The Infrared Morphology of eta Carinae

Abstract

We present results of a recent 2-12 μm ground-based infrared (IR) imaging study of Eta Carinae. We discuss the comparative spatial morphology of the bipolar lobes, the ``skirt'' defined by the equatorial ejecta, and the bright features in the core. We derive separate color temperature values of 200, 240, and 420 K for the bipolar lobes, skirt, and core, respectively. The mass of the Homunculus Nebula estimated from thermal dust emission and a standard gas-to-dust ratio is 2.5 M_⊙. Roughly one-fifth of the total mass is contained in the fast-moving equatorial ejecta. These mass estimates, combined with expansion velocities in the lobes and the skirt, lead us to conclude that the 1890 outburst and the Great Eruption of 1843 were almost comparable in terms of total kinetic energy output. We argue that it is unlikely that these eruptions were caused by tidal interactions with a companion star.