On Wednesday, March 16, 2016 at 4:33:35 AM UTC-6, oriel36 wrote:
It is something that can be noticed from the Fomalhaut system which provides
a default orbital geometry invariably described as 'offset' rather than
elliptical -

As Fomalhaut B has a large difference between its perihelion and aphelion, its
orbit definitely exhibits the nature of orbits set down by Kepler - an ellipse,
with the primary, in this case the star Fomalhaut, at one focus.

It is _low_ eccentricity orbits, like that of the Earth around the Sun, that
are almost indistinguishable from a circle with the Sun's position slightly
offset from the centre (the equant of Ptolemy and all that).

It is unlikely that theorists can work with the solar system's galactic
orbital inputs into annual planetary trajectories

As the motion of the Sun in the galaxy is common to it and the planets which
orbit it, it does not add anything to our understanding of how the planets
orbit the Sun.

The galactic motion of the Solar System is taken into account _when it
matters_, such as in the study of the proper motions of other stars in our sky.

John Savard