A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

M series (Japanese rockets)
M star
M1 (NGC 1952, Crab Nebula)
M2 (NGC 7089, globular cluster)
M3 (NGC 5272, globular cluster)
M4 (NGC 6121, globular cluster)
M5 (NGC 5904, globular cluster)
M6 (NGC 6405, Butterfly Cluster)
M7 (NGC 6475, Ptolemy's Cluster)
M8 (NGC 6523, Lagoon Nebula)
M11 (NGC 6705, Wild Duck Cluster)
M13 (NGC 6205, Great Cluster in Hercules)
M16 (NGC 6611, open cluster)
M17 (NGC 6618, Omega Nebula)
M20 (NGC 6514, Trifid Nebula)
M27 (NGC 6853, Dumbbell Nebula)
M31 (NGC 224, Andromeda Galaxy)
M32 (NGC 221, companion to M31)
M33 (NGC 598, Triangulum Galaxy)
M36 (NGC 1960, open cluster)
M37 (NGC 2099, open cluster)
M38 (NGC 1912, open cluster)
M41 (NGC 2287, open cluster)
M42 (NGC 1976, Orion Nebula)
M44 (NGC 2632, Praesepe)
M45 (Pleiades)
M50 (NGC 2323)
M51 (NGC 5194, Whirlpool Galaxy)
M52 (NGC 7654, open cluster)
M57 (NGC 6720, Ring Nebula)
M63 (NGC 5055, Sunflower Galaxy)
M64 (NGC 4826, Black Eye Galaxy)
M72 (NGC 6981, globular cluster)
M74 (NGC 628, spiral galaxy)
M76 (NGC 650, Little Dumbbell Nebula)
M80 (NGC 6093, globular cluster)
M81 (NGC 3031, spiral galaxy)
M82 (NGC 3034, companion to M81)
M87 (NGC 4486, elliptical galaxy)
M89 (NGC 4552, elliptical galaxy)
M94 (NGC 4736, spiral galaxy)
M95 (NGC 3351, barred spiral)
M97 (NGC 3587, Owl Nebula)
M101 (NGC 5457, spiral galaxy)
M103 (NGC 581, open cluster)
M104 (NGC 4594, Sombrero Galaxy)
M110 (NGC 205, companion to M31)
M-2 (lifting body)
M2P2 (Mini-Magnetospheric Plasma Propulsion)
maar
MABES (Magnetic Bearing Satellite)
Mach, Ernst (1838–1916)
Mach angle
Mach number
machine
machine tools
Mach's principle
MACHOs
Macintosh, Charles (1766–1843)
Maclaurin, Colin (1698–1746)
Maclaurin trisectrix
Macleod, John James Richard (1876–1935)
MacMahon, Percy Alexander (1854–1929)
MacMahon squares
McMillan, Edwin Mattison (1907–1991)
macromolecule
MACSAT (Multiple Access Communications Satellite)
macula
Mädler, Johann Heinrich von (1794–1874)
Maestlin, Michael (1550–1631)
Maffei 1 Group
Magdeburg Project
Magellan (Venus probe)
Magellan Telescopes
Magellanic Clouds
Magendie, François (1783–1855)
maghemite
magic number
magic square
maglev
magma
magnesite
magnesium
magnet
magnetar
magnetic bottle
magnetic cataclysmic variable
magnetic declination and inclination
magnetic field
magnetic field reversal
magnetic field strength
magnetic flux
magnetic flux density
magnetic levitation launch-assist
magnetic moment
magnetic monopole
magnetic quantum number
magnetic resonance imaging (MRI)
magnetic susceptibility
magnetism
magnetite
magneto
magnetogram
magnetohydrodynamics
magnetometer
magnetopause
magnetoplasmadynamic thruster
magnetosheath
magnetosphere
magnetotactic bacteria
magnetotail
magnetron
magnification
magnifying glass
magnitude
Magsat (Magnetic Field Satellite)
Maia (20 Tauri)
Maiman, Theodore Harold (1927–2007)
main asteroid belt
main sequence
Makarov, Oleg G. (1933–2003)
Maksutov telescope
malachite
malaria
male reproductive accessory glands
male reproductive duct system
male reproductive system
Malebranche, Nicolas (1638–1715)
Malfatti circles
malic acid
Malin-1
Malina, Frank J. (1912–1981)
malleability
Malmquist effect
malnutrition
Malpighi, Marcello (1628–1694)
Malpighian layer
malt
Malthus, Thomas Robert (1766–1834)
maltose
Malus, Étienne Louis (1775–1812)
Malyutka
mammal
mammary glands
mammals in the Cenozoic
mancala
Mandelbrot, Benoît B. (1924–2010)
Mandelbrot set
mandible
mandibular nerve
mandrake
manganese
manganese nodules
manganese star
manganite
Manhattan Project
Manhigh, Project
manifold
Maniitsoq impact crater
Manned Maneuvering Unit (MMU)
Manned Orbiting Laboratory (MOL)
MANNED SPACEFLIGHT
manometer
Mantell, Captain Thomas F. (1922–1948)
mantle
many-body problem
many-worlds theory
map
MAP (Microwave Anisotropy Probe)
mapping
marble
marcasite
Marconi, Guglielmo (1874–1937)
Marcus, Rudolph A. (1923–1937)
Marcy, Geoffrey W. (1954–)
MARECS
Marfan syndrome
Margulis, Lynn (1938–2011)
maria
Maria family (of asteroids)
marijuana
marine engine
Mariner series
Mariner 2
Mariner 9
maritime climate
Marius, Simon (1573–1624)
Markarian's Chain
Markov chain
marl
Marquardt space sled
MARS
Mars
Mars, ammonia on
Mars, atmosphere
Mars, canals
Mars, caves
Mars, communication with
Mars Curiosity descent
Mars, dust devils
Mars, life
Mars, meteorites from
Mars, methane on
Mars, polar caps
MARS, UNMANNED SPACECRAFT
Mars, vegetation
Mars 1969 A/B
Mars 96
Mars Climate Orbiter
Mars Exploration Rovers
Mars Express
Mars "face"
Mars Global Surveyor
Mars meteorites
Mars Microprobe Mission
Mars Observer
Mars Pathfinder
Mars Phoenix Lander
Mars Phoenix Lander photos
Mars Polar Lander
Mars Reconnaissance Orbiter
Mars Science Laboratory
Mars Scout
Mars Trojan
Mars 2001 Odyssey
Mars-crosser
Marsden, Ernest (1889–1970)
Marshall, George C. (1880–1959)
Marshall Space Flight Center
Marsnik
marsupial
Martian Chronicles, The
martian "fossils" controversy
Martin, Pierre Émile (1824–1915)
Martingale system
Mascall, Eric Lionel (1905–1993)
Mascheroni construction
maser
Maskelyne, Nevil (1732–1811)
mass
mass deficiency
mass discrepancy
mass driver
mass extinction
mass function
mass loss
mass number
mass production
mass spectrometry
mass transfer
mass-energy relationship
masseter
mass-luminosity ratio
mass-luminosity relation
mass-luminosity-radius relation
mass-radius relation
mast cell
MASTIF (Multiple Axis Space Test Inertia Facility)
mastoid bone
Matador
Matagorda Island
match
materialism
mathematical lifespan
mathematical models
MATHEMATICAL TERMINOLOGY
MATHEMATICIANS
MATHEMATICS
mathematics
mathematics and civilization
mathematics as a universal language
Mathilde
mating ritual
Matrioshka brain
matrix
matter
matter-antimatter symmetry
Matthew, William Diller (1871–1930)
Mattingly, Thomas K. II (1936–)
Mauchly, John William (1907–1980)
Maul, Alfred (1864–1941)
Mauna Kea observatories
Maunder, Edward Walter (1851–1928)
maxilla
maxillary artery
maxillary nerve
maxillary sinus
Maxim family
Maxwell, James Clerk (1831–1879)
Maxwell's equations
Mayall Telescope
Mayer, Julius Robert von (1814–1878)
Mayer, Maria Goeppert (1906–1972)
Mayo family
Mayor, Michel (1959–)
maze
McAdam, John Loudon (1756–1836)
McAuliffe, S. Christa Corrigan (1948–1986)
McCandless, Bruce II (1937–2017)
McDermot, Murtagh
McDivitt, James A. (1929–)
McDonald Observatory
McKay, Christopher P.
McKay, David S.
McMath-Pierce Solar Telescope
MDS (Mission Demonstration test Satellite)
mean
mean motion
mean motion resonance
mean place
measles
measure
measuring and weighing puzzles
Méchain, Pierre François André (1744–1804)
mechanical advantage
mechanical equivalent of heat
mechanical programmability
mechanical puzzle
mechanics
mechanization and automation
MECO (main engine cutoff)
Medawar, Peter Brian (1915–1987)
medial
median
median nerve
median sagittal plane
mediastinum
medical diagnostic techniques
MEDICAL TESTS
medicine through the ages
medieval philosophy, related to the possibility of extraterrestrial life
mediocrity, principle
Mediterranean climate
medium Earth orbit (MEO)
medulla
medulla oblongata
medusa
meerschaum
megacatastrophe
MEGACATASTROPHES
megaphone
meiosis
Meissa (Lambda Orionis)
Meissner effect
Meitner, Lise (1878–1968)
Mekbuda (Zeta Geminorum)
melamine
melanin
melanocyte-stimlating hormone (MSH)
melanoma
melanoma treatment
melatonin
melting point
memory
Menaechmus (c. 380–c. 320 BC)
Mendel, Johann Gregor (1822–1884)
mendelevium
Mendeleyev, Dmitri Ivanovich (1834–1907)
Mendelian inheritance
Menger sponge
Ménière's disease
meninges
meningitis
meniscus
meniscus lens
Menkalinan (Beta Aurigae)
Menkent (Theta Centauri)
Menkib (Xi Persei)
Mensa (constellation)
menstrual cycle
menstruation
mensuration
mental illness
mental retardation
menthol
Menzel, Donald Howard (1901–1976)
Merak (Beta Ursae Majoris)
Mercator, Gerardus (1512–1594)
mercury (element)
Mercury (planet)
Mercury Project
Mercury Seven
Mercury Thirteen
Mercury-Atlas
Mercury-Redstone
meridian
Meridiani Planum
meristem
Merope (23 Tauri)
Merope Nebula (NGC 1435)
Mersenne, Marin (1588–1648)
Mersenne number
Mersenne prime
mesa
mescaline
mesentery
mesoderm
mesoglea
meson
mesophiles
mesophyll
mesosiderite
mesosphere
mesothelioma
mesothelium
Mesozoic era
MESSENGER (Mercury Surface, Space Environment, Geochemistry and Ranging)
messenger probe
messenger RNA
Messerschmitt, Wilhelm (1898–1978)
Messerschmitt Me 163
Messier, Charles Joseph (1730–1817)
Messier Catalogue
META, Project
metabolic panel
metabolic syndrome
metabolism
metabolite
metacarpal
metal
metallic bond
metallicity
metalloid
metallurgy
metal-poor star
metal-rich star
metalworking machines
metamorphic rock
metamorphosis
metaphysics
metastasis
metatarsal
metazoan
Metchnikoff, Élie (1845–1916)
meteor
Meteor (Russian satellites)
meteor shower
meteorite
meteorite shower
METEORITES, FAMOUS
meteorites, from Mars
meteoroid
meteorology
meteorological satellite
METEORS AND METEORITES
Meteosat
meter
methanal
methane
methane rocket engine
methanogens
methanol
methionine
methotrexate
Metis
Metonic cycle
MetOp (Meteorological Operational) satellites
metric
metric units
Metrodorus of Chios (fourth century BC)
Meudon Observatory
Meyer, Julius Lothar (1830–1895)
Miaplacidus (Beta Carinae)
mica
Mice, The (NGC 4676 A and B)
micelle
Michell, John (1724–1793)
Michelson, Albert Abraham (1852–1931)
Michelson-Morley experiment
microarray technology
microbe
microbes, temperature ranges of
microbiology
MICROBIOLOGY
microbody
microcline
microfilament
MicroLab
microlensing
Microlensing Observations in Astrophysics (MOA)
Microlensing Planet Search (MPS) Project
Micromegas
micrometeorites
micrometeoroid protection
micrometer
microorganism
microphone
microquasar
MicroSat
microscope
Microscopium (constellation)
microspheres
microtome
microtubule
Microwave Observing Program (MOP)
microwave plasma thruster
microwave radiation
microwave-induced fusion propulsion
MIDAS (Missile Defense Alarm System)
midbrain
middle ear
MIDEX (Medium-scale Explorer)
mid-ocean ridge
Midori (aka ADEOS)
Mie scattering
Mightysat
migmatite
migraine
migration
Milankovich cycles
mildew
mile
MILITARY AIRCRAFT
MILITARY INSTALLATIONS
MILITARY RECONAISSANCE AND SURVEILLANCE
milk
Milky Way
Milky Way Galaxy
Miller, Stanley Lloyd (1930–2007)
Miller-Urey Experiment
Millikan, Robert Andrews (1868–1953)
million
millipede
Millis drives
millisecond pulsar
Mills cross
Milne, Edward Arthur (1896–1950)
Milne, John (1850–1913)
Milstar (Military Strategic and Tactical Relay satellite)
Mimas
mimicry
Mimosa (Beta Crucis)
mind transfer
mind-meld
mineral (geology)
mineral (nutrition)
mineral spring
mineralocorticoid
mineralogy
minimal surface
mining
MiniSat
Minkowski, Hermann (1864–1909)
Minkowski, Rudolph Leo Bernhard (1895–1976)
Minkowski space
Minkowski's Object (Arp 133)
Minor Planet Center
Minotaur (rocket)
Mintaka
Miocene epoch
Mir
Mira
Mira variable
Mirach (Beta Andromedae)
Mirach's Ghost (NGC 404)
mirage
Mirak (Minimum Rakete)
Miranda
Miranda (UK satellite)
Mirfak (Alpha Persei)
mirror
mirror matter
mirror reversal problem
Mirzam (Beta Canis Majoris)
Mishin, Vasily (1917–2001)
missile
missing dollar problem
missing mass
Mission of Gravity
Mission of Opportunity
Mississippi Test Facility
mistral
Mitchell, Edgar Dean (1930–2016)
mite
mitochondria
mitosis
mitotic spindle
mitral regurgitation
mitral stenosis
mitral valve
mitral valve prolapse
Mitscherlich, Eilhardt (1794–1863)
Mittag-Leffler, (Magnus) Gösta (1846–1927)
mixture
Mizar (Zeta Ursae Majoris)
MKS units
MOA
Möbius band
mode
moderator
modular arithmetic
modulation
modulus
Mogul, Project
Mohl, Hugo von (1805–1872)
Mohoroviic discontinuity
Mohr, Karl Friedrich (1807–1879)
Mohs scale
Moiré pattern
Moissan, Ferdinand Frédéric Henri (1852–1907)
molar mass
mold
mole (animal)
mole (unit)
molecular cloud
molecular quantum computing cloud
molecular weight
molecule
molecules, in space
mollusc
Molniya
Molniya launch vehicle
Molniya-type orbit
molting
molybdenite
molybdenum
moment
moment of inertia
momentum
monadnock
monazite
Mond, Ludwig (1839–1909)
Monge, Gaspard (1746–1818)
monism
monkey
monkeys and typewriters
monoamine oxidase
Monoceros (constellation)
monochromatic
monoclonal antibody
monocotyledon
monocyte
Monod, Jacques (1910–1976)
Monogem Ring
monolayer
mononucleosis
monorail
monosaccharides
monosomy
Monotremata
monsoon
Monster group
Monstrous Moonshine conjecture
Monte Carlo method
Montgolfier brothers
month
montmorillonite
Montucla, Jean Etienne (1725–1799)
Monty Hall problem
MOON
Moon
Moon, communication with
Moon base
"Moon Hoax"
"Moon trees"
moons, atmospheres of
moons, life on
moonstone
moor
Moore, Patrick Alfred (1923–2012)
Moore, Stanford (1913–1982)
Mopra Telescope
moraine
mordant
Morelos
Moreton wave
Morgagni, Giovanni Battista 1682–1771)
Morgan, Thomas Hunt (1866–1945)
Morgan, William Wilson (1906–1994)
Morgan-Keenan classification
Morley, Edward Williams (1838–1923)
Morley's miracle
Morokweng crater
morphine
Morrison, Philip (1915–2005)
Morrison's radioglyph scheme
Morse, Samuel Finley Breese (1791–1872)
Morse code
Morton, William Thomas Green (1819–1868)
morula
MOS (Marine Observation Satellite)
mosasaur
Moseley, Henry Gwyn Jeffreys (1887–1915)
mosquito
moss
Mössbauer, Rudolf Ludwig (1929–)
Mössbauer effect
MOST (Microvariability and Oscillations of Stars)
mother-of-pearl
motor
motor nerve
motor neuron
motorcycles, history
Mott, Nevill Francis (1905–1996)
Mottelson, Ben Roy (1926–2022)
Moulton, Forest Ray (1872–1952)
Mount Graham International Observatory (MGIO)
Mount Palomar Observatory
Mount Stromlo and Siding Spring Observatory
Mount Wilson Observatory
mountain life
mountains and mountain-building
mouse model
mouth
moving cluster
moving sofa problem
MPD thruster
MPS Project
MRI (magnetic resonance imaging)
Mrs. Perkins' quilt
MS star
MSX (Midcourse Space Experiment)
MTI (Multispectral Thermal Imager)
M-type asteroid
Mu Arae
mucigel
mucopolysaccharide
mucous membrane
mud volcano
mudstone
Muller, Hermann Joseph (1890–1967)
Müller, Johann (1436–1476)
Müller-Lyer illusion
Mulliken, Robert Sanderson (1896–1986
multigrade
multiple birth
Multiple Mirror Telescope (MMT)
multiple myeloma
multiple proportions, law of
multiple sclerosis
multiplet
multiplication
Multi-Purpose Crew Vehicle
Multi-Purpose Logistics Modules
multiringed basin
multiverse
mumps
Munin
muon
mural circle
Murchison meteorite
Murdock, William (1754–1839)
Muroc Army Air Field
Murray, Bruce C. (1932–2013)
Murray meteorite
Musca (constellation)
muscle
muscle operation and contraction by nerves
muscovite
muscular dystrophy
muscular system
musculoskeletal system disease
MUSES series
Musgrave, (Franklin) Story (1935–)
mushrooms and toadstools
MUSIC
muskeg
Musson
mustard
MUSTARD (Multi-Unit Space Transport and Recovery Device)
mutagen
mutation
MX-324
My Favorite Martian
myalgic encephalomyelitis (ME)
myasthenia gravis
mycobacterial diseases
mycoplasma
mycorrhiza
Mydorge, Claude (1585–1647)
myelin
myocarditis
myoglobin
Myojo
myopia (nearsightedness)
myosin
myriad
myriapod
MYTHS AND LEGENDS