Definition of the IAU for the ecliptic plane

In summary, the International Astronomical Union (IAU) defines the ecliptic plane as being explicitly determined by the mean orbital angular momentum vector of the Earth-Moon barycenter in the Barycentric Celestial Reference System (BCRS). This plane is defined by a normal vector and a point on the plane, with the normal vector coming from the mean orbital angular momentum vector. The mean value is computed over time or location. The center of the sun is not used as a point defining the plane, instead it is either the center of the Barycentric Celestial Reference System or the center of the path of the center of the sun. The document "ON THE DEFINITION AND USE OF THE ECLIPTIC
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How is the definition of the IAU for the ecliptic plane?

In particular I am interested how the perturbations are treated. Neither the earth nor the common gravity center of earth and moon move on an exact plane around the sun.
How is the definition of the IAU for the ecliptic plane?

In particular I am interested how the perturbations are treated. Neither the Earth nor the common gravity center of Earth and moon move on an exact plane around the sun.

I found the IAU document “Adoption of the P03 Precession Theory and Definition of the Ecliptic” at https://www.iau.org/static/resolutions/IAU2006_Resol1.pdf.

It goes, “... that the ecliptic pole should be explicitly defined by the mean orbital angular momentum vector of the Earth-Moon barycenter in the Barycentric Celestial Reference System (BCRS), ...”

A (ecliptic) plane could be defined by a normal vector of the plane and one point which lies on the plane.

The normal vector probably comes from the “mean orbital angular momentum vector”. Does the “mean orbital angular momentum” refer to one revolution of the earth-moon system? How is the mean value computed, over time or location or something else?

What point is taken for defining the plane finally? The center of the sun will also wobble a little bit during one year. Is the center of the path of the center of the sun taken as point defining the plane? Or ts it the center of the Barycentric Celestial Reference System taken?

Thanks!
 
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The document “ON THE DEFINITION AND USE OF THE ECLIPTIC IN MODERN ASTRONOMY” explains why the classical ecliptic plane is no longer needed as reference system in modern astronomy. State of the art is the International Celestial Reference System (ICRS).

The classical ecliptic plane is not more explicitly explained as in the document I mentioned originally. I cannot derive an answer to my question from that document.

Thanks, anyway.
 
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FAQ: Definition of the IAU for the ecliptic plane

1. What is the definition of the IAU for the ecliptic plane?

The International Astronomical Union (IAU) defines the ecliptic plane as the imaginary plane that contains the Earth's orbit around the Sun. It is used as a reference for measuring the positions of celestial objects in the sky.

2. How is the ecliptic plane related to the Earth's orbit around the Sun?

The ecliptic plane is the plane that contains the Earth's orbit around the Sun. This means that the Earth's path around the Sun lies on this plane, and all other planets in our solar system also orbit the Sun on or near this plane.

3. Why is the ecliptic plane important in astronomy?

The ecliptic plane is important in astronomy because it serves as a reference for measuring the positions of celestial objects in the sky. It also helps astronomers understand the motion and alignment of planets, stars, and other objects in our solar system.

4. How is the ecliptic plane determined?

The ecliptic plane is determined by the Earth's tilt on its axis, which is approximately 23.5 degrees. This tilt causes the Earth's equator to be inclined at the same angle to the plane of its orbit around the Sun, creating the ecliptic plane.

5. Does the ecliptic plane have any other significance?

Yes, the ecliptic plane also has cultural and historical significance. It is the basis for the zodiac signs and is used in many ancient calendars, such as the Mayan and Egyptian calendars. It also plays a role in various religious and spiritual beliefs.

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