Gravitational Lensing (GL)Currently, GL serves as a main tool in the all-important searches of Dark Matter, EXO planets etc. There is practically NO guesswork involved: The underlying framework is Einstein's highly respected
General Relativity according to which
light rays are deflected by gravity (i.e. Mass).
The nice feature is that in the limit of weak gravity the GL formalism collapses into one that is isomorphic to
Optics, with caustics and all that. Hence in practice good knowledge of Optics is sufficient for working out GL phenomena quantitatively. One of my favorite reviews (for physicists though) is by Prof. Ramesh Narayan, Harvard Univ
In
celestia.Sci, Dawoon (aka dirkpitt) and I implemented a complete framework of so-called strong, weak and micro lensing. Here is a typical rendering of a deep space configuration for strong GL:
Consider the very massive cluster of elliptical galaxies, notably NGC 6166 in the image center. The first image has Gravitational Lensing effects switched off. Then it looks like so:
[by all means click on image and then hit your browser's fullscreen key (F11 for FF)]Attachment:
n6166_noLensing.jpg [ 84.22 KiB | Viewed 1715 times ]
Now, let's switch on
GL. Explanation:
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In this display, the very massive E2 galaxy NGC 6166 is 273 Mpc (!!) away from the observer, while far behind NGC 6166 at ~420 Mpc distance is our "tiny" SBc- type Milkyway, which cannot be observed directly anymore. Milkyway, NGC 6166 and observer are approximately (but not exactly) positioned on a straight line, whence --according to GL--we expect a magnification of the tiny Milkyway into a distorted double image of the SBc-type MilkyWay, looking as follows:
[by all means click on image and then hit your browser's fullscreen key (F11 for FF)]Attachment:
n6166_Lensing.jpg [ 78.44 KiB | Viewed 1715 times ]
Bringing the MW, ngc 6166 and the observer more precisely into a straight-line configuration results in a conspicuous so-called
"Einstein circle", with the super-massive NGC 6166 located in the center. ...Indeed!
See here:
[by all means click on image and then hit your browser's fullscreen key (F11 for FF)]Attachment:
n6166_Lensing_Einstein.jpg [ 118.84 KiB | Viewed 1715 times ]
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By carefully measuring the size of the Einstein ring, we can learn something important about the system. what could that be???
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Enjoy,
Cheers,
Fridger