its rotation in the orbital plane changes due to GR. Actually, it would change even without GR. The orbital ellipse is only constant in the ideal two-body prob

its rotation in the orbital plane changes due to GR. Actually, it would change even without GR. The orbital ellipse is only constant in the ideal two-body problem. The fact that planets aren't perfectly spherically symmetric, and the presence of the other planets, also cause the orbits to precess. From the Wikipedia article I linked in my other post: "For Mercury, the perihelion precession rate due to general relativistic effects is 43″ per century. By comparison, the precession due to perturbations from the other planets in the Solar System is 532″ per century, whereas the oblateness of the Sun (quadrupole moment) causes a negligible contribution of 0.025″ per century."