Definition of the IAU for the ecliptic plane

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Summary:

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.

Main Question or Discussion Point

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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Tom.G
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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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