NGC 4631, also known as the Whale Galaxy, is a magnitude +9.3 edge-on barred spiral galaxy in the constellation of Canes Venatici. It has a high surface brightness and therefore is a good target for small scopes. Larger instruments reveal numerous dust clumps and mottling. The central region of NGC 4631 is a starburst region, where intensive star formation is currently taking place.
William Herschel discovered the Whale Galaxy on March 20, 1787. It's located 28 million light-years away and is best seen from northern latitudes during the months of March, April or May.
NGC 4631 is positioned in southwestern Canes Venatici, close to the border with Coma Berenices. This region of the constellation also contains a pair of notable galaxies, NGC 4395 and NGC 4656. At 11th magnitude, both of these galaxies are fainter than the Whale Galaxy. NGC 4656 is located 0.5 degrees southeast of NGC 4631 with both galaxies visible in the same low power field of view. Positioned a further 4 degrees to the northwest is NGC 4395.
In total, NGC 4631 spans 15.2 x 2.8 arc minutes of apparent sky. It appears as a thin slither of light in 100mm (4-inch) refractors. Through larger backyard scopes this galaxy is a stunning sight. It looks large and bright with much texture and mottling visible on the periphery of its disk. It also takes magnification well; so don't be afraid to push up the power to tease out finer details. NGC 4627, a tiny 13th magnitude satellite galaxy, can be seen as a faint oval patch just north of centre of the main galaxy.
NGC 4631 is number 32 in the Caldwell catalogue. It's a member of the NGC 4631 Group, a group of galaxies that also includes NGC 4627 and NGC 4656.
NGC 4631 Data Table
|Object Type||Barred Spiral Galaxy|
|Distance (light-years)||28 Million|
|RA (J2000)||12h 42m 08s|
|DEC (J2000)||+32d 32m 26s|
|Apparent Size (arc mins)||15.2 x 2.8|
|Number of Stars||400 Billion|
|Notable Feature||Member of the NGC 4631 Group|