  We compare mid-infrared images of the Antennae galaxies (NGC 4038/39) from
the Infrared Space Observatory, with optical images from the Hubble Space
Telescope. The mid-infrared observations show that the most intense starburst
in this colliding system of galaxies takes place in an off-nucleus reg ion that
is inconspicuous at optical wavelengths. The analyses of the mid-infrar ed
spectra indicate that the most massive stars are being formed in an optically
obscured knot of 50 pc radius, which produces about 15% of the total luminosity
from the Antennae galaxies between 12.5 microns and 18 microns. The
mid-infrared observations reported here demonstrate that the interpretation of
star formation properties in colliding/merging systems based on visible
wavelengths alone can be profoundly biased due to dust obscuration. The
multiwavelength view of this nearby prototype merging system suggests caution
in deriving scenarios of early evolution of high redshift galaxies using only
observations in the narrow rest-frame ultraviolet wavelength range.
