This diagram illustrates a cosmic phenomenon known as gravitational lensing, in which a nearby galaxy distorts, but also magnifies a second, more distant galaxy in the background, making it appear brighter and easier to study. In the diagram, Earth is shown to the left. A foreground galaxy is shown in blue. A more distant galaxy is shown in red. The gravity of the foreground galaxy bends the light from the distant one, as shown with the lines.
The lensing effect leads to a distorted and magnified view of the distant galaxy. An example of a final image taken by ground-based telescopes is at the right, where in blue is the visible light from the foreground galaxy and in pink is the sub-millimeter wavelength emission from the background galaxy. As illustrated on the bottom, the lensing effect due to gravity can be compared to bending of light when passing through a medium of varying index of refraction, such as a glass containing water. The light bending through water results in a distorted view of the background object.
Credit: Zina Deretsky, National Science Foundation