What is a Gravitational Lens?

Convergent or multiple imaging effects of gravitational field sources on electromagnetic radiation emitted by celestial bodies located behind it. It is named because of its converging effect like a convex lens. The gravitational lensing effect is a phenomenon predicted by Albert Einstein's general theory of relativity. Because space-time will be distorted near a large-mass celestial body, the light will bend near the large-mass celestial body (light propagates along the short-distance line of curved space ), So that the observer can see the light source blocked in space by a massive celestial body [1] . If there is a large foreground celestial body in the line of sight from the observer to the light source, two images will be formed on both sides of the light source, as if a lens is placed between the observer and the celestial body. This phenomenon is called gravity Lens effect. The observation of the effect of gravitational lensing proves that Albert Einstein's general theory of relativity is indeed a correct description of gravity.

Gravitational lens

Gravitational lens effect, English name: Gravitational lens effect, according to
The gravitational lens can brighten the background celestial body. On the other hand, the background celestial body can also act as a flashlight to "illuminate" the intermediate celestial body.
In astronomy research, people are generally used to classify the phenomenon of gravitational lensing into strong and weak. Interestingly, the classification criteria are not very strict.
There are two kinds of celestial bodies involved in a gravitational lens phenomenon. One is a distant celestial body that is equivalent to a candle in a lens test. of
Gravity lenses are divided into strong and weak, to a large extent they are seen with the eyes. The distortion that can be seen from the image of a background celestial body is strong. What is invisible is weak. This sentence actually needs further explanation. What you can see is actually more extreme. For example, the galaxy is stretched into strips.
Researchers at the University of Nottingham, Indianapolis have observed the first moon of the exoplanet through gravitational lens technology, but we cannot further determine its authenticity because of limited observational techniques. [7]

Gravitational lens abroad

Previously, the strong gravitational lens systems found internationally were very scarce, and a total of about 120 galaxy clusters showed strong gravitational lens systems. Ph.D. student Wen Zhonglue et al. Of the National Astronomical Observatory selected nearly 40,000 galaxy clusters based on the data of SDSS surveys in the United States. By carefully examining the images of each galaxy cluster, 13 new galaxy cluster strong gravitational lens system candidates were found. Among them, 4 cases are definitely gravitational lens systems with almost no confirmation, 5 are very likely gravitational lens systems, and 4 are very likely gravitational lens systems. In two of them, a gravitational lens halo was created because the background galaxy and the foreground galaxy cluster were almost on the same line of sight! This is an extremely rare treasure. The work was published as a newsletter in the first issue of Research in Astronomy and Astrophysics 2009. [8]

Gravitational lens domestic

Chinese young astronomer discovers rare arc of gravitational lensing [8]
According to the website of the Chinese Academy of Sciences, Wen Zhonglue, a PhD student from the National Astronomical Observatory, discovered the strong gravitational lens system of galaxy clusters from the international survey database SDSS. This is the first time that a Chinese scholar has discovered the phenomenon of gravitational lenses from observation data. [8]
Chinese astronomers have theoretically studied the effect of gravitational lensing and its application in cosmology, and have won the second prize of the National Natural Science Award.
Gravitational lens
The team performed numerical simulations to study the frequency of their occurrence and to study the nature of the large-scale structure of the universe. This work by Wen et al. Is the first time that Chinese astronomers have directly discovered the arc of gravitational lensing from observational data. After the paper was submitted and published online, it immediately aroused great interest from similar groups in the United Kingdom and the United States. Interviews with the British team revealed that 5 cases overlapped with the candidates they found and were therefore independent findings. The US team also published their results a few days later and confirmed two cases in our sample with spectral observations. China cannot perform spectral verification due to the lack of large telescopes. Nevertheless, Dr. Mao Shude, a well-known gravitational lens expert from the University of Manchester in the UK, believes this is a new and exciting discovery made from a large number of survey databases. He specially wrote news commentary for the publication of this article in the RAA. [8]

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