If all Solar System bodies were point masses, or were rigid bodies having spherically symmetric mass distributions, then an invariable plane defined on orbits alone would be truly invariable and would constitute an inertial frame of reference.
12.
Laplace called the invariable plane the " plane of maximum areas ", where the area is the product of the radius and its differential time change dR / dt, that is, its velocity, multiplied by the mass.
13.
The trajectory of the angular velocity around the angular momentum in the invariable plane is a circle in the case of a symmetric top, but in the general case wiggles inside an annulus, while still being concave towards the angular momentum.
14.
One might reasonably argue that it ought to be measured from the invariable plane ( closer to Jupiter's orbital plane ), but the difference is less than 2?. talk ) 05 : 31, 13 October 2013 ( UTC)
15.
:There are some objects that are inclined well off the invariable plane such as 4 Vesta at 35?and 1566 Icarus at 23? but as you point out, the majority of the mass of the solar sytem is orbiting in one plane.
16.
This plane is sometimes called the " Laplacian " or " Laplace plane " or the " invariable plane of Laplace ", though it should not be confused with the Laplace plane, which is the plane about which resonances are far from the precessing body.
17.
Taken together, these results show that, in an absolute reference frame, the instantaneous angular velocity vector \ boldsymbol \ omega is the point of intersection between a fixed invariable plane and a kinetic-energy ellipsoid that is tangent to it and rolls around on it without slipping.
18.
The labelling of this pole as " south " uses the definition currently endorsed by the International Astronomical Union, namely that the north pole of a planet or satellite is the pole that points above the invariable plane of the Solar System, regardless of the direction the planet is spinning.
19.
To avoid confusion with the " north " and " south " definitions relative to the invariable plane, the poles are called " positive " and " negative . " The positive pole is the pole toward which the thumb points when the fingers of the right hand are curled in its direction of rotation.
20.
:: Also see IAU / IAG Working Group on cartographic coordinates and rotational elements, which explicitly lays out the justification for picking which pole is " north ", while acknowledging that this is a matter of preference . " " The north pole is that pole of rotation that lies on the north side of the invariable plane of the solar system.
