A foreground galaxy of mass acts as a point gravitational lens for a distant quasar…

PHYSICS · Subjective · Fermi University Physics · Relativity & Gravitation · Schwarzschild spacetime and the tests of general relativity · Schwarzschild spacetime and the tests of general relativity

The Geometry of Gravity, Ch Orbits and light rays in Schwarzschild spacetime

Problem

A foreground galaxy of mass

M = 5\times10^{11}\,M_\odot

acts as a point gravitational lens for a distant quasar directly behind it. The lens is at distance

D_{\rm L} = 1

Gpc from Earth and the quasar is at distance

D_{\rm S} = 2

Gpc from Earth; treat the distances as Euclidean, so

D_{\rm LS} = D_{\rm S} - D_{\rm L}

. Use

GM_\odot/c^2 = 1.48

km and

1

Gpc

= 3.086\times10^{25}

m. Find the angular radius of the Einstein ring, in arcseconds.

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