M 2-9 - MOVING DUST IN A FAST BIPOLAR OUTFLOW

Using optical images and spectra of the bipolar nebula M 2-9 we show t hat, in addition to the well-known bright inner nebula, the object has fast, highly collimated outflows reaching a total extent of 115 ''. T hese radially opposed and point-symmetric outer lobes are both redshif ted, leading us to model the radiation from them in terms of light ref lected from moving dust, rather than intrinsic emission. Our polarizat ion images show that the lobes are 60% linearly polarized in a directi on perpendicular to the long axis of M 2-9. This high polarization ind icates optically thin scattering, and lends weight to our dust scatter ing model. Use of this model then allows us to determine the distance to M 2-9 directly from the measured proper motions on images taken ove r a period of more than 16 yrs. The physical and geometrical parameter s of the nebula then follow. M 2-9 is at a distance of 650 pc, is 0.4 pc long, has a luminosity of 550 L., and its outer nebula has a dynami cal age of 1200 yrs, in round numbers. Using the fact that the central object has been constrained to be of low luminosity but of a sufficie ntly high temperature to make the observed OIII, we argue that the cen tral object of M 2-9 has to contain a compact, hot source, and is prob ably a binary.