NGC 185, also known as Caldwell 18, is a dwarf spheroidal galaxy located in the southern part of Cassiopeia. It's about 2 Million light-years distant and like neighbouring dwarf galaxy NGC 147 is a satellite of the Andromeda galaxy (M31) and therefore a member of the Local Group. NGC 185 shines at mag. +9.1.
Dwarf spheroidal galaxies are similar to dwarf elliptical galaxies except they are spheroidal in shape, generally of a lower luminosity and recognised only as Local Group satellite galaxies. They are also believed to contain large amounts of dark matter.
NGC 185 was discovered by William Herschel on November 30, 1787. It was first photographed between 1898 and 1900 by James Edward Keeler using the 36-inch (910 mm) "Crossley Reflector" telescope at the Lick Observatory in California, USA.
For a dwarf galaxy, NGC 185 is interesting as it contains an active galactic nucleus (AGN). It's sometimes classified as a type 2 Seyfert galaxy although this is debatable, but if correct, it would mean that it's the closest Seyfert galaxy to Earth and the only known galaxy of this type in the Local Group. Most galactic star formation in this galaxy took place an extremely long time ago.
A good starting point for locating NGC 185 is bright star, Schedar (α Cas - mag. +2.2), in the "W" asterism of Cassiopeia. An imaginary line extending 8 degrees southwards from this star leads to the galaxy. Omicron Cassiopeiae (ο Cas - mag. +4.5) is a degree east of NGC 185 with NGC 147 a degree west of NGC 185.
NGC 185 is within the range of small and medium size amateur scopes. It has an apparent size of 11.4 x 10.0 arc minutes, but visually it appears much smaller. Through an 80mm (3.1-inch) refractor, this galaxy is fairly simple to spot and considerably easier than NGC 147. It appears as a small faint oval patch of hazy light with no obvious centre that covers about 2 to 3 arc minutes. Through larger reflectors, of the order of 200mm (8-inch) or greater, the galaxy is slightly brighter and more defined, especially towards the centre. On good nights, it may be even possible to notice finer details such as surface mottling.
NGC 185 is best seen from the Northern Hemisphere latitudes during the months of October, November and December.
NGC 185 Data Table
|Object Type||Dwarf Spheroidal Galaxy|
|Distance (light-years)||2.0 Million|
|RA (J2000)||00h 38m 58s|
|DEC (J2000)||+48d 20m 27s|
|Apparent Size (arc mins)||11.4 x 10.0|
|Notable Feature||Satellite galaxy of the Andromeda Galaxy (M31)|