The Origins of the Pentagram and Hexagram
Because Venus and Earth take different times to complete their orbits, it is 8 years before the two planets arrive back at the same initial point.

Pentacles and Pentagrams
Upright pentacles and pentagrams are among the most widely used religious symbols. They have been used in many eras and by many cultures and religions of the world.

Some say the pentagram is mystical because 5 is mystical. It's a prime number, the sum of 2 and 3, as well as of 1 and 4.

Pentagram - from Wolfram MathWorld
A pagan religious symbol that is one of the oldest symbols on Earth and is known to have been used as early as 4000 years B.C. It represents the "sacred feminine" or "divine goddess".

The Pentagram
The pentagram (also called pentacle, pentalpha, pentancle, pentagle, or pentangle) is thought by some occultists to trace its esoteric significance to an astronomical observance of the pattern of Venus' conjunctions with the Sun and has had many meanings in many cultures through the ages.

The Pythagorean Pentacle
The pentagram and hexagram were both used for protection in ancient Greece (V cent. BCE). In Babylon, five-, six- and seven-rayed stars were all used. The pentagram appears in the earliest writing of Mesopotamia (precuneiform pictographic writing), c. 3000 BCE, as the Sumerian sign UB.

Symbol 27:21 -
The pentagram or pentacle belongs to the group of some 20 basic gestalts in Western ideography.