Between 5,000 and 8,000 years ago, a star many times more massive than our Sun met its end in a fantastic supernova explosion. The supernova remnant–the observable aftermath of that ancient star’s spectacular demise–is known as the Cygnus Loop. Not all of the radiation from the remnant is in the visual spectrum however–meaning our eyes can’t see the entire structure–but the portion that does fall within the visible spectrum is a popular target for professional and amateur astronomers and is commonly referred to as the Veil Nebula.
[Left] – This is a sky survey image of the Veil Nebula, a 110-light-year-wide expanding remnant of a star that exploded about 8,000 years ago in the constellation Cygnus.
[Center] – This is a ground-based telescope image of a 15-light-year-long stretch of the eastern portion of the nebula.
[Right] – This image shows a two-light-year-wide segment of the remnant as photographed by NASA’s Hubble Space Telescope. Hubble resolves tangled rope-like filaments of glowing gases.
What I love about the Cygnus Loop, and most other features of the night sky, is how we can discover more than what just our eyes can see. We often forget, or maybe don’t even realize, that our eyes are only sensitive enough to see a small portion of the entire electromagnetic spectrum. We refer to this narrow band of electromagnetic radiation as visible light.
The part of the Cygnus Loop that’s observable in visible light, which is referred to as the Veil Nebula, looks like this:
Now, if the range of electromagnetic radiation our eyes can sense were expanded just a bit into the ultraviolet part of the spectrum, we’d see the Cygnus Loop like this:
In ultraviolet, otherwise invisible or very faint wisps of gas are much more pronounced and show that there’s much more to this stellar spectacle than meets the eye.