Astronomy Picture of the Day . ... 26.07.1996 . ... Credit Copyright: J. Hester ( ASU ), NASA Explanation: 15,000 years ago a star in the constellation of Cygnus exploded -- the shockwave from this supernova explosion is still expanding into interstellar space! The collision of this fast moving wall of gas with a stationary cloud has heated it causing it to glow in visible as well as high energy radiation , producing the nebula known as the Cygnus Loop (NGC 6960/95). ... July . ... July 1996 . ...