The oldest solar observatory of the American continent discovered

Towers of the Chankillo Citadel in Peru mark the position of the sun

Sunrise between Tower 1 and Cerro Mucho Malo. © Ivan Ghezzi
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Archaeologists have discovered Peru's oldest solar observatory on the American continent. As they report in the journal "Science", the battlements of the citadel in Chankillo coincide exactly with the sun positions at certain times of the solar year.

Chankillo is a multi-square kilometer ceremonial facility in the coastal desert of Peru. Built in the fourth century BC, the site crowns a fortified, 300-meter long structure on the crest of a hill with 13 towers, locked gates and battlements. Archaeologists have been controversial for years about whether this structure is a fort or has a ceremonial meaning. Now archaeologists from Yale University and the University of Leicester have clarified this issue. The scientists around Ivan Ghezzi could prove by surveying and comparing with historical texts clearly that the structure must have served as a solar observatory.

"Sun pillar" on the horizon

"For decades we have known from archaeological artifacts and documents that the Incas operate a so-called 'solar horizon astronomy', " explains Ghezzi. "She uses the positions of the rising and setting sun to determine the season. We knew that the Inca astronomy was already well advanced and that they used buildings as a kind of landmarks to determine the sun's position on key data of the year. "

According to archival texts, "sun pillars" were used on the horizon near Cusco to plan planting times and festivals, but these pillars have disappeared and their position remains unknown. Now researchers have first discovered tangible examples of such pillars. Already in 2001 Ghezzi had noticed the positions of the 13 towers of the citadel in Chankillo. "Since the 19th century, there is already speculation that the arrangement of the 13 towers could have had an astronomical function, but no one pursued this, " said the researcher. "So we said, now we're investigating that."

Simplified diagram of how the solar observatory works. Ivan Ghezzi

Towers mark the position of the sun

To their great surprise, the first surveys showed that one tower was aimed exactly at the position of the sun for the summer solstice, another for the winter solstice. However, it was only after many more surveys and years of field work that the scientists were able to clearly prove that this was not a coincidence, but a consequence of a deliberately planned observatory structure. display

Chankillo provides a complete set of horizon markers the 13 towers and two unique and unique observatory points, explains Clive Ruggles, a leading expert in the field of Observ Solar astronomy from the University of Leicester. The fact that the towers mark exactly the slopes of the rising and falling sun from these two points provides the clearest indication that they actually exist were built to track the sun during the year.

Chankillo Citadel. Peru's National Aerophotographic Service (SAN)

With this realization, the observatory is at the same time the oldest that has ever been discovered on the American continent. The 2, 300-year-old solar observatory in Chankillo is the oldest structure of its kind. Unlike all other observatories, it contains structures that cover the entire solar year, Ghezzi says. It is even 500 years older than Mayan monuments erected for similar purposes in Central America.

(Yale University, 02.03.2007 - NPO)