Well, i added "The Dark Star" graphics (distortion halo, blackened texture & UV_slappy boxie) into the corresponding folder in a Mod (..\GFX\Stars) - then, proceeded to edit the actual default StarTypes.xml file by adding the proper values and definition tags (right after "Sol") - gave it the #8 slot for type - lowered the RGB colors to 0.1 - internal named it "Dark" - linked the Texture & Halo lines to the pngs - copied the xml into (..\Data\.in_root.) AND, the result looks like this:

Be patient, since these are always distributed at random (for sandbox mode)... it may take awhile before your get to see yours in action; the bigger maps do actually raise the odds of extra stars being used.