Mystery no more. Astronomers think they've figured out how spiral galaxies,
like the Milky Way, form. Credit: NASA/JPL
like the Milky Way, form. Credit: NASA/JPL
From Science Now:
Look at an image of the Milky Way galaxy, and you can't help but notice its exquisite spiral arms. For nearly 100 years, astronomers have tried to understand how the Milky Way and other spiral galaxies formed these dramatic patterns--and now they think they finally have the answer.
Current thinking about how spiral galaxies form traces back to an idea nearly 2 millennia old, to 2nd-century Egyptian mathematician Ptolemy. Trying to describe how the five planets in the night sky followed seemingly irregular paths, Ptolemy hit upon an idea he called epicycles.
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