He 2-147: A case in which the expansion parallax method fails

HST multi-epoch images and VLT integral-field, high resolution spectroscopy allowed us a robust determination of the 3-D geometry and orientation of the nebula surrounding He 2-147, and to measure its apparent expansion in the plane of the sky. Applying the expansion parallax method results in a distance which is significantly shorter that the one obtained via the period-luminosity (P-L) relationship for the Mira component. We show how allowing for shock excitation of the nebula, as suggested by the extremely broad nebular line profiles, enables both distance derivations to be reconciled.