Filaments in the Cygnus Loop . ... Credit Copyright: William P. Blair and Ravi Sankrit ( Johns Hopkins University ), NASA Explanation: Subtle and delicate in appearance, these are filaments of shocked interstellar gas -- part of the expanding blast wave from a violent stellar explosion. Recorded in November 1997 with the Wide Field and Planetary Camera 2 on board the Hubble Space Telescope, the picture is a closeup of a supernova remnant known as the Cygnus Loop . ... NASA Official: Jay Norris. ...