Yes. A common fix is to separate the low-frequency background from the fine detail, then remove only the background.

In GIMP, one simple method is:

1. Duplicate the image layer.
2. Set the top layer mode to Grain Extract.
3. Apply a strong Gaussian blur to that top layer—enough to smooth out the vignette, but not so much that bright objects create halos.
4. Use Curves or Levels afterward to restore the black point and contrast, since the result will look gray/flat.

A more advanced option is wavelet decomposition. This splits the image into layers by detail scale. The lowest-frequency “Residual” layer contains the broad background/vignetting. Darkening or filling that residual layer can remove the gradient while leaving stars and galaxies in the higher-detail layers.

For future shots, reducing vignetting at capture can help: stop the lens down by 1–2 stops and lengthen exposure if needed. Wide-open lenses often vignette much more than when slightly stopped down.