Did the ancient egyptians record the period of the eclipsing binary Algol - the Raging one?

TL;DR

This paper suggests that ancient Egyptian records in the Cairo Calendar may contain the earliest known documentation of the eclipsing binary star Algol's period, predating modern observations by three millennia.

Contribution

It provides evidence that ancient Egyptians recorded the variable star Algol's period, potentially making Cairo Calendar the oldest historical record of a variable star.

Findings

Ancient Egyptians recorded Algol's period as 2.850 days.

The Cairo Calendar may be the earliest record of a variable star.

Period changes in Algol are linked to historical documentation.

Abstract

The eclipses in binary stars give precise information of orbital period changes. Goodricke discovered the 2.867 days period in the eclipses of Algol in the year 1783. The irregular orbital period changes of this longest known eclipsing binary continue to puzzle astronomers. The mass transfer between the two members of this binary should cause a long-term increase of the orbital period, but observations over two centuries have not confirmed this effect. Here, we present evidence indicating that the period of Algol was 2.850 days three millenia ago. For religious reasons, the ancient Egyptians have recorded this period into the Cairo Calendar, which describes the repetitive changes of the Raging one. Cairo Calendar may be the oldest preserved historical document of the discovery of a variable star.