Dust extinction in the Galactic plane
The image shows our Galaxy, as it would look like to an observer that looks down it.
The axes are Galactic x and Galactic y coordinates in units of parsec (one parsec is about 3.3 light years).
The Sun is at (0, 0).
The color of the image encodes how much light would be extinguished by dust, in e-folds.
I.e. if a pixel has the value of 2, then only a factor of exp(-2)≈13.5% of background light would reach the observer.