Our Giant Universe

This detailed image features Abell 3827, a galaxy cluster that offers a wealth of exciting possibilities for study. It was observed by Hubble in order to study dark matter, which is one of the greatest puzzles cosmologists face today. Abell 3827 has been observed previously by Hubble, because of the interesting gravitational lens at its core. Looking at this cluster of hundreds of galaxies, it is amazing to recall that until less than 100 years ago, many astronomers believed that the Milky Way was the only galaxy in the universe. Gravitational lenses occur when the gravity of tremendously massive objects, such as galaxy clusters, bend and distort the light of more-distant objects behind them, making it possible to see those objects despite their distance.