NGC 6946 - The Fireworks Galaxy

The annotated version showing all kinds of interesting objects, mostly other galaxies!

When William Herschel pointed his 40-foot Telescope to the skies on the 9th of September 1798 he noticed a "Nebula" and logged it. But only after the discovery of the hidden properties of the emitted light we could use that as a tool to get a ballpark estimation of the distance and exact composition. Only then it became clear we were looking at a galaxy much like our own, but roughly one third the size.

So what do we see in this picture?

First and foremost a lot of stars! All of these stars are within our own galaxy which we call the milky way. And to elaborate on that; nearly all stars will actually be relatively close to Earth as we can't even properly see the more distant stars in our own galaxy. The clump of stars we see on the right side are an open cluster called NGC 6939.

But the most prominent feature in this photograph is no doubt the galaxy C12. However do not let looks deceive you; it might appear the galaxy and the stars are all one happy family but nothing is "further" from the truth; C12 is very, very far away compared to any of the stars in this picture!

Why fireworks?

There's something else that stands out as well, which is where this galaxy gets it's name from. Supernovae are epic cosmic explosions of massive stars that can outshine vast part of their galaxy, and if you're able to spot them you have witnessed a truly rare phenomenon indeed! Not so with NGC 6946; within the span of 1 century (1917 - 2017) ten(!) supernovae have been confirmed to have occurred in this galaxy. In cosmic terms that is like a rapid machine gun! So the nice colours are *not* the reason why it got it's name!

Later on this galaxy was added to the famous Caldwell catalogue (https://en.wikipedia.org/wiki/Caldwell_catalogue) as C12, and it remains a very popular target.

Are we there yet?

I mentioned the galaxy is much farther away than any of the stars in this picture. Just to get a grasp of the difference in distances; suppose you were able to walk to the furthest star in this picture within the hour.
You decide to walk to C12, pick up your backpack and walk towards it. But being human as you are after eight hours of straight walking you see you're not there yet and set up camp to walk another day for eight straight hours. It would then take you 19 days (no weekends off!) to reach C12!

But wait!

If you're there anyways, why not visit one of the neighbours? See that smudge at 4 o'clock, number 14? That's UGC 11583, another galaxy at just another 3,5 days walk away, so part of the local community over there! Have a good time over there, take a good look at all the other galaxies in view (13 in total , fireworks galaxy and the one you're in excluded) sing kumbayah under the fireworks sky of C12 and when you're done you can hike back for 22,5 days. And just one hour before you smell your own bed you encounter the first stars you could recognize from your window.

Now that was an epic hike, the universe is awesome!


About the Fireworks Galaxy

  • Right ascension:

  • Declination: 20h 34m 52.3s

  • Distance: +60° 09′ 14″

  • Size: 26.77 kpc (87,300 ly)

  • Apparent magnitude (V): +9.6

  • Apparent dimensions (V): 16.0 x 11.2 arcmin

  • Constellation: Cepheus & Cygnus

  • Designations: NGC 6946, UGC 11597, PGC 65001, Arp 29,[1] Caldwell 12


About the photo

74 images of 5 minutes each

  • Acquired over 6 nights between May and June 2024
  • Total integration time: 6H10Min
  • Imaging location: Zaltbommel (NL)
  • Taken under a Bortle 6.4 sky

Equipment used

  • Imaging telescope:
    TS Optics Apochromatic 115/800 mm PHOTOLINE with a 0.79x Focal reducer resulting in F/5.5@623mm Focal lenght
  • Imaging camera:
    ZWO ASI183MC Pro (CMOS)
  • Mount:
    Equatorial iOptron GEM45
  • Guiding telescope:
    William Optics Refractor 200 Guidescope AC 50/200
  • Guiding camera:
    ZWO Optical ASI290mm Mini (CMOS)
  • Filters:
    Optolong L-Ultimate 2.00" 3nm
  • Processed in PixInsight