Oldest Solar Observatory in Americas Found in Peru

Archeologists may have uncovered what they say is by far the oldest astronomical observatory in the Americas: a series of towers near a temple in coastal Peru, built in the fourth century B.C.

The towers at Chankillo mark the sun's progress across the sky, according to a new study in Science. This suggests the sun may have played an important role in religious and political life long before the appearance of the famous Inca sun cult.

Mysterious Towers

In the 19th century, explorers in the area observed the 13 stubby towers dotting a long ridge close to an ancient fortress. The explorers suggested that the towers had to do with the movement of the moon, and left it at that.

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A few years ago, Ivan Ghezzi at long last drummed up enough funding to excavate the Chankillo site, and uncover its secrets.

Ghezzi is at the Catholic University of Peru and the national director of archeology. He quickly realized the towers had nothing to do with the moon, but everything to do with the sun. The key was viewing the sky from either of two structures that stood nearby.

"You could actually watch the sunrise align with the northernmost tower during the June solstice," he says. "And with the opposite tower... you could see the sunrise at the December solstice. So we realized that here we had an astronomical device that was designed to keep track of the movement of the sun and therefore keep track of time."

Built 2,300 years ago, the towers are by far the earliest example of an observatory in the Americas.

Sun Worshipers

Ghezzi knows frustratingly little about the people who built the towers and the fortifications at Chankillo.

It is unclear whether they were in any way forerunners of the Incas, the famous sun worshipers who appeared on the scene many centuries after these structures were built.

"We know that the Incas made powerful political statements based on the relationship between the sun and the king," Ghezzi says. "The Inca claimed to be the offspring of the sun. But now we have a society that is 1,800 years before the Inca that is clearly using the sun as a way to make a political, social and ideological statement."

It is clear that the towers were more than just a fancy sundial. For one thing, the fortifications nearby appear to protect a temple.

Anthony Aveni, an archeoastronomer at Colgate University, agrees with Ghezzi's interpretation that the site is of great cultural, religious and political significance, in addition to its practical use for timing plantings and harvests.

The priests who controlled the temple would have used their knowledge of astronomy as part of their mystique and power.

Ancient Astronomy

The question, as always in a situation like this, is whether the towers were really built with an astronomical purpose, or if the layout turns out to be a happy coincidence. Aveni, for one, is convinced this observatory was designed to track solar events.

"It does work, and it works in a way that makes sense given what we know about Andean calendars," he says.

The towers also help mark other solar events and count out a 10-day week used by Andean cultures.

Ivan Gehzzi is working to turn the well-preserved ruins of Chankillo into a major tourist destination.

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