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Astronomers using the Hubble Space Telescope and the Very Large Telescope have made precise tests of general relativity on galactic scales. The nearby galaxy ESO 325-G004 acts as a strong gravitational lens, distorting light from a distant galaxy behind it to create an Einstein ring around its centre. By comparing the mass of ESO 325-G004 (from ...
Lenard pointed to the 1801 prediction that Johann Georg von Soldner had derived from Newtonian gravity for starlight bending around a massive object, [31] which corresponds to half the general-relativistic prediction derived by Einstein in 1915, and thus to Einstein's own earlier derivation of 1911, and claimed that it proved Einstein to be a ...
Einstein cross: four images of the same astronomical object, produced by a gravitational lens. The deflection of light by gravity is responsible for a new class of astronomical phenomena. If a massive object is situated between the astronomer and a distant target object with appropriate mass and relative distances, the astronomer will see ...
The amount of gravitational lensing is described by Albert Einstein's general theory of relativity. [ 1 ] [ 2 ] If light is treated as corpuscles travelling at the speed of light , Newtonian physics also predicts the bending of light, but only half of that predicted by general relativity.
Gravitational lensing's modern theoretical framework was established with works by Yu Klimov (1963), Sidney Liebes (1964), and Sjur Refsdal (1964). [1] Gravitational lensing was first observed in 1979, in the form of a quasar lensed by a foreground galaxy.
General relativity also predicts novel effects of gravity, such as gravitational waves, gravitational lensing and an effect of gravity on time known as gravitational time dilation. Many of these predictions have been confirmed by experiment or observation, while others are the subject of ongoing research.
For a source right behind the lens, θ S = 0, the lens equation for a point mass gives a characteristic value for θ 1 that is called the Einstein angle, denoted θ E. When θ E is expressed in radians, and the lensing source is sufficiently far away, the Einstein Radius , denoted R E , is given by
In weak lensing by large-scale structure, the thin-lens approximation may break down, and low-density extended structures may not be well approximated by multiple thin-lens planes. In this case, the deflection can be derived by instead assuming that the gravitational potential is slowly varying everywhere (for this reason, this approximation is ...