 
					
					
						Gravitational Lensing					
				 
				
					
						 المؤلف:  
						Diane Fisher Miller
						 المؤلف:  
						Diane Fisher Miller					
					
						 المصدر:  
						Basics of Radio Astronomy
						 المصدر:  
						Basics of Radio Astronomy					
					
						 الجزء والصفحة:  
						p45
						 الجزء والصفحة:  
						p45					
					
					
						 28-2-2016
						28-2-2016
					
					
						 1980
						1980					
				 
				
				
				
				
				
				
				
				
				
			 
			
			
				
				Gravitational Lensing
Einstein’s theory of general relativity predicts that space is actually warped around massive objects.
In 1979, astronomers noticed two remarkably similar quasars very close together. They had the same magnitude, spectra, and red shift. They wondered if the two images could actually represent the same object. It turned out that a galaxy lay directly in the path between the two quasars and Earth, much closer to Earth than the quasars. The geometry and estimated mass of the galaxy were such that it produced a gravitational lens effect that is, a warping of the light as it passes through the space around the galaxy.

Many other instances of gravitational lensing have now been detected. Gravitational lensing can produce more than two images, or even arcs. Images produced by point-like gravitational lenses can appear much brighter than the original source would appear in the absence of the gravitational lens.
				
				
					
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