  We have studied the newly-discovered microquasar in NGC 7793 in radio,
optical and X-ray bands. This system comprises a large (250 x 120 pc)
line-emitting optical nebula, detected in H-alpha and HeII 4686. The optical
nebula coincides with a synchrotron-emitting radio cocoon, with a radio
luminosity about 4 times that of Cas A. The central black hole appears as a
hard X-ray source with a point-like, blue optical counterpart. Two prominent
radio lobes are located at the extremities of the cocoon. Just ahead of the
radio lobes, we found two X-ray hot spots, which we interpret as a signature of
the bow shock into the interstellar medium. The X-ray hot spots, radio lobes,
X-ray core and major axis of the cocoon are well aligned, proving that the
system is powered by a jet. From the X-ray data, we estimate a jet power ~ a
few times 10^{40} erg/s, active over a timescale ~10^{5} yrs. This
extraordinary system is a long-sought analog of the Galactic microquasar SS
433.
