Algol, also known as the Demon Star, is a binary system, meaning it contains two stars rotating around each other. Until recently, it was believed this unique feature was discovered by John Goodricke in 1783. Now, we have reason to believe it was detected thousands of years earlier. Did ancient Egyptian astronomers discover and understand Algol?
Algol and the Mysterious Cairo Calendar?
In 1200 BC, ancient Egyptian astronomers created a document now known as the Cairo Calendar. They used it to record observations about the sky. Recently, a team of scholars from the University of Helsinki took a closer look at this calendar. In doing so, they discovered the ancient Egyptians weren’t just recording changes in the sky. They were attempting to understand and calculate how the stars worked.
The Cairo Calendar charts at least two specific cycles. One cycle lasts 29.6 days, roughly the same amount of time as the lunar cycle. The other cycle lasts 2.85 days and appears to match the activity of Algol. Currently, Algol dims every 2.867 days, most likely because its stars rotate and block each other’s light.
Guerrilla Explorer’s Analysis
But what about that small difference between the two numbers? One possibility is the ancient Egyptians simply made slight errors in their calculations. However, there’s also an intriguing alternative theory. It’s possible Algol’s rotation has slowed over time. If this is the case, it would add evidence to a recent theory that Algol is actually a three-star system.
Interesting huh? Of course, it’s impossible to say for certain, not without a better understanding of how the ancient Egyptians recorded the cycles. Still, at least for the moment, it seems possible that the work of these ancient Egyptian astronomers has shed new light on one of the night sky’s most perplexing puzzles.