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There is another theory as to the formation of these. It involves (relatively) sudden and short-lived influxes of matter into galaxies' central black holes, creating "flashes"of light and other energy that travel outwards as spheres, appearing, of course as circles. There are still some issues with this explanation, which is why I've put this comment here, rather than into the body of the article.
Andromeda galaxy contrasted and recolored[1] (some few afar stars are montaged)
Include the Circumgalactic Medium
The CGM has been found to play a substantial role in a Galaxy's life (star formation) since it contains the same if not more baryonic matter than the host galaxy and thus will govern the galaxy's accretion of new matter. (https://arxiv.org/abs/1903.05644) For this reason, adding a note about the CGM should be pertinent to this article. For example, in the "Spirals" section it is stated that "Though the stars and other visible material contained in such a galaxy lie mostly on a plane, the majority of mass in spiral galaxies exists in a roughly spherical halo of dark matter which extends beyond the visible component, as demonstrated by the universal rotation curve concept." and a simple change could be "Though the stars and other visible material contained in such a galaxy lie mostly on a plane, the majority of mass in spiral galaxies exists in a roughly spherical halo of dark matter which extends beyond the visible component, this reservoir of baryonic matter is known as the Circumgalactic Medium, as demonstrated by the universal rotation curve concept." What are other people's thoughts on this?
The CGM plays a vital role in both galaxy and stellar evolution. While a section should be added to the galaxy page, it is such a vast and diverse subject (for example, see https://arxiv.org/abs/1709.09180) that it really should get its own page. At this time, Googling the circumgalactic medium returns mostly scientific articles. Having a page to introduce the main ideas to newcomers within the field would be beneficial.
The article states that the Milky Way has a diameter of 'at least 30,000 PS or 100,000 LY, when the most recent research (shown on the Milky Way page as 185,000 LY +/- 15,000 LY) lists a diameter of roughly 60,000 PS or 190,000 LY. I would have edited that, however the article is locked.
Galaxy
What is galaxy 122.177.107.184 (talk) 02:34, 20 March 2022 (UTC)[reply]