"It happens at about the same time every solar year, so it corresponds to the seasons, and it provides them a good fixed date," he said.
Hammergren agrees with the days Nur El-Din's team calculated for Sothis, based on other researchers' estimates for the dates the star would have risen during ancient Egyptian times.
Still, Hammergren noted, the "appearance" of the star is subject to weather conditions, which might have obscured its first rise in any given year.
Mahmoud Afifi, the general director of Giza antiquities, is also concerned about placing an exact year on the start of Khufu's rule.
Ancient Egyptian chronology reset to zero at the beginning of each pharaoh's reign, making it difficult to match Western calendar years with the dates given for ancient events.
What's more, dated lists of kings are unreliable, since the ancient Egyptians often had political motivations to alter the historical record.
Some unpopular pharaohs could have been left off the lists, for example, which would have changed the ruling dates of every pharaoh that followed.
Many scholars debate the precise year Khufu ascended to the throne, with some estimates as much as 139 years earlier than the date Nur El-Din and his team selected.
In addition, the design of the monumental Great Pyramid probably took considerable time to prepare, Afifi said, which might have delayed the start of construction beyond the first year of Khufu's reign.
For Afifi, many aspects of the Great Pyramid simply remain shrouded in mystery. (Explore an Egyptian pyramids interactive.)
"We don't even know why [Khufu] chose the Giza plateau for his tomb, when his father was in Dashur, 30 kilometers [18.6 miles] away," he said.
"There're a lot of theories about the Great Pyramid, because it is the last [surviving ancient] wonder of the world."
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