also can represent the dead morning star when Venus was in superior conjunction, as on Borgia 45 when the transformation of the morning star to the evening star is seen to take place (Milbrath, 2013, pp. 96–98, plate 17).

The transformation of one Venus god into another is also seen in the Historia de Culhuacán, where Tlahuizcalpantecuhtli is transformed into Itztlacolhuiqui, the god of frost (Quiñones Keber, 1995, p. 178; Seler, 1963, vol. II, p. 205). Šprajc (1993a, pp. 31–34) argues that this god of frost represents the evening star and is also a seasonal aspect of Venus associated with the fall when frost first appears during the festival of Ochpaniztli. However, Itztlacolhuiqui has also been identified as the morning star aspect of a multifaceted deity known as Tezcatlipoca (Milbrath, 2013, pp. 65, 133, note 103; Olivier, 2003, p. 123).

Other Planets in Aztec Art

Aztec sculpture dating to pre-Columbian times and painted books and chronicles of the early colonial period do not clearly identify planets other than Venus. Friar Toribio de Motolinía (1903, p. 55) said their divination calendar was ruled by 13 planets, but he makes no specific identifications, and the reference seems to be to the 13-day periods (trecenas) subdividing the 260-day divination calendar. Writing in 1556, Francisco Cervantes de Salazar (1971, pp. 143–144) mentions three planets associated with Aztec deities, noting that the Sun was the most highly esteemed “planet,” and the gods Tezcatlipoca (“smoking mirror”) and the rain god (Tlaloc) were also planets, but does not attempt to identify these planets. Writing between 1580 and 1581, Friar Diego Durán (1971, p. 266) compares Tlaloc, the god of thunder and lightning, to the Roman god Jupiter, apparently because they controlled similar realms. Sahagún (1985, pp. 31, 36) identifies Tezcatlipoca as “another Jupiter,” and the goddess Tlazolteotl as “another Venus,” an apparent attempt to correlate the Roman deities of antiquity with Mesoamerican counterparts. And Friar Juan de Torquemada’s (1986, vol. I, p. 78, vol. II, p. 40) Monarquía Indiana, completed around 1611, links Tezcatlipoca to Jupiter, again referencing the classical ruler of the heavens rather than the actual planet Jupiter. In a similar vein, Torquemada compares Huitzilopochtli to the Roman god of war, Mars. Despite the tenuous nature of these links with the deified planets of classical antiquity, there may actually be some connection between Tezcatlipoca and the planet Jupiter, based on Maya sources and astronomical events that suggest a link between Jupiter and the god Kawil, the Maya counterpart for Tezcatlipoca (Milbrath, 1999, pp. 227–240, 2005, 2014b).

Inspired by chronicles mentioning the Roman god, Jupiter, Alberto Escalona Ramos (1940, pp. 295, 329, 336), a civil engineer with an interest in astronomy, also proposed that Jupiter could be linked with Tezcatlipoca. Although his methodology is questionable, his monograph represents one of the first attempts to systematically identify the planets in Aztec cosmology, and his identification of the planet Jupiter may be correct, although Tezcatlipoca has multiple avatars, at least one of which may be a lunar god (Milbrath, 2013, pp. 61–65). Escalona Ramos (1940, p. 341) may also have correctly linked Xolotl with the planet Mercury. Xolotl (“monster”), a calendar deity who also appears in Sahagún’s account of the Sun’s creation, has been interpreted as the evening star (Nicholson, 2001, p. 284; Quiñones Keber, 1995, p. 184; Šprajc, 1993a, p. 30, 1996, p. 89), but more likely represents the planet Mercury, as has been proposed using other lines of evidence (González Torres, 1975, pp. 117, 2002; Milbrath, 2013, pp. 108–109).

Escalona Ramos attempted to identify other planets but here his ideas have not been confirmed in independent studies by other scholars. For example, he suggested that the red planet Mars was linked with both Tlaloc and Xipe Totec, based on the red color he attributes to these gods, even though Tlaloc is rarely represented with a red body, and he equated Chalchuitlicue with Mars, seeming to offer contradictory identifications (Escalona Ramos, 1940, p. 359). On similarly shaky ground, he linked the fire god Xiuhtecuhtli with Saturn (Escalona Ramos, 1940, pp. 315–317). His study never gained traction with the academic community, and most scholars have avoided linking Aztec gods with planets other than Venus (but see González Torres, 1975, pp. 117–118; Kelley, 1980; Milbrath, 2013).

David Kelley (1980) attempted to identify the planets in Mesoamerican cosmology by using deity calendar names in the 260-day calendar as indications of specific intervals counting from a base date of 12 Lamat 1 Pop, a reconstructed Calendar Round date embedded in a table in a Maya painted book known as the Madrid Codex (Kelley, 1980, p. S16, Tables IV, V). Not only is a Maya date used to argue for a relationship with Aztec deities, a questionable premise, another weakness is that the 12 Lamat date has no special prominence in the table. In fact, the 13 Ahau 13 Cumku would more likely be the base, not only because it is the last date in the table but also because it is one of the few complete Calendar Round inscriptions in the codex (others are identified in Vail & Bricker, 2004, figure 7.2, Table 7.2).

Kelley (1980, Table V) linked Xolotl with Venus, an accepted identification at the time he was writing, but other identifications depart from widely accepted evidence. He identified Quetzalcoatl-Kukulcan as Mercury, based on calculations using the dubious 12 Lamat 1 Pop date and the calendar name 9 Wind to establish the 115.8774 mean synodical period of Mercury. He argued that this name refers to the period of inferior conjunction, based on one version of Quetzalcoatl’s descent in the underworld to recover the bones of his father that the Spanish chronicler Mendieta linked to Mercury. He links Quetzalcoatl’s other calendar name, 1 Reed, with Mercury’s period of superior conjunction, reckoned as a multiple reflecting a 405.5709-day interval counted from 12 Lamat 1 Pop (Kelley, 1980, Table V). Kelley related the Aztec rain god Tlaloc and his Mixtec counterpart (1 Rain) to the planet Mercury in inferior conjunction, and the Corn God, Centeotl, to Venus in inferior conjunction at the autumn equinox. Although his hypothesis regarding calendar names as markers for calendric intervals is intriguing, there is no evidence of a base date in Aztec sources, the Maya did not use calendar names for individual deities, and the Maya base date itself is questionable as it is not a Calendar Round date and it is not in a significant position in the table. Furthermore, number counts are easily manipulated to evoke a link with the synodical periods of specific planets, as can be seen in numerical correlations with planetary cycles that Escalona Ramos (1940, pp. 358–371) derived by counting design elements such as feathers on the Aztec Calendar Stone.

The Aztec Calendar Stone

The Aztec Calendar Stone (Sun Stone), one of the largest and certainly the most complex Aztec sculptures known to date (2019), clearly emphasizes astronomical imagery (Figure 1). The stone depicts solar rays framing the Sun god, Tonatiuh, the fifth Sun symbolizing the Aztec epoch, here seen in a death aspect with a knife tongue (Milbrath, 2017). The author’s research links this imagery with the predicted death of the Sun in an apocalypse to be accompanied by earthquakes and a total solar eclipse. Tonatiuh appears in the center of the stone surrounded by faces that represent the “Suns” of four previous world ages, namely Ehecatl-Quetzalcoatl, Tlaloc, Chalchuitlicue, and Tezcatlipoca. In the legend of the five Suns, the four previous Suns had been destroyed in cataclysmic events, such as hurricanes, a flood, and a rain of volcanic fire. In the Historia de los Mexicanos por sus pinturas, possibly written by Motolinía, Tezcatlipoca is the first Sun, Quetzalcoatl is the second, Tlaloc is the third, the fourth is Chalchiutlicue, identified by the chronicler as the Moon goddess, and the fifth and final Sun is the Aztec Sun god, Tonatiuh (Garibay, 1973, pp. 30–35). Although the Sun and Moon are not planets in the proper sense of the word, it seems that they were included among the planetary deities in the Earth-centered universe of the Aztecs. Similar beliefs, of course, can be found in classical antiquity, and it seems that the Maya also included the Sun and Moon in a group of planetary deities numbering seven (Milbrath, 1999, pp. 244–247).

Possibly bright “planets” (including the Moon) were visualized as the four Suns destroyed in earlier epochs, each destruction event associated with a different calendar date. If Chalchuitlicue represents the Moon and Ehecatl-Quetzalcoatl is Venus, then at least two of the four deities associated with previous world ages were visualized as bright planets. Since Tezcatlipoca has multiple identities in the myth of the four Tezcatlipocas, he may be identified with another planet or the Moon in a masculine aspect. Furthermore, an astronomical context for the representation of the legend of the five Suns on the Calendar Stone seems likely because constellations are pecked into the left side of the stone and the rays of the Sun disk are framed by two star-snouted fire serpents (Xiuhcoatl), which seem to represent a specific constellation, most likely Scorpius (Milbrath, 2013, p. 144, note 100; Milbrath, 2017, pp. 21–22). The serpent jaws carry the Sun god on the lower right and the Fire God (Xiuhtecuhtli) on the lower left.

Figure 1. Aztec Calendar Stone, with the Sun god framed by 4 Earthquake symbol, enclosing the gods representing the four previous world ages. Drawing originally published in Nuttall (1901).

Although not illustrated here, the sides of the stone clearly show a band of Venus symbols (Beyer, 1921/2010, Figure 48; Milbrath, 2017, Figure 4). Long ago, Hernan Beyer (1921/2010, p. 144, Figures 48–50) compared these symbols to representations on other monuments that show Venus as a central star framed by knives and rays with pendant stars. Quincunx symbols depicted by radial groups of five dots could be symbols for the number five and are clearly linked with Venus because the lord of dawn, Tlahuizcalpantecuhtli, wears this design as face paint. Eight quincunx symbols in cartouches are positioned in between eight solar rays on the Calendar Stone, perhaps evoking a numerical equation between 8 solar years and five Venus cycles (Milbrath, 2017, pp. 20–21). In an inner circle, framing a ring with the 20-day signs used in the Aztec calendar, 52 quincunx symbols (40 with 12 hidden behind the four largest solar rays) suggest a possible link with the Calendar Round of 52 solar years, for the quincunx is also a symbol for both “turquoise” and “year” (Milbrath, 2017, p. 20). Enrique Juan Palacios (1921/2010, pp. 171–174) argued that these quincunx symbols refer to a double Calendar Round (2 × 52 years = 104 years = 65 Venus cycles), but the way he arrives at this total seems contrived. Such numerical equations must remain speculative, but Venus clearly plays an important role in the symbolism of the Aztec Calendar Stone.

Cecelia Klein (1976, p. 12; Klein, 2010, p. 214) concluded that the Calendar Stone refers to “the darkened sun and the planet Venus at the moment of cyclic destruction and completion.” She links the central imagery to the death of the fifth Sun at the completion of a Venus cycle at the end of the 52-year Calendar Round. Aztec legends speak not only of the birth of the fifth Sun at Teotihuacan, but also describe its future demise, an ominous event that would end the Aztec world with earthquakes and a solar eclipse on the date 4 Olin (4 Earthquake). Although Klein did not specify any link with eclipse iconography, the date 4 Earthquake featured at the center of the stone (surrounding the Sun god’s face) is itself a reference to the date of the demise of the fifth Sun during a total solar eclipse. The Codex Telleriano-Remensis notes that if the Earth trembled and the Sun was eclipsed on this date, the world would come to an end, bringing to a close the reign of the fifth Sun with the descent of the Tzitzimime (Milbrath, 2017, p. 17; Quiñones Keber, 1995, p. 261). The descent of these demons of darkness is directly associated with accounts of solar eclipses (Sahagún, 1950–1982, vol. VII, p. 2). An apocalyptic eclipse event seems to be represented on the Calendar Stone for the Sun god shown in a death aspect with a protruding tongue. He is framed by the claws of the Tzitzimime and the date 4 Earthquake, the ominous date when the Sun would be permanently eclipsed (Milbrath, 2017). Venus imagery on the rim of the stone is also in keeping with a reference to a solar eclipse because Venus was believed to be the cause of solar eclipses in Mesoamerica, no doubt because Venus is usually seen near the Sun during a total solar eclipse (Milbrath, 2007, 2013, pp. 44, 107–108).

Venus in the Codex Borgia

The Codex Borgia, a rare pre-Columbian screenfold book from Tlaxcala, an independent Nahuatl-speaking state in the heart of central Mexico, provides evidence for identifying a number of different Venus gods (Milbrath, 2013). The codex has several Venus almanacs and many images related to the astronomical cycles of Venus. The renowned German scholar Eduard Seler (1904, 1963) first recognized the Venus almanac on Borgia pages 53–54, and he identified other Venus deities in a unique narrative on Borgia pages 29–46. Seler (1904–1909, 1963) studied the Codex Borgia using Aztec sources to identify deities related to astronomical events in the codex, and he recognized a number of different manifestations of Venus-Quetzalcoatl and the god of the morning star, Tlahuizcalpantecuhtli, wearing his distinctive quincunx face paint (Seler, 1963, vol. I, pp. 190, 212, Figures 436, 440).

Venus is a focal point for a number of Borgia almanacs, and early work by Seler (1904) demonstrated that an almanac on pages 53–54 is a record of five Venus cycles (5 x 584 days), and closely related almanacs have also been recognized in the Codex Cospi and Vaticanus B (Aguilera, 1988; Aveni, 1999; Boone, 2007, pp. 151–155). Each of the five Borgia deities representing the newly risen morning star are aspects of Tlahuizcalpantecuhtli but only the first shows his characteristic face paint; the remaining four wear masks that seem to represent different day signs (Milbrath, 2013, color plate 16). Another almanac on pages 25–26 includes tonalpohualli dates that accurately predict the heliacal rise of the morning star between 1473 and 1504 (Bricker, 2001, 2010, p. 338). Recent research also emphasizes the importance of Venus in an almanac featuring the rain god on Borgia 27–28, with Calendar Round dates that can be linked with real-time astronomical events involving Venus and other planets (Aveni, 1999; Milbrath, 2013, Table 3.1). It is noteworthy that more than a quarter of the dates in the 52-year Calendar Round (Xiuhmolpilli) recorded in the Borgia may be linked to Venus events that date between 1457 and 1519 (Milbrath, 2013, Table 3.1). These include dates marking a four-part division of the synodic cycle, most notably the first and last visibility of the morning star before superior conjunction, and the first and last visibility of the evening star, followed by the brief period of inferior conjunction.

Venus plays the most important role in the narrative section on Borgia 29–46. Seler (1904–1909, 1963) explored Venus events in this narrative, but he interpreted most of the imagery in relation to the underworld sojourn of Venus during inferior conjunction. Although his interpretation has remained accessible in a 1963 Spanish translation of the original German publication, some recent interpretations have minimized the importance of astronomy in the narrative, essentially ignoring most of the Venus imagery (Anders, Jansen, & García, 1993; Boone, 2007; Byland & Pohl, 1994; Nowotny, 2005). One interpretation suggests the narrative is a mythic history of the heavens and the Earth, akin to the legends recorded in colonial period texts (Boone, 2007). Another relates the narrative to political matters and attendant ritual events (Byland & Pohl, 1994, pp. 86, 129, 152–153, 156–160; Pohl, 2004, p. 390). Nonetheless, Seler’s recognition of the important role of Venus in the narrative on Borgia 29–46 remains valid, even though his interpretations have been modified by more recent studies, including the author’s.

Cecelia Klein’s (1976, pp. 10–11; Klein, 2010, pp. 211–212) research incorporates Seler’s work but added an intriguing theory relating the imagery on Borgia 40 to the Aztec Calendar Stone (Figures 1, 2). She proposes that both show Yohualtecuhtli as the dying Sun when it reached the center of the underworld with Venus at the simultaneous completion of the 52-year solar cycle and the end of a Venus cycle during inferior conjunction. The author also links these two images to the dying Sun, but argues that they represent the death of Tonatiuh during a total solar eclipse (Milbrath, 2013, p. 123, note 18; Milbrath, 2017). This study emphasizes the relationship between Venus imagery on Borgia (page 40) and eclipse iconography, noting that Venus gods are shown attacking the blackened Sun during an eclipse event because Venus is always seen close to the Sun during a total eclipse. The Borgia narrative seems to be a dramatic recreation of celestial events coordinated with the annual cycle of festivals in a year that witnessed a total solar eclipse seen in central Mexico (August 8, 1496), the only total eclipse of the Sun documented in the annals of Aztec history (Milbrath, 2013, pp. 44–45).

Figure 2. Codex Borgia, page 40, showing Venus gods attacking the Sun during a total solar eclipse. Adapted from Milbrath (2013, Figure 3.5).

Nine different avatars of Quetzalcoatl slice open bloody Sun disks in this image of a total solar eclipse (Figure 2). The central figure leading the attack is Quetzalcoatl wearing a hummingbird costume. Another Quetzalcoatl avatar represents the wind god (Ehecatl-Quetzalcoatl) with a duck beak. Others seem to represent more obscure aspects of Venus (Milbrath, 2013, p. 43). This group of nine is the largest known assemblage of Venus gods in the Codex Borgia, helping to document the multiple manifestations of Quetzalcoatl.

The narrative on pages 29–46 is replete with astronomical events, but the primary focus is on the planet Venus and attributes associated with Venus. In the narrative Venus-Quetzalcoatl often has a smoking eye shaped like a star, which seems to be related to Venus images as a smoking star seen in the Codex Telleriano-Remensis (Quiñones Keber, 1995, pp. 235, 275). This smoking eye may also relate to imagery of comets, for the ancient Mesoamericans believed that comets originated from the planet Venus (Milbrath, 1999, pp. 250–251). Indeed, at least one image of Venus-Quetzalcoatl in the narrative can be linked with a historical sighting of a comet recorded in Chinese texts (Milbrath, 2013, pp. 81, 138–139, note 42). The positioning of Venus is also highlighted in the narrative, showing when the morning star reached maximum altitude and then began its slow descent in the east in morning sky. Paired Venus gods appear atop a pyramid when Venus was high in the sky during a 20-day veintena (on page 33) (Milbrath, 2013, plate 5). And when Venus slowly descended as the morning star on page 35, Quetzalcoatl walks down a winding path accompanied by Tezcatlipoca, here portraying the waning Moon (Milbrath, 2013, plate 7).

Figure 3. Codex Borgia, page 30: Venus as a rayed disk with Ehecatl-Quetzalcoatl surrounded by stars, representing the newly emerged morning star. Adapted from Milbrath (2013, color plate 2).

Different deities depict the transformation of Venus in the narrative, illustrating how Venus changes over the course of its synodical cycle. Page 29 shows a skeletal Venus god being burned in a jade bowl that holds the burned heart of a sacrificial victim, echoing descriptions in the Anales de Cuauhtitlán that recount how Quetzalcoatl set himself on fire and his heart was transformed into the morning star during the brief period of inferior conjunction (Milbrath, 2013, plate 1). Next Ehecatl-Quetzalcoatl is seen as the newly emerged morning star on page 30, surrounded by a Venus disk arrayed with stars depicted as the “eyes of the night” (Figure 3; Milbrath, 2013, plate 2). Another rayed disk appears when the planet is about to disappear as the morning star (page 41; Milbrath, 2013, plate 13). These two astronomical images highlight the fact that the planet is especially bright when in close proximity to the Sun, just before and after conjunction.

Venus is shown as an underworld journey on pages 42–45 during a relatively long sojourn in superior conjunction (73 days; Milbrath, 2013, p. 100). Page 42 shows the death of Quetzalcoatl at the time when Venus disappeared in superior conjunction. The underworld manifestation of Venus also is referenced in imagery of a death aspect of Tlahuizcalpantecuhtli on Borgia 45, here shown as a skeletal god merged with the hunting god, Camaxtli, while other scenes on the same page show him with his heart extracted and then decapitated, all indications that the “lord of dawn” is deceased (Milbrath, 2013, plate 17). The death of the Morning Star during superior conjunction may also evident in an Aztec myth, for when Tlahuizcalpantecuhtli failed to make the Sun move at the time of the creation of the fifth Sun, the Sun killed him with solar rays, and then the wind god, Ehecatl-Quetzalcoatl, appeared in the east to send the Sun on its course across the sky.

The concept of superior and inferior conjunction of the planet Venus was unknown to the Aztecs and other Mesoamerican cultures, including the Maya with their sophisticated astronomical records. What the Maya seemed to have focused on was the appearance and disappearance of Venus in the sky and its visibility at maximum altitude, a concept that seems to be uniquely Mesoamerican (Aveni, 2001, pp. 184–196; Bricker, 1996, p. 369; Bricker & Bricker, 2011, pp. 38–48). The Borgia narrative also seems to focus on similar events depicting Quetzalcoatl high atop a pyramid at the time Venus was at its maximum altitude on Borgia page 33, where he appears to be passing his powers to Tlahuizcalpantecuhtli, the god of the morning star (Milbrath, 2013, plate 5).

The Borgia narrative also indicates that the people of Central Mexico recognized the planet Venus as the god Quetzalcoatl, representing Venus in the morning and evening sky, but shows subtle variations to distinguish the morning and evening appearances. The postclassic Maya (AD 900–1550) also recognized Quetzalcoatl as the planet Venus, but named him Kukulcan, the Yucatec Maya equivalent of “feathered serpent.” Postclassic Maya codices show representations of Quetzalcoatl-Kukulcan, but this god is apparently a late introduction through postclassic contacts with Central Mexico (Milbrath, 1999, pp. 177–186). In addition, the Maya also recognized five different manifestations of the morning star in the Dresden Codex, comparable in some sense to the five images of Venus on Borgia 53–54, also widely recognized as a representation of the five synodical cycles of Venus, equivalent to 8 solar years (Aveni, 1999; Milbrath, 1999, pp. 163–174; Milbrath 2017, pp. 72–75, 96, color plate 16). In both codices, all five Venus gods are represented in a warlike aspect because the first appearance of the morning star was considered to be dangerous. None of these Venus manifestations is related to Quetzalcoatl-Kukulcan, but one in the Dresden Codex bears a name that is considered to be the counterpart of Tlahuizcalpantecuhtli (Milbrath, 1999, p. 173). As previously noted, Borgia pages 53–54 shows Tlauhuizcalpantecuhtli in all five scenes but four wear different masks representing day signs in the 260-day calendar.

Other Planets in the Codex Borgia

Although Xolotl is often identified as a twin of Quetzalcoatl and a canine manifestation of the evening star (Milbrath, 1999, pp. 162, 180, 186), recent study of the Codex Borgia narrative indicates that he plays the role of Mercury (Milbrath, 2013, pp. 16, 73, 94, 134, note 7). Most likely Xolotl and Quetzalcoatl are twins because both Mercury and Venus are the only planets that have a four-phase synodical cycle and both always stay close to the Sun. Just as the changing images of Quetzalcoatl track Venus over the course of its synodical cycle, Xolotl undergoes transformation as Mercury changes in position throughout the narrative. Xolotl is positioned on high up in a temple on page 37, when Mercury was at maximum altitude, and on page 38 Xolotl is seen at the end of a descending path when Mercury disappeared in the morning sky (Milbrath, 2013, plates 9, 10). Page 38 also shows Quetzalcoatl on a different path of descent alongside Xolotl when Venus and Mercury were actually descending together in the morning sky, and these paired images of Quetzalcoatl and Xolotl on Borgia 38 refer to Venus and Mercury traveling together as morning stars.

The author’s research suggests a historical framework for the events portrayed on pages 29–46, suggesting a link with central Mexican seasonal festivals and real-time astronomical events featuring Venus and Mercury in the late 15th century. This allows an understanding of the subtle changes in the imagery of these deities. Xolotl-Mercury in his underworld aspect is usually black and anthropomorphic, represented by either a skeletal avatar or a figure with the deformed body of a person who has burned to death (Borgia 38, 42), and when Mercury was invisible in conjunction with the Sun on Borgia 43, Xolotl has a canine face and wears a starry orb covered by the Sun disk (Milbrath, 2013, plate 15). Here, he also has attributes of Quetzalcoatl because both Mercury and Venus have come together in the underworld, when they were invisible in conjunction with the Sun during the period represented on this page (September 7–26, 1496).

Venus and Mercury are celestial twins because they are both inferior planets traveling on inner orbits around the Sun, but Mercury’s period of invisibility is almost equal to the period when it is visible in either the morning or evening skies, and the planet makes frequent trips to the underworld. Xolotl’s association with the nether regions is well known in mythology and his frequent trips to the underworld seem to be related to the fact that Mercury is often invisible in conjunction. Xolotl was sent to the underworld to retrieve the bones of mankind, an action sometimes attributed to Ehecatl, who retrieves the bones of the dead to create mankind (Garibay, 1973, p. 106). Likewise, Ehecatl-Quetzalcoatl’s trip to the underworld in search of bones of the dead, recounted in the Leyenda de los Soles (Bierhorst, 1992, p. 145), may represent the frequent disappearances of Venus during conjunction with the Sun.

The chronology developed from study of the veintena festivals and specific events involving the Sun, Moon, Venus, and Mercury provides an outline for a sequence that may help to identify other planetary deities. When Venus was close to Saturn at dawn in 1496, we see Quetzalcoatl with Yoaltecuhtli, a nocturnal god who may represent Saturn (page 35; Milbrath, 2013, p. 85, plate 7). Red Tezcatlipoca seems to be paired with lunar deities at times when Mars and the Moon were close together (pp. 34, 40, 41, 42). Likewise, Red Tezcatlipoca is paired with the spotted Quetzalcoatl on page 41 at a time when Mars was close to Venus (Milbrath, 2013, plate 13). Mars may also appear in a knife-headed image of the Red Tezcatlipoca on Borgia 34, an avatar of Tezcatlipoca that is clearly distinguished from the black Tezcatlipoca, a lunar god who is the companion of Venus-Quetzalcoatl as the morning star in the astronomical narrative (Milbrath, 2013, pp. 62, 84–85). Another knife-headed Tezcatlipoca, painted gray on Borgia 33, may symbolize Jupiter. The Codex Borgia seems to provide support for linking Tezcatlipoca with the Moon and one or two planets, and Tezcatlipoca seems to have so many different aspects in central Mexico that he may embody the night itself, including the stars, planets, and the Moon (Milbrath, 2013, p. 109).


Venus is clearly the most important planet in Aztec cosmology, but the other planets cannot be definitively identified. The chronicles reviewed here place the greatest emphasis on Venus in the guise of Quetzalcoatl, and the importance of this planet is also reinforced by the imagery on the Aztec Calendar Stone, where Venus images appear with the fifth Sun, Tonatiuh. The five world ages represented by the five Suns suggest these may represent the brightest “planets” (including the Sun and Moon).

Venus symbols are prominent in the eclipse event depicted on the Aztec Calendar Stone, representing the demise of the fifth Sun in an apocalyptic total eclipse (Figure 2). Venus also plays a central role in eclipse imagery in the Codex Borgia, a Tlaxcalan source that features numerous Venus events and provides an understanding of how the Aztecs may have viewed the planet in its multiple transformations. What is clear from this study of the Borgia narrative is that many different avatars of Venus are required to tell the story of Venus transitioning from morning star to evening star, represented in a section devoted to the long sojourn in the underworld during superior conjunction. Throughout the narrative, Quetzalcoatl represents Venus in all its aspects, but his image undergoes subtle transformations reflecting the synodical cycle of Venus, and in a similar fashion, Xolotl represents Mercury in all its aspects, but his image undergoes transformations to show changes over the course of Mercury’s synodical cycle. The visual imagery in the narrative corresponds closely to the positions of Venus and Mercury over the course of a year and shows changing positions of these two planets in 1496, the year of the only total solar eclipse recorded in Aztec sources.

Venus is clearly paramount in both the Aztec chronicles and the Codex Borgia, an important repository for many central Mexican beliefs that were not recorded by Spanish chronicles. The narrative remains the single most important source for our understanding of the nuanced changes in the planets Venus and Mercury. Identification of other planets in the astronomical narrative is more difficult and must remain speculative, but different-colored variants of Tezcatlipoca may represent the Moon, Mars, and Jupiter. Despite the frustration of not having adequate sources to identify planets other than Venus in Aztec chronicles, there is a wealth of information on astronomy in the Borgia narrative that helps us identify planetary gods and also enhances our understanding of Aztec myths, such as the account of Tlahuizcalpantecuhtli as the lord of dawn vanquished by the Sun’s light and Quetzalcoatl’s sacrifice and transformation into the morning star.


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