  We report the discovery of a double ring of emission-line regions around the
nucleus of the Blue Compact Dwarf (BCD) galaxy Mrk409 as seen by deep,
ground-based Halpha images. Echelle spectroscopy obtained at Magellan-I with
MIKE shows the presence of ionized gas flowing out of the galaxy from a very
massive (>7E6 Msun) nuclear starburst with projected expansion velocities of
\~50 km/s. Different scenarios for the formation of these rings are discussed.
While the innermost, nuclear ring is most probably formed by the interaction of
a starburst-driven shock with the surrounding interstellar medium, the origin
of the outer ring is less clear.
