New observations explain why Milky Way-like galaxies are For decades scientists have believed that galaxy mergers usually result in the formation of elliptical galaxies<\/a>. Now, for the the first time, researchers using ALMA and a host of other radio telescopes have found direct evidence that merging galaxies can instead form disc galaxies<\/a>, and that this outcome is in fact quite common. This surprising result could explain why there are so many spiral galaxies like the Milky Way in the Universe.<\/p>\n An international research group led by Junko Ueda, a Japan Society for the Promotion of Science<\/a> postdoctoral fellow, has made surprising observations that most galaxy collisions in the nearby Universe \u2014 within 40\u2013600 million light-years from Earth \u2014 result in so-called disc galaxies. Disc galaxies \u2014 including spiral galaxies<\/a> like the Milky Way and lenticular galaxies<\/a> \u2014 are defined by pancake-shaped regions of dust and gas, and are distinct from the category of elliptical galaxies<\/a>.<\/p>\n It has, for some time, been widely accepted that merging disc galaxies would eventually form an elliptically shaped galaxy. During these violent interactions the galaxies do not only gain mass as they merge or cannibalise each-other, but they are also changing their shape throughout cosmic time, and therefore changing type along the way.<\/p>\n Computer simulations from the 1970s predicted that mergers between two comparable disc galaxies would result in an elliptical galaxy. The simulations predict that most galaxies today are elliptical, clashing with observations that over 70% of galaxies are in fact disc galaxies. However, more recent simulations have suggested that collisions could also form disc galaxies.<\/p>\n
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