# Einstein Rings from Light Flash at Black Hole

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If an observer close to a Schwarzschild black hole fires a flash of light, some light rays return back after one revolution around the black hole. These light rays form an Einstein ring with opening angle . There are, in fact, an infinite number of Einstein rings, depending on how often the light rays orbit the black hole before they return to the observer.

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Contributed by: Thomas Müller (March 2011)

Open content licensed under CC BY-NC-SA

## Snapshots

## Details

A detailed discussion of Einstein rings from a flash of light can be found in T. Müller, "Einstein Rings as a Tool for Estimating Distances and the Mass of a Schwarzschild Black Hole," *Physical Review D*, 77(12), 2008.

## Permanent Citation

"Einstein Rings from Light Flash at Black Hole"

http://demonstrations.wolfram.com/EinsteinRingsFromLightFlashAtBlackHole/

Wolfram Demonstrations Project

Published: March 7 2011