Deep H \alpha + [ N ii ] CCD images have been obtained in the area of the Pegasus Constellation .
The resulting mosaic covers an extent of \sim 7°.5 \times 8°.5 and filamentary and diffuse emission is discovered .
Several long filaments ( up to \sim 1° ) 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 \sim 600 cm ^ { -3 } , while the absolute H \alpha emission lies in the range of 1.1 – 8.8 \times 10 ^ { -17 } erg s ^ { -1 } cm ^ { -2 } arcsec ^ { -2 } .
The detected optical line emission could be part of a single or multiple supernova explosions .