Talk:Invariable plane

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[edit] Orbital axes ?

I don't understand your phrase "the rotational axes are not parallel to the orbital axes" (3rd para.). It seems to make no sense. Do you perhaps mean "orbital planes" ? Kiwi137 12:12, 23 April 2007 (UTC)

The rotational axis of a planet is its spin axis, around which it rotates. Earth's rotational period is 24 hours. The orbital axis of a planet is a line perpendicular to its orbital plane, passing through the center of mass of the solar system, around which it revolves. Earth's orbital period is 365¼ days. Earth's rotational axis is tilted 23.5° to its orbital axis, which causes the seasons. Thus Earth's rotational axis is not parallel to its orbital axis. — Joe Kress 20:14, 23 April 2007 (UTC)

Thanks Joe, that makes it much clearer. I can follow the reasoning in the article now.--Kiwi137 21:45, 24 April 2007 (UTC)

[edit] Couple of questions

1) What is the inclination of the invariable plane with respect to a) the galactic plane; and b) the ecliptic? 2) The article says that the barycenter moves over time. Does the plane's inclination change as well? (The article only says that the orbital planes for the planets fluctuate.) SharkD (talk) 02:11, 15 February 2008 (UTC)

The plane of Earth's orbit is the plane of the ecliptic so the inclination of the invariable plane to it is already in the article. I've corrected the article to state that the Sun moves, not the barycenter. The invariable plane does not move so its inclination relative to inertial space does not change. The orbital planes of all the planets move relative to the invariable plane and to inertial space.— Joe Kress (talk) 01:44, 14 November 2008 (UTC)

[edit] Question

Is the sun's angular momentum included in these calculations? --Stepheng3 (talk) 17:17, 1 April 2009 (UTC)

Yes—both the Sun's axial angular momentum and its orbital angular momemtum around the barycenter of the solar system, which is usually outside the Sun, is included within the 2% non-jovian residual as the article states: "The orbital angular momenta of the Sun and all non-jovian planets, moons, and minor solar system bodies, as well as the axial rotation momenta of all bodies, including the Sun, total only about 2%." — Joe Kress (talk) 19:26, 1 April 2009 (UTC)