What is a Gravitational Lens?
Recall that gravity bends light. For this reason, gravity can act as a sort of a lens, distorting the light from a distant star or galaxy. One thing this can do is to increas the total amount of light from the distant source that reaches the Earth. If the bending is enough, we could get two images of a distant point source of light. Cnsider a very distant light source that is not a point but is spread out, like a galaxy. Consider a very distant galaxy or group of galaxies that lies between us and the light source and acts as a strong bending object. Then we can get a distorted image. This really happens.
Predicted by Einstein’s theory of general relativity, gravitational lenses are collections of matter (such as clusters of galaxies) that are so massive they warp space in their vicinity, allowing the light of even more-distant objects to curve around the central lens-mass and be seen from Earth as magnified objects.
The physical principle behind a gravitational lens (also known as a cosmic mirage ) has been known since 1916 as a consequence of Einstein’s General Relativity Theory. The gravitational field of a massive object curves the local geometry of the Universe, so light rays passing close to the object are also curved (in the same way as a `straight line’ on the surface of the Earth is necessarily curved because of the curvature of the Earth’s surface). This effect was first observed by astronomers in 1919 during a total solar eclipse. Accurate positional measurements of stars seen in the dark sky near the eclipsed Sun indicated an apparent displacement in the direction opposite to the Sun, about as much as predicted by the theory. The effect was obviously due to the gravitational attraction of the stellar photons when they passed near the Sun on their way to us. This was a direct confirmation of a new phenomenon and represented a milestone in physics. In the 1930’s, astronomer Fritz Zwicky (
The gravitational lens is an astronomical phenomenon observed when a massive object, like a cluster of galaxies or a black hole, bends light from a very distant light source, such as a quasar (young and bright galaxy). This occurs due to the gravitational warping of space-time first described by Albert Einstein in his general theory of relativity. It is called a gravitational lens by analogy to a conventional lens. Both can bend light, but in this case the mechanism is very different — rather than bending light using curved matter, in this case the space-time itself is being curved. Gravitational lensing can cause distant quasars to appear in locations where they don’t really exist. Because the light is bent in the gravity well of a massive object, the apparent location deviates from the actual location. Gravitational lenses can also cause multiple images of a quasar to appear in the sky — light is bent around the massive object in both directions, thereby producing the multiple imag
Find a Web picture that shows an image of a gravitational lens and report the address of the web page. • Galaxies frequently run into each other and have a tidal interaction. You will use a computational engine to model two interacting galaxies to see if you can reproduce the observed morphology of two real systems. This applet is doing calculations in your browser concerning the gravitational interaction between galaxies. You can twiddle the dials with left or right mouse button to change orientations. You can change mass ratios and distances of closest approach (peri parameter). You can choose to have a big dark matter halo around the galaxies or not (that’s the Big Halo box). Your mission is to see if you can produce a simulation that looks like the real system below which is loaded as a background image in the engine. When the colored dots more or less overlap with the image, you can consider that a reasonably good model. Record the parameters of that simulation and the time (in mi
