Line-of-sight stellar inclinations (i *, orange) compared with the orbital inclinations of substellar companions (i o , blue). In these “boomerang diagrams,” stellar inclinations are mirrored about the x–y sky plane (i = 90°) because angular momentum vectors may point toward or away from the observer looking down along the z-axis (as depicted in the bottom-right panel of Figure 10). If i o agrees with i * (e.g., HD 49197), this implies that the host and companion are consistent with spin–orbit alignment; however, the true spin–orbit angle may nevertheless be nonzero in these cases. If i o and i * disagree (e.g., Gl 504), the system is misaligned by at least the difference in the inclination angles. See Sections 2 and 4.7 for details.