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We investigate, using the modeling code SHAPE, the three-dimensionalstructure of the bipolar Homunculus nebula surrounding Eta Carinae, as mappedby new ESO VLT/X-Shooter observations of the H2 $\lambda=2.12125$ micronemission line. Our results reveal for the first time important deviations fromthe axisymmetric bipolar morphology: 1) circumpolar trenches in each lobepositioned point-symmetrically from the center and 2) off-planar protrusions inthe equatorial region from each lobe at longitudinal (~55 degrees) andlatitudinal (10-20 degrees) distances from the projected apastron direction ofthe binary orbit. The angular distance between the protrusions (~110 degrees)is similar to the angular extent of each polar trench (~130 degrees) and nearlyequal to the opening angle of the wind-wind collision cavity (~110 degrees). Asin previous studies, we confirm a hole near the centre of each polar lobe andno detectable near-IR H2 emission from the thin optical skirt seen prominentlyin visible imagery. We conclude that the interaction between the outflowsand/or radiation from the central binary stars and their orientation in spacehas had, and possibly still has, a strong influence on the Homunculus. Thisimplies that prevailing theoretical models of the Homunculus are incomplete asmost assume a single star origin that produces an axisymmetric nebula. Wediscuss how the newly found features might be related to the Homunculusejection, the central binary and the interacting stellar winds. We also includea 3D printable version of our Homunculus model.

The three-dimensional structure of the Eta Carinae Homunculus