De Vaucouleurs Atlas Type: SA(r:)b
Filter: B
Telescope: USNO 1.0-m
North right , East up
Field Dimensions: 11.7 x 10.6 arcminutes
RC3 Type: SA(s)b
RSA Type: Sb(rs)I-II
Surface Brightness Range Displayed: 17.0-26.0 mag per square arcsec
Absolute Blue Magnitude: -21.5
De Vaucouleurs Atlas Description:
NGC 7331 has complex, partly flocculent spiral structure and considerable near-side extinction. That the bulge is significant is evidenced by the ``fattening" of the galaxy's isophotes around the minor axis of the outer disk. In the center, a mini-disk is seen that has an enhanced ridge on one side. In the B-I color index map, this ridge is blue, suggesting the presence of an inner ring. Only half the ring may be seen because of the severe near-side extinction.
NGC 7331 was recently studied by Regan et al. (2004), who noted dramatic changes in the morphology of the galaxy with increasing wavelength . This includes a complete inner ring that is most noticeable at infrared wavelengths. The ring is also detectable in CO. Regan et al. estimate a gas mass of 5x109 M(sun) is contained within the ring.