All the planets in the solar system rotate roughly in a plane that intersects the sun.

Stars in the Milky Way rotate around its centre forming a rough planar disk.


Are these planes all parallel? I.e. Do planets of all stars rotate in planes parallel to the plane of the galaxy? Do they rotate in the same direction?

If so, is it

(a) because the whole galaxy evolved from a spinning mass so it naturally turned out that way

(b) because, over time, the 'wheels' that were spinning on other axes were somehow dragged into alignment

(c) Nobody knows

(d) Something else

  • 1
    $\begingroup$ @ProfRob I don't think it's a dupe because this question talks about stars revolving around the galactic plane, while the dupe target talks about detection of exoplanets, which doesn't seem right. $\endgroup$
    – WarpPrime
    Commented Jan 6, 2021 at 14:13
  • $\begingroup$ The plane of the Milky Way is quite separate from the plane of the ecliptic. $\endgroup$
    – antlersoft
    Commented Jan 6, 2021 at 17:03
  • 1
    $\begingroup$ See also astronomy.stackexchange.com/questions/29641/… and astronomy.stackexchange.com/questions/40277/… $\endgroup$
    – ProfRob
    Commented Jan 6, 2021 at 20:18

1 Answer 1


As far as we know exoplanetary systems have orbital planes that are randomly distributed with respect to the Galactic plane. Indeed our own ecliptic plane is quite inclined with respect to the Galactic plane - as one can readily tell from the fact that the planets are not always seen against a background of the Milky Way.

Further details and some references can be found in answers to the related questions Detection of exo-planets and Do the axes of rotation of most stars in the Milky Way align reasonably closely with the axis of galactic rotation?


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