Cygnus and Vulpecula
Supernova Remnant
RA: 20 51 00
Dec: +31 00 00
(Coordinates of the approximate center)
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Various portions of the Veil Nebula have been discussed here in the past, but this post is about the entire object – the Cygnus Loop. I have a detailed article about each section in the September issue of Sky & Telescope where I also mention how I used an 8-inch f/3.3 Dob to see the entire SNR as a single, coherent object, and how that transformed my conception of this incredible object. This post is about that overall view.
The Cygnus Loop is about 3 degrees in diameter east to west and 3.5 degrees north to south – a huge object to see in one telescope field of view. After I’d completed observing and sketching each segment of the Loop with my 28-inch scope, which was an awesome observing experience all its own, I was curious how much of the Loop I could see with the 8-inch and was blown away that I could see the whole thing! I used an Explore Scientific 100-degree, 25 mm eyepiece with an OIII filter, but without a Paracorr, to achieve a wide enough field.
Last week, two friends were out testing a new pair of 80 mm binoculars equipped with OIII filters, and reported that they too could see the entire Loop by following my drawing. This suggests that many of us have been “missing the forest for the trees” by only looking at the individual segments with our larger telescopes.
As satisfying as that’s been, the full view is in many ways more impressive. Seeing how the supernova shock wave has created this bubble of excited interstellar dust and knowing which parts are expanding away, and toward us, is a rare observation. Granted, you’ll need a truly dark sky for the best view, but you may be surprised by what can be seen through moderately light polluted skies too.
Other than the overall view, I had three big surprises when I sketched the entire Cygnus Loop. First, was stumbling across a major section of the Loop that I didn’t even realize was there – I refer to as the “Fourth Veil” in my S&T article. It parallels the full length of Fleming’s Triangle (which everyone knows as Pickering’s Triangle, but Williamina Fleming was the actual discoverer). NGC’s 6974 and 6979 are the brightest bits on the northern end, but faint wisps flow 3 degrees to the south as well, where they combine with the southern end of Flemings Triangle and the northeastern part of the Southern Blowout Region (SBR).
And that’s the second surprise I encountered. The SBR is an area of lower interstellar dust density that has allowed the SN shockwave to travel through more easily. The eastern arc is actually rather easy to see, while the western arc is probably the most difficult.
My third surprise is the small bit of nebulosity just south of the NGC 6992, 6995 and IC 1340 Eastern Arc. This bit of fluff is called the Southeastern Knot and is an area of interstellar dust the SN shockwave has just started to excite, and is expected to become more prominent over the next few hundred years. For that matter, the SN shockwave probably began exciting all the current main sections of the Loop – which are pre-existing clouds of interstellar dust, not the explosive remains of the SN itself - about 1000 years ago, so it’s a sure bet that every section of the Cygnus Loop will continue evolving along with the Southeastern Knot.
The SN shockwave bubble is expanding in three dimensions, and research shows which direction four of the main sections of the Loop are moving. Fleming’s Triangle is moving away from us, while the “Fourth Veil” is moving toward us. NGC 6960 (the Western Arc) is moving slightly away from us, while the Eastern Arc of NGC 6992, 6995 and IC 1340 is moving slightly toward us. For me, this knowledge makes seeing the entire Loop in one field of view even more satisfying simply because I can now imagine this fascinating object in three dimensions.
For more information and closeup sketches of each section, go to https://tinyurl.com/5tethwpt and scroll all the way to the bottom of the page.
Give it go, and let us know what you see!
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