Scientists think they've finally solved the decades-long mystery of why our Milky Way galaxy is so rare

• Spiral galaxies like the Milky Way are surprisingly rare in our galactic neighborhood.
• Astronomers have wondered why for years, and now they may have an answer.
• Researchers simulated the evolution of our cosmic neighborhood and discovered a violent past.

Galaxies come in many shapes and sizes. The Milky Way, for example, is a spiral galaxy because of the way that stars, dust, and gas spiral out from the center of the galaxy.