Category: Astronomy | AlegsaOnline.com

Orbital plane (astronomy)

Orbital resonance

Orbital resonance: dynamics, examples, and significance

Orbital revolution

Orbital revolution: motion of planets, moons and satellites

Orbital speed

Orion

Orion (constellation)

Orion (constellation): stars, nebulae, mythology and visibility

Orion (spacecraft)

Orion Arm

Orion Arm (Local Spur) — the Solar System's region of the Milky Way

Orion complex

Orion Molecular Cloud Complex

Orion nebula

Orion Nebula (Messier 42) — nearest bright region of massive star formation

Orion's Belt

Orrery

Orrery: Mechanical models of the Solar System

Orthosie (moon)

Orthosie (moon of Jupiter)

Ōsumi (satellite)

Outer planet

Outer Planets of the Solar System

Outer space

Outer space: overview, structure, history, and importance

Owl nebula

P Cygni

P Cygni: a luminous blue variable star in Cygnus

Paaliaq (moon)

Paaliaq — an irregular moon of Saturn

Pallene (moon)

Pallene (moon of Saturn)

Palomar Observatory

Pan (moon)

Pandora (moon)

Parabolic trajectory

Parabolic Orbit: The Eccentricity-1 Boundary Between Bound and Unbound Motion

Parallax

Parallax: apparent displacement, measurement, and applications

Parallel universe

Parker Solar Probe

Parsec

Parsec: definition, measurement, and role in astronomy

Pasiphaë (moon)

Pasiphaë (Jupiter moon)

Pasiphaë group

Pasiphaë group — Jupiter’s retrograde irregular moons

Pasithee (moon)

Paul Oswald Ahnert

Paul Oswald Ahnert: German astronomer and author of the Kalender für Sternfreunde

Pavo (constellation)

Pease 1

Pease 1 — a planetary nebula in the globular cluster Messier 15

Pegasus (constellation)

Pelican nebula

Pelican Nebula (IC 5067/5070): a nearby star-forming emission region

Per aspera ad astra

Latin motto meaning 'through hardships to the stars'; history, grammar, variants, and modern uses as a symbol of striving and achievement.

Astronomy