Discovery of a double ring in the core of η Carinae^*

¹ Astronomical Institute "Anton Pannekoek" , University of Amsterdam, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands
² Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, Celestijnenlaan 200B, 3001 Heverlee, Belgium
³ Sterrewacht Leiden, Postbus 9513, 2300 RA Leiden, The Netherlands
⁴ European Southern Observatory, Karl-Schwarzschild Strasse 2, 85748 Garching, Germany
⁵ SIRTF Science Center, Caltech, Mail Code 314-6, 1200 East California Boulevard, Pasadena, CA 91125, USA
⁶ University College London, Department of Physics and Astronomy, Gower Street, WC1E 6BT London, UK
⁷ Institut d'Astrophysique Spatiale, Bât. 121, Université de Paris Sud, 91405 Orsay Cedex, France

Corresponding author: S. Hony, hony@astro.uva.nl

Received: 14 May 2001
Accepted: 21 August 2001

Abstract

We report the discovery of a double ring structure in the waist of the nebula surrounding η Carinae. The rings are detected in the mid-IR dust continuum at wavelengths of 7.9, 11.9, 12.9 and 20 μm. The dust in the rings has a temperature of about 300 K. The orientation of the rings is inclined with respect to the axis of the homunculus by either 37 or 58 degrees. The central star is not in the projected centre of the structure defined by the two rings. This geometry is reminiscent of that seen in SN1987A and some planetary nebulae. We discuss several possible origins for this remarkable geometry and its orientation.