NGC 6946 – The Fireworks Galaxy
Key Scientific Data
Object type: Intermediate spiral galaxy – SAB(rs)cd
Constellation: Cygnus, near the Cepheus boundary
Other designations: Caldwell 12, UGC 11597, PGC 65001, Fireworks Galaxy
Distance from Earth: approximately 25 million light-years
Diameter: approximately 40,000–50,000 light-years
Apparent size: approximately 11.5′ × 9.8′
Apparent magnitude: approximately 8.9
Inclination: approximately 33°
Right Ascension: 20h 34m 52s
Declination: +60° 09′
Discovered by: William Herschel, 1798
Notable feature: exceptionally high number of observed supernovae
Light-travel time: approximately 25 million years
Description
NGC 6946, the Fireworks Galaxy, is an intermediate spiral galaxy approximately 25 million light-years away. Its nearly face-on orientation reveals a bright central region surrounded by intricate spiral arms, dark dust lanes and young stellar populations.
Although considerably smaller than the Milky Way, it is characterised by vigorous star formation and an unusually high frequency of massive stellar explosions.
Why the Fireworks Galaxy?
NGC 6946 earned its nickname from the ten supernovae observed since 1917, an exceptional number for a single galaxy.
This activity is associated with the formation of massive, short-lived stars that can end their lives in spectacular core-collapse explosions, making NGC 6946 an important laboratory for stellar evolution.
The Mystery of the Disappearing Star
One of its most intriguing events involved N6946-BH1, a massive star estimated at roughly 25 solar masses that briefly brightened before fading dramatically.
Its disappearance without a conventional luminous supernova has been interpreted as a possible failed supernova, in which a massive star collapses directly into a black hole. The interpretation remains under investigation.
Seen Through the Milky Way
Located close to the Galactic plane, NGC 6946 is observed through a dense foreground of Milky Way stars and interstellar dust, which partially absorbs and reddens its light.
The photograph captures this contrast between nearby stars and a distant galaxy, with additional faint background galaxies visible across the field.
What the Colours Reveal
The galaxy's orientation allows its stellar populations to be distinguished: warmer tones dominate the older central region, while blue spiral arms trace younger stars. Pinkish areas indicate ionised hydrogen associated with star formation, and dark lanes reveal interstellar dust.
The image was acquired entirely in broadband LRGB, without additional H-alpha exposures, preserving the galaxy's emission features through the standard colour filters.
A Remarkably Rich Field
The surrounding field contains thousands of foreground Milky Way stars, displaying different colours and brightness levels, alongside several faint background galaxies.
This dense stellar foreground provides a striking perspective on the different distances and structures visible within a single astronomical image.
Curiosities
Discovered by William Herschel in 1798, NGC 6946 is also listed as Caldwell 12.
Despite its apparent magnitude of 8.9, its relatively low surface brightness and foreground extinction make it challenging to observe visually.
Its exceptional supernova record and the possible failed explosion of N6946-BH1 make it particularly valuable for studying the final stages of massive stars.
Looking Back in Time
The light recorded from NGC 6946 began its journey approximately 25 million years ago, during Earth's late Oligocene epoch.
The planet was undergoing significant climatic changes, with expanding grasslands, increasingly diverse mammals and early ancestors of modern elephants, horses and apes.
Humans and their direct evolutionary lineage had not yet appeared. The earliest known hominins would emerge only millions of years later, while modern humans would not evolve until approximately 300,000 years ago.
Throughout this immense span of evolution, the photons captured in this image were travelling towards Earth.
Image Data
Total integration time: 17h 59m 3s
Integration by filter:
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Luminance/Clear: 5h 20m (64 × 300")
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Red: 4h 33m 48s
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Green: 3h 59m 45s
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Blue: 4h 5m 30s
Equipment:
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Telescope: Artesky ARTEC 250 Pro
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Camera: Player One Poseidon-M Pro
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Mount: 10Micron GM2000 HPS II
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Filters: Antlia V-Pro LRGB 2"
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Accessories: Pegasus Astro Prodigy Microfocuser, Player One Phoenix Wheel 7×2", WandererAstro WandererCover V4-EC
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Software: Adobe Photoshop, Pleiades Astrophoto PixInsight, Stefan Berg Nighttime Imaging 'N' Astronomy (N.I.N.A. / NINA)
For further information and the full-resolution image, visit AstroBin: