NGC 185 (also known as Caldwell 18) is a dwarf spheroidal galaxy located 2.08 million

light-year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...

s from Earth, appearing in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the e ...

Cassiopeia. It is a member of the Local Group, and is a satellite of the Andromeda Galaxy (M31). NGC 185 was discovered by William Herschel on November 30, 1787, and he cataloged it "H II.707".

John Herschel Sir John Frederick William Herschel, 1st Baronet (; 7 March 1792 – 11 May 1871) was an English polymath active as a mathematician, astronomer, chemist, inventor, experimental photographer who invented the blueprint and did botanical wor ...

observed the object again in 1833 when he cataloged it as "h 35", and then in 1864 when he cataloged it as "GC 90" within his '' General Catalogue of Nebulae and Clusters''. NGC 185 was first photographed between 1898 and 1900 by James Edward Keeler with the Crossley Reflector of

Lick Observatory The Lick Observatory is an astronomical observatory owned and operated by the University of California. It is on the summit of Mount Hamilton, in the Diablo Range just east of San Jose, California, United States. The observatory is managed by th ...

. Unlike most dwarf elliptical galaxies, NGC 185 contains young stellar clusters, and star formation proceeded at a low rate until the recent past. NGC 185 has an active galactic nucleus (AGN) and is usually classified as a type 2

Seyfert galaxy Seyfert galaxies are one of the two largest groups of active galaxies, along with quasars. They have quasar-like nuclei (very luminous, distant and bright sources of electromagnetic radiation) with very high surface brightnesses whose spectra ...

, though its status as a Seyfert is questioned. It is possibly the closest Seyfert galaxy to Earth, and is the only known Seyfert in the Local Group.

Distance measurements

At least two techniques have been used to measure distances to NGC 185. The surface brightness fluctuations distance measurement technique estimates distances to galaxies based on the graininess of their appearance. The distance measured to NGC 185 using this technique is 2.08 ± 0.15 Mly (640 ± 50 kpc). However, NGC 185 is close enough that the tip of the red giant branch (TRGB) method may be used to estimate its distance. The estimated distance to NGC 185 using this technique is 2.02 ± 0.2 Mly (620 ± 60 kpc).

Star formation

Martínez-Delgado, Aparicio, & Gallart (1999) looked into the

star formation Star formation is the process by which dense regions within molecular clouds in The "medium" is present further soon.-->interstellar space

history of NGC 185 and found that the majority of star formation in NGC 185 happened at early times. In the last ~1 Gyr, stars have formed only near the center of this galaxy. Walter Baade discovered young blue objects within this galaxy in 1951, but these have turned out to be star clusters and not individual stars. A supernova remnant near the center was also discovered by Martínez-Delgado et al.

References

External links

* {{DEFAULTSORT:NGC 0185 Dwarf galaxies Dwarf elliptical galaxies Dwarf spheroidal galaxies Local Group Andromeda Subgroup Cassiopeia (constellation) 0185 00396 02329 018b 17871130

Distance measurements

Star formation

See also

References

External links