NGC 7331, also known as
Caldwell 30, is an
unbarred spiral galaxy about 40 million
light-years (12
Mpc) away in the
constellationPegasus. It was discovered by
William Herschel in 1784.=10.5px NGC 7331 is the brightest galaxy in the field of a visual grouping known as the
NGC 7331 Group of galaxies. In fact, the other members of the group, NGC 7335, 7336, 7337 and 7340, lie far in the background at distances of approximately 300-350 million light years.
The galaxy appears similar in size and structure to the
Milky Way, and is sometimes referred to as "the Milky Way's twin". However, discoveries in the 2000s regarding the structure of the Milky Way may call this similarity into doubt, particularly because the latter is now believed to be a barred spiral, compared to the unbarred status of NGC 7331. In spiral galaxies the central bulge typically co-rotates with the disk but the bulge in the galaxy NGC 7331 is rotating in the
opposite direction to the rest of the disk. In both visible light and infrared photos of the NGC 7331, the core of the galaxy appears to be slightly off-center, with one side of the disk appearing to extend further away from the core than the opposite side.
Source: Wikipedia 
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