More than a millennia ago, Andromeda was described as a small, patchy cloud occupying a section our the night sky. Flash forward to 1887, when English astronomer Isaac Roberts took the first long-exposure image of the “Andromeda Nebula,” revealing it is not a nebula at all, but a large, bustling galaxy with billions upon billions of stars. Surely Abd al-Rahman al-Sufi (an Iranian scientists who was likely the first person to know of Andromeda’s existence), Charles Messier, and Roberts himself would be astonished that we can now resolve individual stars and see its halo.
In a new study, after analyzing Andromeda’s disk, and looking at the motions’ of multiple populations of stars, researchers have learned that there is stark contrast between its disk and the Milky Way. This ultimately tells the tale, that Andromeda’s past was more turbulent than we previously believ...
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