Colliding Supernova Remnants . ... Credit Copyright: Rosa Williams ( UIUC Astronomy Department ), et al. ... This stellar detonation, a supernova , propels vast amounts of starstuff outwards, initially at millions of miles per hour. For another 100,000 years or so the expanding supernova remnant gradually slows as it sweeps up material and ultimately merges with the gas and dust of interstellar space. ... NASA Web Site Statements, Warnings, and Disclaimers . NASA Official: Jay Norris. ...