All
- Metals
- Meteor
- Meteor Shower
- Meteor Stream
- Meteorite
- Meteoroid
- Micrometeorite
- Milky Way
- Millisecond Pulsar
- Mirror
- Molecular Cloud
- Molecular Hydrogen
- Molecule
- Moment of Inertia
- Momentum
- Monolithic Collapse
- Moon
- Mopra Telescope
- Morgan-Keenan Luminosity Class
- Morphological Peculiarities
- Morphology Density Relation
- Nadir
- Narrowband
- Near Earth Asteroids
- Nebula
- Neutral Hydrogen
- Neutron
- Neutron Star
- New Moon
- Newton's First Law of Motion
- Newton's Second Law of Motion
- Newton's Third Law of Motion
- NGC
- Non-thermal Radiation
- North Galactic Pole
- Novae
- Nucleosynthesis
- Nyquist Rate
- Objective Lens
- Oort Cloud
- Opposition
- Orbit
- Orbital Eccentricity
- Orbital Elements
- Orbital Inclination