How Did the Milky Way Get Its Spiral?

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Most galaxies that we know of are spirals, including the Milky Way, but how do they form and keep their shape over billions of years?

Hosted by: Hank Green

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Sources:
https://earthsky.org/space/how-do-spiral-galaxies-keep-their-shape
https://astronomy.swin.edu.au/cosmos/S/Spiral+Galaxy+Formation
https://www.nasa.gov/feature/how-to-shape-a-spiral-galaxy
http://web.cn.edu/jburton/Astronomy/formationofMilkyWay.htm
https://www.scientificamerican.com/article/what-process-creates-and/
https://www.scientificamerican.com/article/how-did-scientists-determ/
https://arxiv.org/abs/1608.00969
http://www.sci-news.com/astronomy/magnetic-fields-spiral-galaxies-07894.html
https://arxiv.org/abs/1907.06648
https://www.eso.org/sci/meetings/2015/Rainbows2015/Talk_Files/DAY3/WeggC.pdf
http://articles.adsabs.harvard.edu/pdf/1964ApJ...140..646L

Images:
https://hubblesite.org/science/galaxies
https://esahubble.org/images/heic0910i/
https://svs.gsfc.nasa.gov/13155
https://beltoforion.de/en/spiral_galaxy_renderer/
https://www.nasa.gov/feature/how-to-shape-a-spiral-galaxy
https://esahubble.org/images/heic1202a/
https://esahubble.org/images/heic2002a/
https://simple.wikipedia.org/wiki/File:Morgan-Keenan_spectral_classification.png
https://esahubble.org/images/heic0910s/
https://esahubble.org/images/opo0501a/
https://esahubble.org/images/potw1801a/
https://esahubble.org/images/heic1107a/