Accretion Disk Simulation . ... The graceful spiral structure seen in this computer visualization does not portray winding spiral arms in a distant galaxy of stars . Instead, the graphic shows spiral shock waves in a three dimensional simulation of an accretion disk -- material swirling onto a compact central object that could represent a white dwarf star , neutron star , or black hole . ... NASA Web Site Statements, Warnings, and Disclaimers . NASA Official: Jay Norris. ...