Gravitational lens: Difference between revisions

A gravitational lens magnifies and distorts very distant sources more than those only just behind the lens (and it does not distort those in front of the lens). Indeed, simple geometry can be used to calculate the efficiency of a gravitational lens as a function of the [[angular diameter distance]] to the source. If the distortion can be measured at multiple distances, this distance can be compared to the [[redshift]] of those sources: a direct [[Hubble diagram]]. Furthermore, this technique effectively requires only the ratio of the distortion at two distances. The ''total'' mass of the foreground lens therefore cancels out and does not need to be constrained (although its radial profile does). Using a more massive lens simply increases the signal to noise of the measurement.

 

 

==Historical papers and references==