Oldest solar observatory in Americas discovered in Peru

The oldest solar observatory in the Americas has been discovered in coastal Peru, archeologists announced today. The 2,300-year-old ceremonial complex featured the Towers of Chankillo, 13 towers running north to south along a low ridge and spread across 980 feet (300 meters) to form a toothed horizon that was used for solar observations. [See aerial photo here.]

Researchers excavated the solar observatory between 2000 and 2003. They found buildings-in exact mirror position of each other-to the east and west of the towers with observation points for watching the Sun rise and set over the toothed horizon...

As viewed from the two observing points of Chankillo, the spread of towers along the horizon corresponds very closely to the range of movement of the rising and setting positions of the Sun over the year, the authors write in the March 2 issue of the journal Science.

Once the Sun started to move away from any of its extreme positions, like the solstices or equinoxes, the towers and gaps between them provided a means to track the progress of the Sun up and down the horizon, to within a couple of days accuracy.

'Chankillo is arguably the oldest solar calendar that can be identified as such with confidence within the Americas,' said lead study author Ivan Ghezzi from Pontificia Universidad Catolica del Peru.

Tree-ring samples dated these structures back to the fourth century B.C.