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The Smithsonian Astrophysical Observatory (SAO) was established in 1890 as research unit of the Smithsonian Institution concentrating on studies of solar …
Why do galaxies differ so much in size, shape, composition and activity?
A:
Our Milky Way and the Andromeda Galaxy are giant spiral galaxies hurtling towards each other at 120 kilometers per second. In about 4 billion years, the two will meet...