  Deep Halpha+[N II] CCD images have been obtained in the area of the Pegasus
Constellation. The resulting mosaic covers an extent of ~7.5 degr x ~8.5 degr
and filamentary and diffuse emission is discovered. Several long filaments (up
to ~1 degr) are found within the field, while diffuse emission is present
mainly in the central and northern areas. The filaments show variations in the
intensity along their extent suggesting inhomogeneous interstellar clouds.
Faint soft X-ray emission is also detected in the ROSAT All-Sky Survey. It is
mainly concentrated in the central areas of our field and overlaps the optical
emission. The low ionization images of [S II] of selected areas mainly show
faint diffuse emission, while in the medium ionization images of [O III]
diffuse and faint filamentary structures are present. Spectrophotometric
observations have been performed on the brightest filaments and indicate
emission from photoionized or shock-heated gas. The sulfur line ratios indicate
electron densities below ~600 cm^{-3}, while the absolute Halpha emission lies
in the range of 1.1 - 8.8 x 10^{-17} erg s^{-1} cm^{-2} arcsec^{-2}. The
detected optical line emission could be part of a single or multiple supernova
explosions.
