An imaginary line in the
sky running from due north to due south through the observer's location and the
zenith.
Detailed Definition:
In astronomy, a meridian is an imaginary line in the
sky that runs from due north to due south, passing through the observer's
location and the zenith. The zenith is the point in the sky that is directly
overhead. The meridian is used to measure the altitude of objects in the sky,
as well as their right ascension and declination. The meridian also marks the
boundary between the eastern and western halves of the sky, with objects east
of the meridian being in the morning sky and those west of the meridian being
in the evening sky.
Etymology:
Latin - medius ‘middle’ + dies ‘day’.
Sample Sentence(s):
"The planet Venus will cross
the meridian at 8:00 pm tonight."
"The altitude of the North
Star above the horizon can be measured relative to the observer's meridian."
"The meridian passage of a
celestial object is the time it crosses the observer's meridian."
