Hubble’s Inside the Image: Lensed Supernova Refsdal - YouTube - NASA Goddard - astrophysics

Albert Einstein predicted gravitational lensing,the warping of spacetime by the gravitational pull of massive objects such as galaxies.Gravity is actually a curvature in spacetime and can have the effect of enabling observation of very distant objects.This can also be used to ascertain how fast the universe is expanding.

Supernova explosion 4 billion light-years away revealed using gravitational lensing - astrophysics

Gravity from massive objects such as a galaxy causes light from the original light source to bend,an effect predicted by Einstein's Theory of General Relativity.This results in a magnifying effect,revealing objects we cannot see even with a powerful telescope.In this case,the image of the original light source was in a form called Einstein's cross.