Look at the bright star near the left border of the photo: Spica. From a distance you will see a brightening around this star.
This brightening is the Gegenschein, sunlit scattered by interplanetary dust at the antisolar point.
The Gegenschein is really difficult to spot, you need a clear moonless night and the help of a camera, in my photo battling some light pollution it is faintly visible.
Knowing that the antisolar point was near Spica at the time the photo was taken helped a lot.