Massive objects such as clusters of galaxies bend space in their vicinity, distorting and in some cases magnifying the objects behind them. This interesting effect is called gravitational lensing.
Gravitational lenses are being used to study young galaxies
and to gain a better understanding of the total amount of
matter in the universe. Hubble's observations of gravitational
lenses show that the lensing clusters must have more matter
than meets the eye.
image shows "ghost" images of a single, distant galaxy. It
lies far beyond the cluster that fills the frame. The multiple,
distorted images are produced by the cluster's strong gravitational
field, which bends passing light beams like a lens.