A B C D E F G H I J K L M N O P Q R S T U V W X Y Z # Select the first letter of the word from the list above to jump to appropriate section of the glossary. If the term you are looking for starts with a digit or symbol, choose the '#' link. - P - Paleolithic Early Stone Age, roughly 40,000-12,000 years B.C.E. Demarked by hunter-gatherer societies. parallax The apparent shift of a nearby object against a more distant background, when viewed from two separeate points. parsec 3.26 light years. One parsec is the distance in which a star would have a parallax of one second of arc. passage grave Neolithic burial monuments in ancient Ireland, whose forms bore similarities to birth chambers, and may well have honored both death and re-birth. perigee The point in its orbit around the Earth at which an object is closest to the Earth. perihelion The point in the path of an object orbiting the Sun where it is closest to the Sun. petroglyph Also known as "rock art", these are prehistoric carvings into rock. In many cases, may be a form of writing. pictograph Prehistoric rock art, often of symbolic meaning. Pisces The final constellation in the Greek-based zodiac. planet Planets are large, solid, spherical masses which revolve around a star, typically in near-circular orbits. Pleiades A star cluster in Taurus, known as the Seven Sisters, although only six stars are readily visible. Pluto The ninth planet out from the Sun, it was discovered in 1930. Its eccentric orbit often takes it closer to the Sun than Neptune's. Polaris Currently the North Star, it is the final star at the handle of the Little Dipper. Back to Top - Q - (empty) Back to Top