Tear in Andromeda's spiral

Andromeda, Spiral Galaxy M81
Image: Subaru Telescope (NAOJ), Hubble Space Telescope;
Processing & Copyright: Roberto Colombari & Robert Gendler

If you look at the outer spiral above the galactic center you clearly see a tear in this magnificent island of stars. Astronomers explain it as the result of a galactic collision where a smaller galaxy in the Local Group caused the break of the spiral.

Study of space depends on what we humans can see at various wavelengths of light using our optical and other instruments. Hubble Space Telescope has raised the level of imagery and information the photos reveal to observes to an entirely new level.

For other details in this portrait of Andromeda check the explanation given for this photo in the APOD site.