Gravitational Lensing - The spacetime around a massive object (like a black hole or galaxy cluster) is so curved by the object’s gravitational field that it bends light from a background source and distorts the background object’s image x.
Abell 2218 (Galaxy Cluster)
The Cosmic Horseshoe aka LRG 3-757 x.
Einstein’s Cross aka Q2237+030 x.
Abell 1689 (Galaxy Cluster)
MACS J1206 (Galaxy Cluster)
RCS2 032727-132623 (Galaxy Cluster)
Image credits: NASA, ESA/Hubble