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Gravitational lensing

Gravitational lensing occurs when massive objects in space bend light from distant sources, similar to how a glass lens bends light. According to Einstein's theory of general relativity, matter like galaxy clusters can curve spacetime around them, causing light rays to change direction as they pass by. This effect matters for several reasons: it allows astronomers to study distant galaxies that would otherwise be too faint to observe, helps map the distribution of dark matter in the universe, and provides a way to test predictions of general relativity. Gravitational lensing comes in three forms: strong lensing creates multiple distorted images or bright rings, weak lensing causes subtle distortions detectable only by analyzing many galaxies statistically, and microlensing causes brightness changes in objects over time.

Sources

• en.wikipedia.org: “A gravitational lens is matter, such as a cluster of galaxies or a point particle, in sufficient quantity and density to bend light noticeably from a distant source as it travels toward an observer.”
• en.wikipedia.org: “The amount of gravitational lensing is described by Albert Einstein's general theory of relativity.”
• en.wikipedia.org: “There are three classes of gravitational lensing: Strong lensing Where there are easily visible distortions such as the formation of Einstein rings, arcs, and multiple images.”
• en.wikipedia.org: “Weak lensing Where the distortions of background sources are much smaller and can only be detected by analyzing large numbers of sources in a statistical way to find coherent distortions of only a few percent.”