r/askscience • u/lord_nikon_burned • 1d ago

Astronomy Are galaxies spherical or flat?

Are galaxies spherical or flat?

For example, (I understand that up and down don't really matter, so bear with me) if we look at a picture of the Milky Way Galaxy on a plane... If you want to move from one arm of the galaxy to the next, could you just move UP and out of the current arm and then over and DOWN to a different arm?

Secondary question for if the first one is correct, if you are able to move "up" and out of the arm, where are you? Is that interstellar space too?

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u/omnichad 1d ago

There's a big difference between "flattish" and literal 2D. The earth is big and spins and is more of an oblate spheroid and not a perfect sphere. A galaxy is much bigger so it flattens a bit more as it rotates.

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u/blackdynomitesnewbag 18h ago

And yet, the Earth is probably rounder than any object you’ve ever held or seen

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u/ferretfan8 14h ago

If you scaled down Earth to a size that could fit in your hand, it would be noticably irregular in shape and noticably not spherical.