arc pattern you see in this Hubble image is an example of whats
known as gravitational lensing. This effect occurs when
the powerful gravitational field of a massive object--in this
case, a cluster of stars--bends, magnifies, and brightens light
emitted by much more distant objects. The magnification acts
as a powerful zoom lens to view extremely remote, ancient galaxies
not otherwise visible, boosting our understanding of their structure
and evolution. Hubble has granted astronomers their first opportunity
to study gravitational lensing, as the effect is very difficult
to detect with ground telescopes.
more about gravitational lenses and how they affect light coming
to Hubble on the Space Telescope Science institute website.