  In order to model the Fermi bubbles we apply the theory of the superbubble
(SB). A thermal model and a self-gravitating model are reviewed. We introduce a
third model based on the momentum conservation of a thin layer which propagates
in a medium with an inverse square dependence for the density. A comparison
have been made between the sections of the three models and the section of an
observed map of the Fermi bubbles. An analytical law for the SB expansion as
function of the time and polar angle is deduced. We derive a new analytical
result for the image formation of the Fermi bubbles in an elliptical framework.
