About 8,000 years ago, Neolithic humans would have witnessed what appeared to be a bright new star blazing in the northern sky. In fact, it was the violent explosion of a star 20 times the mass of our Sun. Now, the expanding remnant of that blast can be seen as the Cygnus Loop, a donut-shaped nebula that is approximately 6 times the apparent diameter of the full Moon. This Hubble image shows a small section of the Veil Nebula. This section of the...
