Effect due to gravitational bending of light by mass concentrations which results in (1) the strong distortion of background Concentration of 106 to 1012 stars, dust and gas, that are gravitationally bound. Our galaxy contains ~2 × 1011 stars. There are four main types of galaxies: • Elliptical • Lenticular • Spiral • Irregular Click on Term to Read More images (arcs) behind some massive foreground galaxy clusters, and (2) multiple images of the same background quasar behind a foreground galaxy. Over 50 lensed quasi-stellar objects are known.
Image source: http://www.centauri-dreams.org/wp-content/uploads/2006/05/lensed_quasar_2.jpg.