NGC 6946: The 'Fireworks Galaxy'

NGC 6946, also known as the Fireworks Galaxy, is a 9th magnitude face-on spiral galaxy positioned on the border between Cepheus and Cygnus. At 22.5 Million light-years it's one of the nearest galaxies outside of the Local Group. In the past 100 years, 9 supernovae  have been observed in NGC 6946, hence the nickname the Fireworks Galaxy.

NGC 6946 was discovered by William Herschel on September 9, 1798. It's best seen from northern locations during the months of October, November and December. From latitudes greater than +30N the galaxy is circumpolar. However, from southern locations it appears low down or never even rises at all.

The galaxy can be found at the cross point between the western part of Cepheus and the northern tip of Cygnus. Star eta Cep (η Cep - mag. +3.4) is positioned 2 degrees northeast of NGC 6946. In the same low power telescope field of view as NGC 6946 is open cluster NGC 6939. This object is easily visible with binoculars (mag. +7.8) and contains about 80 stars in an area spanning a mere 8 arc minutes across, making it one of the richest, most stunning open clusters in the area. At high powers through large scopes, NGC 6939 looks spectacular with dozens of stars filling the eyepiece field of view.

Despite appearing face-on from our perspective, NGC 6946 is quite easy to spot in small scopes. An 80mm (3.1-inch) refractor displays a bright core surrounded by a faint haze. Observer with large scopes will show some mottling in the halo, hinting at the spiral arms. Also noticeable are a number of foreground stars superimposed on the galaxy.

In total, NGC 6946 spans 11.5 x 9.8 arc minutes of apparent sky, which corresponds to a spatial diameter of 75,000 light-years. This is considerably smaller than the Andromeda Galaxy (M31) or the Milky Way but slightly larger than another Local Group member, M33 the Triangulum Galaxy.

NGC 6946 is number 12 in the Caldwell catalogue and number 29 in the Arp Atlas of Peculiar Galaxies.

NGC 6946 Data Table

NGC 6946

Caldwell 12

Object Type Spiral Galaxy

Classification SAB(rs)cd

Constellation Cepheus / Cygnus

Distance (light-years) 22.5 Million

Apparent Mag. 8.9

RA (J2000) 20h 34m 52s

DEC (J2000) 60d 09m 11s

Apparent Size (arc mins) 11.5 x 9.8

Radius (light-years) 37,500

Number of Stars > 100 Billion

Notable Feature Nine Supernovae have been observed in the galaxy in the last 100 years