MAA Glossary

M


Magnitude, stellar:
A scale for expressing the brightness of a celestial object. Each unit change of a magnitude implies a change of 2.512 times in brightness. Thus 5 magnitudes correspond to a brightness ratio of 100 times, 10 magnitudes to 10,000 times, and so on. A star barely visible to the naked eye on a clear, moonless night is approximately of 6th magnitude. The brightest stars are of 1st, zero, or even negative magnitude.

Meridian, celestial:
The great circle passing through the north and the south points of the horizon and the observer's zenith.

Meteor:
A body of rock or metal that on entering the earth's atmosphere is heated to incandescence by friction. More about meteors can be found in the glossary for comets and meteors by Gary Kronk.

Meteor Shower:
A display of meteors related to one another by motion in parallel path. A list of meteor showers can be found in the meteor shower calendar sorted for each month of the year (by G. Kronk). A very brief overview is available, too.

Meteorit:
Surviving portion of a meteor after traversing the earth's atmosphere and striking the earth.