All Topics  
Meridian (astronomy)

 

 
   Email Print
   Bookmark   Link
 

 

Meridian (astronomy)
 
 
  Topics Meridian (astronomy) Topic Home

This article is about the astronomical concept. For other uses of the word, see Meridian.


In the sky, a meridian is an imaginary great circle
Great circle

A great circle of a sphere is a circle that runs along the surface of that sphere so as to cut it into two equal halves. The great circle therefore has both the same circumference and the same center as the sphere....
 on the celestial sphere
Celestial sphere

In astronomy and navigation, the celestial sphere is an imagination rotation sphere of "gigantic radius", concentric spheres and coaxial with the Earth....
. It passes through the north point on the horizon, through the celestial pole
Celestial pole

The north and south celestial poles are the two imaginary points in the sky where the Earth axis of rotation, "infinitely extended", intersects the imaginary rotating sphere of stars called the celestial sphere....
, up to the zenith
Zenith

In broad terms, the zenith is the direction pointing directly above a particular location . Since the concept of being above is itself somewhat vague, scientists define the zenith in more rigorous terms....
, through the south point on the horizon, and through the nadir
Nadir

The nadir is the direction pointing directly below a particular location . Since the concept of being below is itself somewhat vague, scientists define the nadir in more rigorous terms....
, and is perpendicular to the local horizon
Horizon

The horizon is the apparent line that separates earth from sky.More precisely, it is the line that divides all of the directions one can possibly look into two categories: those which intersect the Earth's surface, and those which do not....
.

Because it is fixed to the local horizon, stars will appear to drift past the local meridian as the earth spins.






Discussion
Ask a question about 'Meridian (astronomy)'
Start a new discussion about 'Meridian (astronomy)'
Answer questions from other users
Full Discussion Forum



Encyclopedia


This article is about the astronomical concept. For other uses of the word, see Meridian.


In the sky, a meridian is an imaginary great circle
Great circle

A great circle of a sphere is a circle that runs along the surface of that sphere so as to cut it into two equal halves. The great circle therefore has both the same circumference and the same center as the sphere....
 on the celestial sphere
Celestial sphere

In astronomy and navigation, the celestial sphere is an imagination rotation sphere of "gigantic radius", concentric spheres and coaxial with the Earth....
. It passes through the north point on the horizon, through the celestial pole
Celestial pole

The north and south celestial poles are the two imaginary points in the sky where the Earth axis of rotation, "infinitely extended", intersects the imaginary rotating sphere of stars called the celestial sphere....
, up to the zenith
Zenith

In broad terms, the zenith is the direction pointing directly above a particular location . Since the concept of being above is itself somewhat vague, scientists define the zenith in more rigorous terms....
, through the south point on the horizon, and through the nadir
Nadir

The nadir is the direction pointing directly below a particular location . Since the concept of being below is itself somewhat vague, scientists define the nadir in more rigorous terms....
, and is perpendicular to the local horizon
Horizon

The horizon is the apparent line that separates earth from sky.More precisely, it is the line that divides all of the directions one can possibly look into two categories: those which intersect the Earth's surface, and those which do not....
.

Because it is fixed to the local horizon, stars will appear to drift past the local meridian as the earth spins. You can use an object's right ascension
Right ascension

Right ascension is the astronomical term for one of the two coordinates of a point on the celestial sphere when using the equatorial coordinate system....
 and the local sidereal time
Sidereal time

Sidereal time is a measure of the position of the Earth in its rotation around its axis, or time measured by the apparent diurnal motion of the vernal equinox, which is very close to, but not identical to, the motion of stars....
 to determine when it will cross your local meridian, or culminate
Culmination

In astronomy, the culmination, at a given point, of a planet, star, constellation, etc. is the time within the diurnal motion when it appears on an observer's meridian ....
 (see hour angle
Hour angle

In astronomy, the hour angle is one of the coordinates used in the equatorial coordinate system for describing the position of a point on the celestial sphere....
).

The upper meridian is the half above the horizon, the lower meridian the half below it.