Astronomy Picture of the Day for 9/1/12, this is spiral galaxy NGC 6946 face on.

The yellow colours are old stars, younger star clusters are blue and the reddish ones are stars that are forming in the spiral arms. The galaxy is 40,000 light years across. That’s an astonishing 40,000,000,000,000,000 kilometres (give or take.)

NGC 6946 is known as the Fireworks Galaxy and it does have the aspect of a catherine wheel.