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Gravitational Lensing

### What is Gravitational Lensing?

Gravitational lensing, loosely speaking, refers to the fact that
light rays from a distance source are deflected and distorted by
intervening mass distributions. Gravitational lensing is commonly
divided into three areas. All these have important implications
for the dark matter problem, galaxy structures and cosmology.
The first is the so-called strong gravitational
lensing, where a single background source is distorted into
multiple
images , spectacular giant arcs, as in
CL2244
and A2218 (shown above), and, in some cases even complete
rings .

The second area is gravitational microlensing, where we observe the
time-changing magnification of a background source due to lensing,
please refer to my brief
introduction elsewhere.

The third lensing pheonomenon is the so-called weak lensing, where we
see the weak distortions of many distant background galaxies by
intervening matter. The effect is weak, but ubiquitous, and hence has
very diverse applications in astrophysics.

### Some Groups Working on Gravitational Lensing

For groups working on microlensing, see my introduction on
microlensing
### Literature on Gravitational Lensing

To learn more about lensing, I recommend the following reviews:
- Blandford, R. & Narayan, R. 1992,
"Cosmological applications of gravitational lensing",
Annual Review of Astronomy and Astrophysics, 30, 311

- Narayan, R. & Bartelmann, M. 1997,
in: Proceedings of the 1995 Jerusalem Winter School, eds. A. Dekel
and J.P. Ostriker, also available as a
preprint

- For updated chapters in the book by Schneider, Ehlers & Falco, see
Peter Scheider's
site

- A. Pospieszalska-Surdej, J. Surdej and A. Detal complied a very complete
bibliography

This page is under construction. Last updated on Nov. 17, 1999.