Astronomers Using NASA's Hubble Discover Quasars Acting as Gravitational Lenses
Astronomers using NASA'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.
Quasars are among the brightest objects in the universe, far outshining the total starlight of their host galaxies. Quasars are powered by supermassive black holes. To find these rare cases of galaxy-quasar combinations acting as lenses, a team of astronomers selected 23,000 quasar spectra in the Sloan Digital Sky Survey (SDSS). They looked for the spectral imprint of galaxies at much greater distances that happened to align with foreground galaxies. Once candidates were identified, Hubble's sharp view was used to look for gravitational arcs and rings (indicated by the arrows in these three Hubble photos) that would be produced by gravitational lensing.