NGC 6946

Constellation: Cepheus
Distance: 22 million light years

Right Ascension: 20 : 34.8 (hours : minutes)
Declination: +60 : 09 (degrees : minutes)

copyright Robert Gendler


NGC 6946 is one of the nearest giant spiral galaxies beyond the local group. It has a high level of star formation throughout its disk in addition to a strong nuclear starburst region. NGC 6946 has hosted nine supernovae (SN 1917A, SN 1939C, SN 1948B, SN 1968D, SN 1969P, SN 1980K, SN 2002hh, SN 2004et, and SN 2008S) within the last century attesting to its prodigious star forming history. The galaxy is located at low galactic latitude (similar to IC 342) so its light is significantly reddened due to foreground dust in the Milky Way. A peculiar stellar complex exists to the west of the galaxy center, at the end of a sub-branch of one of the main spiral arms. The arc shaped complex was first discovered by Hodge in 1967 and represents one of the brightest and largest young star clusters currently known in the disk of any spiral galaxy. The complex has a diameter of about 2000 light years (similar in size to Gould's Belt, see M45) and is composed of a group of highly luminous star clusters, each similar to the brightest young clusters in the Milky Way.

NGC 6946 has a peculiar multiple arm spiral structure which coalesces into four dominant spiral arms. NGC 6946 has an unusually large halo of neutral gas that extends out of the plane of the disk, rotating at a slower velocity than the disk. Extra-planar gas is a phenomenon peculiar to several other galaxies, including NGC 2403 and NGC 891, two galaxies with high rates of star formation. The phenomenon is likely due to a fountain effect where winds from high mass stars and supernovae blow gas out of the plane of the galaxy forming an extended gaseous halo structure.