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Meson
A meson is a hadron made of one quark and one antiquark bound by the strong interaction, unlike baryons, which contain three quarks; all known mesons are unstable.
Mesoscale convective system
A mesoscale convective system (MCS) is an organized grouping of thunderstorms acting as a single system, spanning thousands of square kilometers and persisting for several hours or more.
Mesoscale eddy
A mesoscale eddy is a rotating body of ocean water, typically 10 to 100 km across, that drifts for weeks to over a year carrying heat and salt.
Mesoscopic physics
Mesoscopic physics, or mesoscience, is the branch of condensed matter physics studying conductors whose size, typically nanometers to micrometers, lets electron phase coherence produce observable quantum interference effects.
Mesosphere
The mesosphere is the third layer of Earth's atmosphere, between the stratosphere and thermosphere at about 50 to 80 kilometers, where most meteors burn up.
Mesotrione
Mesotrione is a selective triketone herbicide, developed by Syngenta and launched in the United States in 2001 as Callisto, used chiefly for weed control in corn.
Mesovortex
A mesovortex is a strong, long-lived, low-level vortex a few kilometers wide that forms in quasi-linear convective systems such as squall lines and bow echoes, and spawns most of their tornadoes.
Mesozoic
The Mesozoic Era, informally the Age of Reptiles, spans 251.9 to 66.0 million years ago and comprises the Triassic, Jurassic, and Cretaceous periods, when dinosaurs dominated the land.
Messier 10
Messier 10 (NGC 6254) is a globular cluster in the constellation Ophiuchus, discovered by Charles Messier in 1764 and located about 15,000 light-years from Earth.
Messier 100
Messier 100 (M100, NGC 4321) is a grand-design spiral galaxy about 56 million light-years away in Coma Berenices and one of the brightest spirals in the Virgo Cluster.
Messier 105
Messier 105 (M105, also known as NGC 3379) is an elliptical galaxy about 32 million light-years away in Leo and home to a supermassive black hole.
Messier 106
Messier 106, also cataloged as NGC 4258, is a Seyfert 2 spiral galaxy in Canes Venatici about 24 million light-years away, known for its anomalous arms driven by its central black hole.
Messier 107
Messier 107 (M107, NGC 6171) is a loose, sparse globular star cluster in the constellation Ophiuchus, about 20,000 light-years from Earth, discovered by Pierre Méchain in 1782.
Messier 109
Messier 109, also cataloged as NGC 3992, is a barred spiral galaxy in Ursa Major about 60 million light-years away, home to about a trillion stars.
Messier 110
Messier 110, also known as NGC 205, is a dwarf elliptical satellite galaxy of the Andromeda Galaxy about 2.7 million light-years from Earth, discovered in 1773.
Messier 12
Messier 12 (NGC 6218) is a globular cluster of roughly 200,000 stars in the constellation Ophiuchus, 23,000 light-years from Earth, discovered by Charles Messier in 1764 and notable for losing low-mass stars to the galaxy's gravity.
Messier 13
Messier 13, also called the Great Globular Cluster in Hercules, is a globular cluster of several hundred thousand ancient stars in the constellation Hercules, about 25,100 light years from Earth.
Messier 14
Messier 14 (M14, NGC 6402) is a globular cluster in Ophiuchus discovered by Charles Messier in 1764, about 29,000 light-years from Earth with more than 150,000 stars.
Messier 15
Messier 15 (M15, NGC 7078), the Great Pegasus Cluster, is a globular cluster about 33,600 light-years away with one of the densest cores in the Milky Way.
Messier 19
Messier 19 (M19, NGC 6273) is a globular cluster in Ophiuchus, discovered by Charles Messier in 1764. It is the most visibly flattened globular cluster in the Milky Way, about 28,500 light-years away.
Messier 2
Messier 2 (M2, NGC 7089) is a globular cluster in Aquarius about 37,000 light-years away, containing over 150,000 stars and spanning more than 150 light-years.
Messier 20
Messier 20, better known as the Trifid Nebula, is a young star-forming region in Sagittarius, about 5,000 light years away, divided into three lobes by dark dust lanes.
Messier 22
Messier 22 (NGC 6656), also called the Sagittarius Cluster, is a bright globular cluster of ancient stars in Sagittarius about 10,000 light-years from Earth, discovered in 1665 and visible to the naked eye.
Messier 27
Messier 27, also known as the Dumbbell Nebula, is a planetary nebula in Vulpecula about 1,200 light-years away, the first discovered by Charles Messier in 1764.
Messier 28
Messier 28 (NGC 6626) is a globular cluster in Sagittarius, about 18,000 light-years from Earth. Discovered by Charles Messier in 1764, it hosts 13 known millisecond pulsars.
Messier 3
Messier 3 (M3, NGC 5272) is a globular cluster of more than 500,000 old stars in Canes Venatici, about 34,000 light-years away, holding more variable stars than any known cluster.
Messier 30
Messier 30 (NGC 7099) is a globular cluster of stars in the constellation Capricornus, discovered by Charles Messier in 1764, about 26,000 light-years away and 13 billion years old.
Messier 32
Messier 32 (M32, NGC 221) is a compact elliptical galaxy 2.5 million light-years away in the constellation Andromeda, a bright satellite of the Andromeda Galaxy with a dense central black hole.
Messier 37
Messier 37 (NGC 2099) is the richest and brightest open star cluster in Auriga, about 4,500 light years away, first recorded before 1654 and cataloged by Charles Messier in 1764.
Messier 4
Messier 4, also cataloged as M4 and NGC 6121, is a globular cluster of over 100,000 stars in Scorpius about 5,500 light-years away, discovered in 1746.