Sirius B Star Logo

The brightest star in the night sky, Sirius is recorded in some of the earliest astronomical records. Its displacement from the ecliptic causes its heliacal rising to be remarkably regular compared to other stars, with a period of almost exactly 365. 25 days holding it constant relative to the solar year. This rising occurs at Cairo on 19 July (Julian), placing it just prior to the onset of the annual flooding of the Nile during antiquity. Owing to the flood’s own irregularity, the extreme precision of the star’s return made it important to the ancient Egyptians, who worshipped it as the goddess Sopdet (Ancient Egyptian: Spdt, “Triangle”;[a]Greek: Σῶθις, Sō̂this), guarantor of the fertility of their land. [b] The Egyptian civil calendar was apparently initiated to have its New Year “Mesori” coincide with the appearance of Sirius, although its lack of leap years meant that this congruence only held for four years until its date began to wander backwards through the months. The Egyptians continued to note the times of Sirius’s annual return, which may have led them to the discovery of the 1460-year Sothic cycle and influenced the development of the Julian and Alexandrian calendars.