... Tonight's Sky . ... Gravitational wave search provides insights into galaxy evolution and mergers . ... galaxies . ... Astronomers discover quasars acting as gravitational lenses . Gravitational lensing candidates are invaluable for estimating the mass of a quasarт??s host galaxy. ... Astronomers using NASAт??s Hubble Space Telescope have found several examples of galaxies containing quasars, which act as gravitational lenses, amplifying and distorting images of galaxies aligned behind them. ...