There are enough solar systems within a single galaxy to keep scientists busy for a long time — studying, observing and imagining. (Our own galaxy may contain as many as 400 billion stars.) But as we strive to view the rest of the universe, we discover that our Milky Way galaxy is just one among at least 170 billion galaxies in the observable universe.
It's difficult not to feel small yet wondrous at the thought of such vast amounts of unexplored space. To spark some of that wonder, here are 15 of the Hubble Space Telescope's best images of other galaxies.
Barred Spiral Galaxy NGC 1300:
Antennae Galaxies NGC 4038-4039:
Backward-spinning Spiral Galaxy NGC 4622:
All photos: NASA and the Hubble Heritage Team via hubblesite.org