These circumpolar stars are now known as Kochab (Beta Ursae Minoris), in the bowl of Ursa Minor or, the Little Dipper, and Mizar (Zeta Ursae Majoris), in Ursa Major, at the middle of the handle of the Big Dipper. Egyptologist Toby Wilkinson explained the naming as apt metaphor in Egyptian ideology. "Circumpolar stars are a very good metaphor for the afterlife because when viewed, they never seem to set: they simply rotate around the pole star. They are the undying stars, or in Egyptian terminology, the Indestructibles, a perfect destination for the soul of the dead king," he said in 2001. The context for this is the Egyptian belief that Ra (the sun god) was given birth to by Nut (the sky goddess). Nut was pictured as a naked female spread across the sky, and identified with the Milky Way – the legs formed by the bifurcation at Deneb in Cygnus, and the head by the swelling at Gemini. The head of Nut passes below the horizon about 75 minutes after the sun on the spring equinox, and at the same point on the horizon, "consuming" Ra, who was symbolically reborn 272 days later on the morning of the Winter solstice, on the same declination as Deneb. About 4,500 years ago, the Egyptians believed that the unmovable area the stars encircled by 10 degrees each, was heaven in the sense that it was the place of the afterlife. The pole star at the time was Thuban (Alpha Draconis). Egyptians associated those two stars with eternity and the afterlife of a king or pharaoh so that after death, a pharaoh would hope to join those stars. During the Old Kingdom it was thought that only the pharaoh and his family could ascend to heaven. As Pharaohs were buried in pyramids there were implications for their afterlife and their immortality and consequently the structures were deliberately aligned astronomically. Believing that their kings became stars in the Northern sky after death, Egyptians aligned their pyramids and temples due north toward the "indestructible" stars, giving the departed pharaohs direct access to the northern sky. As the Egyptians believed that the unmovable area the stars circled was heaven, the pyramids were built to align north with a single, perfectly aligned vent. In King Khufu's Pyramid, the shaft itself, built into the structure, started at the chamber of King Khufu and ends at the outside.