NGC 7331 (Pegasus)
Fig. 1 - The bulge of the galaxy rotating in the opposite sense to the disk: The spiral galaxy NGC 7331 in Pegasus, photographed with an 8-inch f/5 Newtonian reflector on a ZWO AM5 mount.
| Object name: | Constellation: | Coordinates: | Apparent size: | Visual brightness: |
|---|---|---|---|---|
| NGC 7331 | Pegasus | 22h37m / +34°25' | 10.5' x 3.7' | 9.5 mag |
The unbarred spiral galaxy NGC 7331 (Caldwell 30) in the constellation Pegasus. NGC 7331 appears similar in size and structure to the Milky Way, and is sometimes referred to as 'the Milky Way's twin'. However, the Milky-Way is 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.
NGC 7331 measures 140,000 light-years in diameter and is 44 million light-years from Earth. It was discovered by German-born British astronomer and composer William Herschel in 1784 (source: Wikipedia).
Exposure time: 6h 30min (130x3min) at gain 100 and -10°C, taken on September 27 / 28, 2025 and on September 29 / 30, 2025. Processing with Astro Pixel Processor (APP) and Photoshop. Darks, flats, and bias were used.
Equipment: Cooled ASI 2600MC Pro camera, TeleVue Paracorr Type II coma corrector, 8" f/5 "ONTC" Newtonian telescope riding on a ZWO AM5 Strain Wave Mount, ZWO OAG-L off axis system, ASI 174MM Mini guide camera, ASIAIR Plus.
NGC 7331 was also captured with a 16-inch dobsonian on an equatorial platform. The image can be seen here.
Fig. 2 - Larger image version with labels (click on image).
Fig. 3 - Search chart for NGC 7331. Copyright 2025 'The Mag-7 Star Atlas Project', www.siaris.net.