A second star would have added to the effect, Magli said. The "King's Star" Regulus, which is found on the head of the lion in the constellation Leo, also rose in near-perfect alignment with Canopic Road and became visible after a period of conjunction with the sun near July 20. Earth's orbit has changed enough that this Regulus phenomenon no longer happens, Magli said.
Sun as a symbol
Architecture-by-astronomy was common in the ancient world, Magli said. The Great Pyramid of Giza, for example, is aligned with amazing precision along the compass points, which would have required the use of the stars as reference points. The Egyptians, whom Alexander conquered, had long associated the sun god Ra with their pharaohs.
"Aligning the city (of Alexandria) to the sun in the day of birth of Alexander was a way to embody in the architectural project an explicit reference to his power," Magli said. The King's Star would have only added to the mystique, he said.
The researchers reported their work online Oct. 9 in the Oxford Journal of Archaeology. They are now examining other cities founded by Alexander and later rulers to see if the solar pattern holds. The hope, Magli said, is that an understanding of Alexandria's astronomical layout will give researchers a better idea of where Alexander's tomb might be.