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.

"Black Eye Galaxy" M64:

Majestic Sombrero Galaxy M104:

Barred Spiral Galaxy NGC 1300:

Hoag's Object Galaxy:

Starburst Galaxy M82:

Whirlpool Galaxy:

Dusty Spiral Galaxy NGC 4414:

Barred Spiral Galaxy NGC 1512:

Warped Edge-On Galaxy ESO 510-G13:

Antennae Galaxies NGC 4038-4039:

Grand Design Spiral Galaxy M81:

Backward-spinning Spiral Galaxy NGC 4622:

Galaxy NGC 3079:

Dusty Galaxy NGC 1316:

Overlapping spiral galaxies, 2MASX J00482185-2507365:

All photos: NASA and the Hubble Heritage Team via