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Light Deflection 2b
Joachim Wambsganss
Department of Astrophysical Sciences, Princeton
According to Einstein's Theory of Gravity, a ray of light is attracted by a clump of matter. As a consequence of "gravitational lensing," the light ray changes its direction from a straight line by a minute amount when it passes close to a cosmic object. Stars and planets in our Milky Way or in other galaxies can act as "microlenses": They focus the light of a background source in a very characteristic way. The main effect is a time-variable magnification of the background source due to relative motion.In our research, we simulate the effects of light deflection by tracing light rays backward through a field of lensing objects and calculating their deflection. The colors in the resulting two-dimensional maps in the "source plane" reflect the density of light rays, and they indicate the magnification of the background source as a function of its position. The sharp "caustic lines" are locations of very high magnification. When a background star moves across such a pattern, we can measure its variable brightness with our telescopes and deduce properties of dark matter or discover extrasolar planets.
This microlensing pattern indicates the magnification of a background star as a function of its position, produced by the light deflection of an intervening star with three planets. The relative separations of the planets are 1.618, 1.000 and 0.618. These distances define the "lensing zone", the region of maximum effect. These numbers reflect the "golden ratio", which is no accident, since the mathematical structure of the underlying lens equation is the same: x - 1/x = 1. |
