Messier 110, or M110, also known as NGC 205, is a dwarf elliptical galaxy that is a satellite of the Andromeda Galaxy in the Local Group.[8]
Early observational history
Charles Messier never included the galaxy in his list, but it was depicted by him, together with M32, on a drawing of that, more recently known as the Andromeda Galaxy (the latter descriptor not being in use for such objects in that century); the label of the drawing evinces that Messier first saw the object in 1773.[a][9] The galaxy was independently discovered by Caroline Herschel on August 27, 1783; her brother William Herschel described her discovery in 1785.[b][9][10] The suggestion to assign the galaxy a Messier number was made by Kenneth Glyn Jones in 1967,[11] making it the last member of the Messier List.
Properties
This galaxy has a morphological classification of pec dE5, indicating a dwarf elliptical galaxy with a flattening of 50%. It is designated peculiar (pec) due to patches of dust and young blue stars near its center.[12] This is unusual for dwarf elliptical galaxies in general,[8] and the reason is unclear.[12] Unlike M32, M110 lacks evidence for a supermassive black hole at its center.[13]
The interstellar dust in M110 has a mass of (1.1–1.8)×104 M☉ with a temperature of 18–22 K, and the interstellar gas has (4–7)×106 M☉. The inner region has sweeping deficiencies in its interstellar medium IM, most likely expelled by supernova explosions. Tidal interactions with M31 may have stripped away a significant fraction of the expelled gas and dust, leaving the galaxy as a whole, as it presents, deficient in its IM density.[14]
Novae have been detected in this galaxy, including one discovered in 1999,[15] and another in 2002. The latter, designated EQ J004015.8+414420, had also been captured in images taken by the Sloan Digital Sky Survey (SDSS) that October.[16]
Local context
About half of the Andromeda's satellite galaxies are orbiting it along a highly flattened plane, with 14 out of 16 following the same sense of rotation. One theory proposes that these 16 once belonged to a subhalo surrounding M110, then the group was broken up by tidal forces during a close encounter with Andromeda.