M numbers;System for the classification of galaxies developed by Charles Messier (1730-1817).
Magnetic field;Area that is affected by the magnetic forces of a planet.
Magnetosphere;Area that is affected by the magnetic forces of a planet.
Magnitude;Term describing the brightness of a star.
Main sequence;Diagonal zone of the Hertzsprung-Russell diagram, where more than 90% of all observable stars are located.
Main sequence star;Star that is located within the clearly defined diagonal section of the Hertzsprung-Russell diagram.
Mantle;Rock layer between the core and crust of a satellite or solid planet.
Mass;Total of matter contained in a body.
Matter;Atomic particles, and substances consisting of atoms and molecules in the universe.
Meridian;Imaginary circle in the celestial sphere through the celestial north pole and south pole as well as the point directly above the observer.
Messier catalogue;Catalogue comprising more than 100 nebulae and star clusters, first published by Messier in 1784.
Meteorite;A meteor that is not entirely consumed in the atmosphere and reaches the surface of the Earth.
Meteors;Small solid bodies entering the Earth's atmosphere and raised to incandescence by the friction with atmospheric particles.
Methane;Gas produced in decomposition processes of organic matter.
Milky Way;Hazy belt of stars extending across the sky. It consists of the combined light of millions of stars.
Milky Way system;Name of our star system, also referred to as a galaxy.
Molecule;Chemical compound of two or more atoms.
Month;Period in which the Moon completes a full revolution about the Earth.
Moon;Natural satellite of the Earth. Also, satellites of other planets.
Motion;Movement of a celestial body in the same direction as the movement of the Earth, i.e. from left to right.
Mounting;System that carries a telescope.
NASA;Abbreviation for National Aeronautics and Space Administration, US-space research agency
Navigation;Guidance of a vehicle or vessel to its destination, including all calculations for the determination of the current position.
Nebula;Cloud of gas and dust, often containing a mass that corresponds to several million times the mass of the Sun.
Neutrino;Elementary particle, released during nuclear fusion reactions.
Neutron;Uncharged fundamental particle with a weight that is marginally greater than that of a proton.
Neutron star;Core of a star of extremely high density, which is left over after a supernova explosion.
Newton;Newton, Isaac, 1642-1727, British scientist.
NGC;New General Catalogue: catalogue of star clusters, nebulae and galaxies compiled by Herschel and Dreyer in 1889.
NGC number;Classification number of the New General Catalogue of Nebulae, and Clusters of Stars.
Night shadow;Shadow on the side of the Earth that is not facing the Sun.
Nova;Star that suddenly appears with great luminosity in the sky and subsequently returns to its original magnitude.
Nuclear fusion;Nuclei of light elements fuse to form a heavier nucleus. Energy is released in the process.
Nucleus;Area around the center of a planet, star or galaxy.