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Fireworks Galaxy

C12, NGC 6946

A multi-armed spiral galaxy more than 22 million light years from the Milky Way Galaxy, angled to be visible almost perfectly face-on as seen from Earth, with its spiral structure clearly displayed. The Fireworks Galaxy is of the intermediate spiral type, showing signs of a central bar, though this is not so well defined as in a full barred spiral galaxy. From a small central nucleus, its spiral arms wind outwards to a distance of 20,000 light years or more, making the galaxy a little less than half the diameter of the Milky Way.

This is a starburst galaxy, notable for an unusually high rate of stellar formation within its arms. A large number of supernovae have been observed within the galaxy, with at least ten such phenonena having been observed at a remarkable average rate of about one supernova every ten years. This makes the galaxy the most active source of supernovae known, giving rise to its common name of the Fireworks Galaxy.

The Fireworks Galaxy lies almost precisely on the border between Cygnus and Cepheus in the sky. Its precise centre lies within a narrow 'panhandle' of Cygnus that extends northward into Cepheus, placing it formally within Cygnus' border by a matter of few seconds of arc. The entire galaxy has an apparent diameter much greater than this - some eleven arc-minutes - and so its western arms spiral out across the border into Cepheus.

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