> Assuming an astronomical object is a member of a two-body system and
> has a spin axis and an orbital plane, can the object's spin axis
> precess around an axis /other/ than the normal to its orbital plane?

> Doesn't seem likely, not with only two bodies.

> Okay, add a few more bodies.

> Take the Moon, for example.  Its spin axis precesses about the normal
> to its orbital plane.  

> Why couldn't its spin axis also precess around the normal to the
> ecliptic?

> Or does it, but to a very much smaller degree?

> Is that what nutation is?  A smaller and faster precession around some
> other axis superposed on a somewhat larger and slower "main"
> precession?