How was the Cygnus Loop formed?
This nebula is the product of a supernova explosion; in this section, the blast wave has encountered an area of dense interstellar gas, creating turbulence in the wave and causing it to glow. The picture is a composite of three images taken by the Hubble Space Telescope.
The Cygnus Loop was formed by the explosion of a star approximately 10,000 years ago, which ejected its mass into space as a supernova remnant.12
As this remnant expanded, it created a shock wave that propagated into the surrounding interstellar medium. The characteristic "patchy" or filamentary appearance of the loop is attributed to this shock wave encountering small clouds of denser material within the interstellar medium.2
Today, the Cygnus Loop continues to expand at a rate of approximately 100 km (60 miles) per second and remains a notable source of radio waves and X-rays.12