The Andromeda Deep Field

Explanation: What can you learn from looking into the depths of space? In an effort to find out true ages of stars in neighboring Andromeda galaxy 's halo , astronomers stared into the galaxy giant with the new Advanced Camera for Surveys through the Hubble Space Telescope . The resulting exposure of over three days, shown above , is the deepest exposure in visible light ever taken, although shorter in duration than the multi-wavelength effort toward the Hubble Deep Field . The final image illuminated not only Andromeda (M31) but the distant universe. Andromeda's halo stars turned out to be have a wider range of ages than our Milky Way 's halo stars, likely indicating more encounters with small neighboring galaxies . Visible on the above left is one of Andromeda's globular star clusters , while literally thousands of background galaxies are seen in the distance universe , far beyond M31.