P
- Parabola
- Parkes 64 metre radio telescope
- Parsec
- Peculiar Velocity
- Periapsis
- Periastron
- Perigee
- Perihelion
- Period
- Period Derivative
- Phases
- Photodisintegration
- Photon
- Photosphere
- Pierre Auger Observatory
- Planck Energy
- Planck Length
- Planck Mass
- Planck Temperature
- Planck Time
- Planck Units
- Planck's Constant
- Planet
- Planetary Nebulae
- Planetesimals
- Plutinos
- Population I
- Population II
- Population III
- Positron
- Potentially Hazardous Asteroids
- Power Spectrum
- Pressure
- Primordial Fireball
- Projected Semi-major Axis
- Proper motion
- Proto-planetary nebulae
- Proton
- Protostar
- PSR J0437-4715
- PSR J1141-6545
- Pulsar
- Pulsar Characteristic Age
- Pulsar Dispersion Measure
- Pulsar Evolution