Incan Astronomy: A Brief and Personal Journey  

For centuries and through a handful of civilizations, the Andean people have cultivated a worldview and way of living as unique as the lands they inhabit. While the Constellations seen from Europe and North America are rooted in the classical Greek and Babylonian traditions (think Centaur and Orion), the Southern Constellations are a group of 32 “newer” star arrangements whose names rely heavily on imagery of navigation and exploration (think Compass and Sea Serpent). Despite the relative recency with which these Southern patches of sky were defined and formally named, their shining presences were of utmost significance to Incan and pre-Incan societies (the oldest dating back to 3,200 BCE). The last chapter and largest pre-Columbian empire were the Incas–a patchwork empire of language, culture, landscape, and people. Cusco was their capital, what they referred to as the “bellybutton of the universe.” High up in the Andes, they ruled an enormous portion of the western part of South America for about 100 years from roughly 1483 to 1533 and created massive administrative and governing infrastructures, buildings, and roads.

All ancient cultures practiced mythmaking and classification in order to understand the cycles of nature and organize their worlds, but to me the Incas are the most fascinating.  Their large and crumbling Sun Temples are places of immense intrigue. Their worship, rituals, and archaeoastronomy are compelling narratives of vast intellect shrouded in a jungle-thick fog of mystery. They had no written language but profoundly understood that the usage and interpretations of the sky was necessary to their survival. To the Incans, astronomy was a way to understand the world and their place in it. In a recent trip to Peru I got to make my own course through their complex grappling of the heavens. They read the skies like a manual, one I became intent on learning as much about as possible.


Upon arriving in Cusco, I spent the evening learning about Peru’s sky at the Cusco Planetarium. Here, with the assistance of telescopes, binoculars, and extremely enthusiastic and knowledgeable hosts, we were given an overview of the tenets of Incan Astronomy and its context to life in the Andes. A planetarium presentation provided a primer of the Southern Constellations and the Incan conception of the Milky Way. Outside, as the night sky grew dark and cloudless, we were treated to a viewing of three Galilean moons of Jupiter (and Jupiter!), an open cluster in the tail of Scorpio, and the Jewel Box cluster in the constellation Crux. It was a spectacular night of stargazing and education that formed a foundation for the cultural and archaeological astronomy I would experience later on.

The skies were read symbolically, as a part of their rituals and as a means to predict the future. To understand how and why the Incans interpreted the skies as such, we have to establish the lens through which they understood their existence. In Incan mythology, there are three different levels of “worlds”:

  • Hanan pacha, the “upper” physical and metaphysical realm of the sky, planets, stars, sun, and moon, but also where other gods, such as the god of thunder all exist
  • Kay pacha, the “middle” earthly realm of plants, humans, and animals
  • Uku pacha, the “inner” world, where the dead, new life, demons, and Pachamama, the earth goddess, live.

This cosmological triptych is connected in myriad ways, be it through a mountaintop altar connecting Kay pacha to Hanan pacha or a cave joining Uku pacha to our middle world.

The sky was a reflection of their earthly existence. The Milky Way, Mayu, was considered a river bridge to their version of a world after death, mimicking their sacred mountainous one – Vilcanota. Here in the dark cloud constellations of their cosmic river they saw familiar animals: mother and child llamas, partridges, and toads, among others. These dark cloud creatures were not inanimate but leapt out of the sky according to mythology and behaved in ways up there that became predictors of natural events down here, like how the haziness or clarity of the mother llama constellation during certain parts of the year would forecast rainy or dry seasons. Through observation they learned of the seasons and other cycles, and they established a calendar that propelled their civilization towards becoming more agrarian and less nomadic. Priest-astronomers translated the heavens in order to manage the natural world, using, for example, the heliacal rising of the Pleiades to signal the sowing season, because to them their in their eyes the stars’ resemblance was to neither a sail nor a myth of fleeing sisters but rather to a pile of seeds. They had learned to conquer time.

The sky was where their main gods lived. The sun, Inti, was their main deity and a father of their ruler the Inka. In addition to the sun, they worshipped the moon, planets, and stars, depicting their importance in religious relics through the use of gold, silver, and precious stones. They referenced the phases of the moon to further dictate their harvesting and planting schedules, and they used bright, full moon nights to conduct lunar rituals. They referred to the moon as Mother Moon, Mama Killa, and would not fight battles at night out of respect for her.

For rituals and worship, the most important days were the two solstices. Believing the Inka had control over the actions of the sun, huge celebrations on June 21 (winter) and December 22 (summer) solstice days cemented the belief that the duration of daylight was at the command of one person, their leader. The cultural importance of these days and subsequent celebrations resisted Spanish colonization and remain contemporary strongholds.


The interconnectedness of their beliefs was never clearer than through the ruins. These physical spaces offer a much greater grasp on their abstract theory. Gazing up at the stars and finding new or known constellations was only a part of my journey, and a walk through Machu Picchu was seminal to my nascent understanding.

Touted as a royal summer palace, trading hub, or a nunnery for chosen women, the secrets of this site leave all puzzled. Built in a strategic location nestled in the middle of important mountain peaks and encircled by a sacred river, Machu Picchu was primed for documenting the heavens. Even though much is unknown about this refuge, the architecture – passageways, windows, altars, and temples – provides clues to precise elements built for and around witnessing astronomical events.

Machu Picchu’s Temple of the Sun (an arbitrary name given by Hiram Bingham, the 1911 explorer who stumbled upon this abandoned town and catapulted it into its international renown) is a three-level “tower” that brought everything I had learned in my months of research to a realization. The temple’s upper portion served as an observatory with three windows on a curved wall facing east. Here priests would watch and track movements of celestial bodies at day and night and look up at the Milky Way. The second level is a cave-like nook built on the existing granite mountainside that contains a small altar used by priests. Depending on the story told from up above, sacrifices or different rituals would be performed. The lower level, a quasi –mausoleum housed the mummies of their ancestors. They practiced ancestor worship and mummified their dead to preserve them, believing they would return to the “middle” world of the living after spending time in the “upper” world. Next to this one structure, surrounded by a cacophony of foreign languages and under a furious sun in a cloudless azure sky, I was struck by the meaning and cohesion – the fullness of it all.


Lured to these highlands by an ancient trail, I spent 4 days trekking up and down mountains that concluded at the emerald hills of Machu Picchu. During the arduous walking I spent a lot of time resting and thinking about the people who built these trails and buildings, who walked these lands, who believed unequivocally in the sky to guide them along. In preparation for my trip, I tried to read loads on Incan astronomy, about their history and culture, but I still found myself stunned at their ingenuity, astuteness.

On the first night, at camp along the trail, I was utterly unprepared and gob smacked in the middle of an empty field gazing up at the Milky Way. Sandwiched between skyscraper mountains and Incan ruins, and beneath the blazing swatches of black and deep purple, I stood reverent below the Southern Cross. Under the watchful, wise gaze of the mother llama eyes – Alpha and Beta Centauri – I thought of the millions who came before me that looked up as well, probably in a similar state of awe, asking the same internal questions, and squinting, scanning the sky for answers.