# Is there a preference for orbital planes of planetary systems to be aligned with the galactic disk?

I'm not sure for how many planetary systems we have a fairly good idea of the inclination and "argument of periapsis" of the orbital plane. I'm assuming there are a number of them that we can estimate due to co-planar assumptions in a multi-planet system or some other means.

I am asking if there are enough "known" orbital planes that we can have some statistical idea whether or not the orbital planes are somewhat aligned with the galactic plane or whether local forces would dominate galactic orbit angular momentum. (I'm thinking the latter is true.)

We would have to keep in mind of course that a system "directly above" us and parallel to the galactic plane would be "face on".

• I think that this problem would be very difficult to answer because almost all of our detection methods rely on us being able to see the system edge-on. Since our system is aligned with the galactic disk, most of the systems we can find are also aligned with the disk. I suppose you could make an assumption that every star has a planetary system, then take a volume of space and count how many systems we know of. The remaining stars would have systems that aren't as aligned with the galactic disk. – Phiteros Mar 26 '17 at 23:54
• I just reviewed orbital elements and found out that the "argument of periapsis" can be known as the "argument of periastron" and a third element is known as the "longitude of the ascending node". I think I've got it now. – Jack R. Woods Mar 27 '17 at 1:39
• Somewhat confused as to how that answers your question, but okay. – Phiteros Mar 27 '17 at 1:40
• @Phiteros I don't follow your argument. A transiting/doppler-detected planet can be rotated by any angle around our line of sight and yield the same observational result. The orbital plane is undefined. – Rob Jeffries Mar 27 '17 at 6:44
• I don't see how the argument of periapsis applies to the rest of this question. – zephyr Mar 27 '17 at 12:46