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The process is known as gravitational lensing, and was one of the predictions made by Einstein's general relativity.
In a gravitational lens, the gravity from the massive object bends light as a lens might. As a result, the path of the light from the source is curved, distorting its image. For example, the apparent location of the source to the observer may be different from its actual position. In addition, the observer may see multiple images of a single source. If the source, massive object, and the observer lie on a line, the source will appear as a ring behind the massive object. This image is known as an Einstein ring. More commonly, the massive galaxy is off-center, creating different numbers of images according to the relative positions of the source, lens, and observer, and the shape of the gravitational well of the lensing galaxy.
There are three classes of gravitational lensing:
Gravitational lenses act on all kinds of electromagnetic radiation, not just visible light. Weak lensing effects are being studied for the cosmic microwave background and strong lenses have been observed in radio and X-ray regimes as well.
According to general relativity, gravitational fields "warp" space-time and therefore bend light as a result. This theory was confirmed in 1919 during a solar eclipse, when Arthur Eddington observed the light from stars passing close to the sunThe Sun (also called Sol is the star in our solar system. Planet Earth orbits the Sun. Other bodies that orbit the Sun include other planets, asteroids, meteoroids, comets and dust. Not all objects passing through the solar system have been orbitally capt was slightly bent, so that stars appeared slightly out of position.
Einstein realized that it was also possible for astronomical objectSolar system Extrasolar objects Simple objects Compound objects Extended objects Sun Planets Mercury Venus Earth Moon Mars Phobos Deimos Jupiter satellites Saturn satellites Uranus satellites Neptune satellites Pluto Charon Asteroids Near-Earth asteroidss to bend light, and that under the correct conditions, one would observe multiple images of a single source, called a gravitational lens or sometimes a gravitational mirage. However, as he only considered gravitational lensing by single stars, he concluded that the phenomenon would most likely remain unobserved for foreseeable future. In 1937, Fritz ZwickyFritz Zwicky ( February 14 1898 February 8 1974) was a Swiss astronomer, born in Varna, Bulgaria to Swiss parents. In 1925 he came to the California Institute of Technology in the United States and remained there for the rest of his life, though he remain first considered the case where a galaxy could act as a lens, something that according to his calculations should be well within the reach of observations.
It was not until 1979 that the first gravitational lens would be discovered. It became known as the "Twin Quasar" since it initially looked like two identical quasars; it is officially named Q0957+561. This gravitational lens was discovered accidentally by Dennis WalshDenis Walsh is a British astronomer, b. 1933 into a poor family in Manchester, England. He developed an early aptitude for mathematics and physics, gaining his doctorate from Manchester University at the age of 19. He married Pamela Lawton in 1958 by whom, Bob Carswell , and Ray Weymann using the Kitt Peak National ObservatoryThe Kitt Peak National Observatory KPNO is located on a 6,875 ft peak of the Quinlan Mountains in the Arizona- Sonoran Desert on the Tohono O'odham Nation, 55 miles southwest of Tucson. The observatory is considered to be part of the National Optical Astr 2.1 meter telescopeNice Observatory. A telescope is perhaps the most important astronomical tool; such technology gathers (and focuses) electromagnetic radiation. Telescopes increase the apparent angular size of objects, as well as their apparent brightness. Galileo Galilei.
The study of gravitational lenses is an important part of the future of astronomy and astrophysics.