Strong gravitational lensing is a gravitational lensing effect that is strong enough to produce multiple images, arcs, or even Einstein rings. Generally, the strong lensing effect requires the projected lens mass density greater than the critical density . For point-like background sources, there will be multiple images; for extended background emissions, there can be arcs or rings. Topologically, the multiple image production is governed by the odd number theorem.
Read more about Strong Gravitational Lensing: Galaxy Lensing, Cluster Lensing
Famous quotes containing the word strong:
“The fate of the country does not depend on how you vote at the polls,—the worst man is as strong as the best at that game; it does not depend on what kind of paper you drop into the ballot- box once a year, but on what kind of a man you drop from your chamber into the street every morning.”
—Henry David Thoreau (1817–1862)