"The surface of the Earth is the shore of the cosmic ocean... Recently, we've managed to wade a little way out, and the water seems inviting." - Carl Sagan
Filaments in the Cygnus Loop
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 onboard the Hubble Space Telescope, the picture is a closeup of a supernova remnant known as the Cygnus Loop. The nearly edge-on view shows a small portion of the immense shock front moving toward the top of the frame at about 170 kilometers per second while glowing in light emitted by atoms of excited Hydrogen gas. Situated at over 1,440 light-years away, the Cygnus Loop is thought to have been expanding for 5 - 10 thousand years.
Image credit: William P. Blair and Ravi Sankrit (Johns Hopkins University), NASA