ON THE FORMATION OF THE HOMUNCULUS-NEBULA AROUND ETA-CARINAE

We have constructed an interacting winds scenario to account far the g eometric and kinematic properties of the Homunculus in eta Carinae as seen in recent Hubble Space Telescope observations. Winds from a giant eruption in 1840-1860 sweep into a small (10(14) cm), dense (similar to 10(14) cm(-3)), 2 M-., near-nuclear toroidal ring. The external med ium is uniform at similar to 2000 particles cm(-3). The ring is all bu t destroyed by the winds in the eruption. Even so, it manages to provi de a good deal of collimation to the mass ejected in the first 20 year s. Subsequent weaker outflows ram into the outburst gas and initiate s urface instabilities and wrinkles. Unlike earlier models, ours is in a ccordance with the observation that no large, extended disklike distri bution is seen around the nebula that could have collimated the bipola r lobes. Models with cooling form essentially ballistic hows (that is, a pair of cones each with a spherical base) whose lateral edges becom e wrinkled by shear instabilities. A new aspect of the radiative model s is the fragmentation of the dense ring, which may help to explain th e thin, radial filamentary structure that is seen in the equatorial re gion of the Homunculus. Adiabatic models become very hot quickly and e xplode through the nascent cones into the confining gas before the den se collar is destroyed. A pair of spherical lobes form. After 150 year s the lobe walls are corrugated by shearing instabilities. These lobes morph into a large, single balloon after about another 300 years.