PA Painter's Easel palimpsest Pallas pallasite Palomar Observatory Palomar Sky Survey palus Pan Pandora parabola parabolic mirror parallax Paranal Observatory parent body parhelion Paris Observatory Parkes Observatory parsec particle horizon Pasiphae patera Patientia Paul-Baker system Paul Wild Observatory Pavo Pavonis Mons pc P Cygni Peacock(1) Peacock(2) peculiar galaxy peculiar motion(1) peculiar motion(2) peculiar star Pegasus Pele Pelican Nebula penumbra(1) penumbra(2) PEP perfect cosmological principle periastron pericentre perigee perihelion perihelion distance period periodic comet period-luminosity relation Perseids Perseus Perseus Arm personal equation perturbation Petavius Phaethon phase phase angle phase defect phase integral Phekda Phobos(1) Phobos(2) Phocaea group Phoebe Phoenix Pholus photoelectric photoelectric photometry photographic magnitude photographic zenith tube photo-ionization photometry photomultiplier photon photosphere photovisual magnitude Pic du Midi Observatory Pico Pictor pincushion distortion Pinwheel Galaxy Pioneer Pioneer Venus Pisces Piscis Austrinus Piton pixel plage Planck era Planck length Planck's constant Planck Surveyor Planck time planet planetarium planetary nebula planetary rings Planet-B planetesimal planetographic coordinates planetoid planetology Planet X planisphere planitia planum Plaskett's Star plasma plasmasphere plasma tail Platonic year Pleiades Pleione plerion Plössl eyepiece Plough plume eruption Plutino Pluto Pogson's ratio Pointers polar polar axis polar cap polar distance polarimetry Polaris polarization polarizer polar motion Pole Star Pollux Poop Population I Population II pore Porrima Porro prism Portia position angle Poynting-Robertson effect Praesepe preceding precession pre-main-sequence star primary mirror prime focus prime meridian primeval atom primeval fireball Principia prismatic astrolabe Procyon prograde Project Ozma Prometheus(1) Prometheus(2) prominence promontorium proper motion proplyd proportional counter Proteus protogalaxy proton-proton chain protoplanet protostar Proxima Centauri Przybylski's Star Psyche Ptolemaeus Ptolemaic system Ptolemy's rules P-type asteroid Puck Pulkovo Observatory pulsar pulsating star pulse nulling Pump Puppis Purkinje effect Purple Mountain Observatory pyrheliometer Pythagoras Pyxis PZT