Ancient Aztec Astronomy and Astrology

Like many civilizations throughout ancient Mesoamerica (present-day Central and South America), the Aztecs assigned a special meaning to the stars and celestial bodies they observed in the night sky. The alignment of the moon, sun, planets, and constellations greatly influenced the cultural traditions and practicalities of everyday life for the Aztec people. As the civilization developed over 150 years, so did the advancements of Aztec astronomy.

Even today, many centuries later, astronomy scholars, cosmologists, and even psychics who study the zodiac rely on the discoveries of the Aztec people for the basis of research and scholarly dialogue.

Like the Mayans, the Aztecs maintained two astronomical calendars: a 365-day civil calendar and a 260-day ritual calendar. The civil calendar cycle, or xiuhpōhualli, followed the movement of the earth around the sun. As such, it was heavily relied upon for agriculture. By understanding the dates within the 365-day cycle, Aztec farmers could appropriately plan when to plant and harvest to ensure maximum agricultural production.

Although our modern civil calendar also follows a 365-day cycle, the Aztecs did not assign days to months the same way we do today. Instead, their civil calendar contained 18 months, with each month consisting of no more than 20 days. This resulted in a total of 360 named days. The remaining five days were nameless and considered to be unlucky in ancient Aztec astronomy.

Upon the start of each 20-day month, the Aztecs would hold a festival to celebrate the coming days. The assigned names of those festivals generally corresponded to specific activities or environmental conditions they could expect during that period. For example, a festival late in the spring was named Tōxcatl, which translates to “dryness.”

The Aztec 260-day ritual calendar cycle, or tōnalpōhualli, was considered just as important as the civil calendar, but was more of a sacred calendar used for divinatory purposes. This calendar assigned specific days to Aztec deities. According to the calendar, there’s a cycle of 20 named periods with 13 days assigned to each period.

By assigning gods to certain days, the Aztecs are able to keep their gods separate and allow them to reign during specific periods of time. This avoided any potential conflict and spiritual wars. The idea of equilibrium was very important to the ancient Aztecs. Without it, the world could abruptly end. This calendar was a way to ensure a constant, harmonious balance. Although not based in astrological science, the ritual calendar still held a notable and significant purpose in Aztec society.

In examining the ritual calendar, the Aztecs assigned gods to not only each of the 13 days within a period, but to each of the 20 periods as well. The gods assigned to each of the 13 days are as follows.

Day 1 – Xiuhtecuhtli: Considered the “creator of all life,” Xiuhtecuhtil is presented with a yellow or red face with a crown that includes a turquoise stone. He often appears elderly and is the central deity of the New Fire Ceremony.

Day 2 – Tlaltecuhtli: She is considered to be the “Earth Goddess.” Tlaltecuhtil is known for her pain and suffering and was often called upon to assist mothers with difficult births.

Day 3 – Chalchihuitlicue: An overseer of rivers, oceans, and bodies of water, she is often depicted wearing a jade skirt.

Day 4 – Tonatiuh: As the god of the sun, Tonatiuh is often represented with the calendrical sign. He is the symbol of the present era, where the sun reigns supreme.

Day 5 – Tlazolteotl: Associated with the moon and lunar cycle, Tlazolteotl is the goddess of sexuality and fertility. She protects midwives and fortune tellers.

Day 6 – Mictlantecuhtli: This god is commonly associated with bats, owls, and spiders. He rules over the underworld and has a notable role in many ancient Aztec fables.

Day 7 – Centeotl: He is associated with the most important agricultural product in ancient Aztec civilization: maize. His name translates to “the hairy one.”

Day 8 – Tlaloc: Known as the god of rain, Tlaloc is worshipped for the natural resource he provides. However, he is also responsible for lightning, thunder, floods, and droughts and is therefore thought to be wrathful as well.

Day 9 – Quetzalcoatl: As the patron god of priests, Quetzalcoatl is known for his wisdom and intelligence. He is the “giver of life” in all its forms.

Day 10 –Tezcatlipoca: Often depicted with white and black stripes across his face, Tezcatlipoca is the god of the night sky and embodies the evolution of humanity through conflict.

Day 11 – Chalmecatecuhtli: In Aztec lore, the underworld consists of nine separate levels. Chalmecatecuhtli rules one of those levels as the god of sacrifice.

Day 12 – Tlahuizcalpantecuhtli: As the god of conflict and war, he is often depicted with a warrior headdress and weapons in both hands.

Day 13 – Citlalicue: Along with her husband, Citlalicue created space and the stars. She is also considered to be the overseer of death and darkness.

In Ancient Aztec Astronomy, the Aztecs firmly believed that the key elements of astronomy, including the constellations and star they were comprised of, were closely tied to life and death circumstances. One example is the half-century calendrical cycle. Every 52 years, the civil and ritual calendars would overlap. To the Aztecs, this occurrence constituted a significant event as it could potentially spell doom for all of mankind.

On the day the astronomical calendars overlapped, Aztec priests would meet at midnight in a sky watcher temple located in the Aztec capital of Tenochtitlan. They would turn their eyes to the sky to observe a specific celestial phenomenon. The story goes that if the god Tezcatlipoca were to grant humankind another 52 years, he would pass the Pleiades constellation across the zenith of the sky.

Once the priests confirmed that the gods were happy and that the Aztecs would go on to live another day, the new 52-year calendar cycle would be celebrated with an elaborate festival known as the New Fire Ceremony. This festival not only celebrated perpetual life, but it also marked an important occasion to recognize the deities and celestial beings that the Aztec people placed their faith in. 

Not only were the Aztecs advanced astronomers, but they also strongly believed in astrology. The ritual calendar assigned gods not only to the 13 days within each of the 20 periods, but gods were also assigned to each period as well. Those 20 periods make up what is considered to be the Aztec form of the modern zodiac signs.

The 20 astrology signs of the Aztec calendar are: Cipactli, Ehecatl, Calli, Cuetzpalin, Coatl, Cimi, Manik, Tochtli, Atl, Itzcuintli, Ozomahtli, Malinalli, Ben, Ocelotl, Cuauhtli, Cib, Ollin, Tecpatl, Cauac, and Xochitl.

Based on an individual’s date of birth, it is possible to determine aspects of their personality and character traits based on which of the 20 astrological signs they fall into within the Aztec astrological cycle. The characteristics of the god that rules over that particular period would closely mirror those of the individual themselves.

For example, someone who is born under the period ruled by Ozomahtli places a special emphasis on their social life. They crave attention and recognition and are likely to find work in the dramatic arts as performers or actors. Just like the god Ozomahtli, they are witty and intelligent but are also often quick to engage in conflict.

While much of Ancient Aztec Astronomy and astrology remains a mystery, recent discoveries by archeologists and historians have unlocked clues that have helped us to better understand the importance of constellations and celestial bodies in Aztec life. The positions of stars and constellations not only advised the Aztecs on practical matters such as agricultural cycles, but they also carried a significant importance in Aztec culture, society, and religion.

Check out other articles from our blog for more astronomy and star facts.