Edgar Degas once painted over one of his works -- a typical enough practice for any artist. Yet, when the great Impressionist painted Portrait Of A Woman around 1870, he skipped painting a middle layer over the previous painting. Degas just rotated the canvas, painting another portrait of a woman over a previous portrait of a woman. By 1922, the older portrait began to show through on the edges, but the sitter's identity was not known.

Reserachers say in a newly published paper that they have discovered a method to reconstruct the older portrait, even down to the near values of paint colors used, hidden underneath. Using an x-ray beam from a particle accelerator, and moving the painting back and forth just 2 millimeters from the detector, they created a high resolution image of the obscured portrait.

The sitter has been identified as model Emma Dobigny.

Popular Science reports that "this method has been used before, to uncover a hidden portrait in Van Gogh's Patch of Grass in 2008. But while that experiment took weeks to create a lower resolution image, this method took only about a day to gather enough data to recreate the image."