NGC 6946 is a marvellously handsome-looking galaxy, with its engaging ‘pinwheel’ spiral construction set in a star-sparkling area for these imagers in search of the prettiest of images. But, it’s additionally of supreme curiosity to science-seeking amateurs {and professional} astronomers alike, with its extraordinary propensity to yield exploding stars. This has led to its very apt nickname of ‘The Fireworks Galaxy’!
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NGC 6946, additionally catalogued as Caldwell 12, is an intermediate spiral galaxy (it has the classification SAB(rs)cd, below the Hubble/de Vaucouleurs system) straddling the boundary between the constellations of Cygnus and Cepheus. On August nights it’s splendidly positioned for commentary throughout the UK, mendacity virtually on the zenith at midnight BST mid-month, from London.
It’s not a simple galaxy to search out as its rapid locale shouldn’t be brimming with shiny stars. Strive ranging from magnitude +2.5 Alderamin (alpha [α] Cephei) after which find eta (η, magnitude +3.4) Cephei 4 levels to the south-west; NGC 6946 lies an extra two levels in the identical route. NGC 6946 is likely one of the closest ‘large’ spiral galaxies past our Native Group (it lies about 22 million mild years away), so it has a fairly shiny catalogued magnitude of +8.9. Nonetheless, being a spiral galaxy that’s oriented face-on to our perspective, it’s by a notoriously low floor brightness throughout its substantial 11 × 10 arcminute kind, which makes it a troublesome goal for smaller-aperture telescopes.
Deep newbie photographs routinely present glittering H-II areas and younger star clusters, testomony to a excessive stage of ongoing star formation. This can be one motive why NGC 6946 is awfully prolific at producing supernovae; ten (designated 1917A, 1939C, 1948B, 1968D, 1969P, 1980K, 2002hh, 2004et, 2008S and 2017eaw) have been noticed over the previous 100 years or so!
NGC 6946 ought to be captured visually by a 150mm (six-inch) telescope on a advantageous evening at a dark-sky location, however don’t anticipate to see greater than a uniformly-lit diffuse and faint halo. A 400mm (16-inch) aperture could reveal a number of the H-II areas that liberally dot the galaxy’s a number of spiral arms.
When you’ve had your fill of the galaxy, there’s a pleasant bonus awaiting because the welcoming open cluster NGC 6939 lies simply over half a level away to the north-west. It’s a a lot simpler visible proposition and a advantageous sight by any telescope. Shining with an built-in magnitude of +7.8 because of the mixed mild of maybe 120-140 stars crammed into an obvious diameter of 8’, NGC 6939 is seen in finderscopes on a superb evening. NGC 6946 and NGC 6939 pair make an amazing goal for wide-field imagers.
