5th/6 periods of the Period of Egyptian Image Time-identity is the Period of Sirius Disappearance and Rising covering the Annual Reports of the period of time of BC AYN 7237 through BC AYN 7018.
The heliacal rising of Sirius, by far the brightest star in the sky, known as Sopdet to the Egyptians and Sothis to the Ancient Greeks, took on particular significance as it occurred just before the seasonal flooding of the Nile. It became associated with Isis, goddess of rebirth, rising just after the constellation of Orion, associated with Osiris, god of the underworld, reborn through the agency of Isis, his consort. Both straddle the Milky Way, symbol of the life generating Nile, fed by the tears of a grieving Isis. The temples of Isis in Philae and Hathor in Dendera are both believed to have been oriented in line with the heliacal rising of Sirius. The 70 day period during which Sirius disappeared from the night sky before its heliacal rising again was also the period of time between mummification and entombment, when through the ceremony of the opening of the mouth, the dead person was believed to reawake to eternal life in the underworld.
The date of the helical rising of Sirius was taken as the beginning of the Egyptian calendar on the first day of Thoth, but because of the discrepancy between the civil calendar and the Earth’s orbit with respect to the sun and stars, this moment tracked back through the calendar in a cycle of 1461 years called the Sothic cycle. A moment when it synchronized with the civil calendar was recorded in 139 CE, which acts as a fixed point to anchor the chronology of Ancient Egypt; tracking back we can calculate that other synchronizations must have occurred in 1332 BCE and 2782 BCE.