Think about the grandest objects you’ve ever seen pictures of in the night sky. Sure, there are a whole slew of targets to choose from, including dying stars, supernova remnants, star-forming nebulae and clusters of stars both new and old, but nothing compares to the beauty of a spiral galaxy. Containing between billions and trillions of stars, these “island universes” display a unique structure all their own. A structure, mind you, that’s puzzling if you think about it, as our questioner Greg Rogers did:

One thing that has always bothered me about spiral galaxies is that you only see the arms wrapping around about half-way or so. Since the outside is spinning around the core more slowly, I would expect that we should see some galaxies with arms wrapping many times around the core. Is the universe simply not old enough for these more tightly wound spiral galaxies to have formed?

You can look at any number of spiral galaxies, but they all have the same apparent structure in common.

from Forbes – Tech http://ift.tt/1THQz2j
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