Discovery of a double ring in the core of eta Carinae

We report the discovery of a double ring structure in the waist of the nebu la surrounding eta Carinae. The rings are detected in the mid-IR dust conti nuum at wavelengths of 7.9, 11.9, 12.9 and 20 mum. The dust in the rings ha s a temperature of about 300 K. The orientation of the rings is inclined wi th respect to the axis of the homunculus by either 37 or 58 degrees. The ce ntral star is not in the projected centre of the structure defined by the t wo rings. This geometry is reminiscent of that seen in SN1987A and some pla netary nebulae. We discuss several possible origins for this remarkable geo metry and its orientation.