A dark galaxy is a hypothesized galaxy with no, or very few, stars. They received their name because they have no visible stars,[1]but may be detectable if they contain significant amounts of gas. Astronomers have long theorized the existence of dark galaxies, but there are no confirmed examples to date.[2] Dark galaxies are distinct from intergalactic gas clouds caused by galactic tidal interactions, since these gas clouds do not contain dark matter, so they do not technically qualify as galaxies. Distinguishing between intergalactic gas clouds and galaxies is difficult; most candidate dark galaxies turn out to be tidal gas clouds.[3] The best candidate dark galaxies to date include HI1225+01,[4] AGC229385,[5] and numerous gas clouds detected in studies of quasars.
On 25 August 2016, astronomers reported that Dragonfly 44, an ultra diffuse galaxy (UDG) with the mass of the Milky Way galaxy, but with nearly no discernable stars or galactic structure, is made almost entirely of dark matter.[6][7][8]
https://en.wikipedia.org/wiki/Dark_galaxy
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