  This paper proposes a simple model for the 19th century eruption of Eta
Carinae that consists of two components: (1) a strong wind (MdotM=0.33 Msun/yr;
v=200 km/s), blowing for 30 years, followed by (2) a 1e50 erg explosion in
1844. The ensuing collision between the fast ejecta and the CSM causes an
increase in brightness observed at the end of 1844, followed by a sustained
high-luminosity phase lasting for 10-15 years that matches the historical light
curve. The emergent luminosity is powered by CSM interaction, analogous to the
process in luminous Type IIn supernovae, except with 10 times lower explosion
energy and at slower speeds (causing a longer duration and lower emergent
luminosity). Such an explosive event provides a natural explanation for the
light curve evolution, but also accounts for a number of puzzling attributes of
the Homunculus nebula: (1) rough equipartition of total radiated and kinetic
energy, (2) the double-shell structure of the Homunculus, (3) the apparent
single age and Hubble-like flow resulting from the thin swept-up shell, (4) the
complex mottled appearance of the polar lobes in HST images, arising from
Raleigh-Taylor or Vishniac instabilities, (5) efficient and rapid dust
formation, as seen in Type IIn supernovae, and (6) the fast (5000 km/s)
material outside the Homunculus, arising from the acceleration of the forward
shock upon exiting the dense CSM. In principle, the bipolar shape has already
been explained in earlier studies of interacting winds, except that here the
CSM interaction occurs over only 10 years, producing a thin shell with the
resulting structures then frozen-in to the expanding bipolar nebula. This
self-consistent picture has a number of implications for other eruptive
transients, many of which may also be powered by CSM interaction.
