macula
- dark spot.
- magnetosphere
- the region of space in which a planet's magnetic
field dominates that of the solar wind.
- magnetotail
- the portion of a planetary magnetosphere which is
pushed away from the Sun by the solar wind.
- magnitude
- The degree of brightness of a celestial body
designated on a numerical scale, on which the
brightest star has magnitude -1.4 and the
faintest visible star has magnitude 6, with the
scale rule such that a decrease of one unit
represents an increase in apparent brightness by
a factor of 2.512. Also called apparent
magnitude.
- mare
- literally "sea" (a very bad misnomer,
still in use for historical reasons); really a
large circular plain
- Marius, Simon
1573-1624
- (a.k.a. Mayr) German astronomer who gave Jupiter's
"Galilean"
moons their names. He and Galileo
both claimed to have discovered them in 1610 and
likely did so independently. Marius was also the
first to observe the Andromeda Nebula with a
telescope and one of the first to observe
sunspots.
- mensa
- mesa, flat-topped elevation.
- metal
- used by astrophysicists to refer to all elements
except hydrogen and helium, as in: "the
universe is composed of hydrogen, helium and
traces of metals". (Note: this is quite
different from the usual chemistry definition.)
- meteor
- (also "shooting star" or "falling
star") a bright streak of light in the sky
caused by the entry into Earth's atmosphere of a
meteoroid or a small icy particle. Very large,
bright ones are called fireballs
and bolides
- meteorite
- a rock of extra-terrestrial origin found on Earth
- meteoroid
- a small rocky object orbiting the Sun; smaller
than an asteroid
- millibar
- 1/1000 of a bar. Standard
sea-level pressure is about 1013 millibars.
- minor planets
- the official term used for asteroids.
- mons
- mountain (plural: montes)
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