Diagram illustrating how gravitational focusing makes us perceive two images of the quasar 0957+561. The quasar is at far left, Earth at far right. Fr

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Diagram illustrating how gravitational focusing makes us perceive two images of the quasar 0957+561. The quasar is at far left, Earth at far right. From Earth we see a double image of the quasar as shown on the green panel. This is because we perceive both the radiation that travels straight from the quasar to Earth & also radiation which has been bent, or focused, by the gravity of an intervening galaxy (orange spot to the left of the green panel). 0957+561, named for its celestial coordinates, was the first \double quasar\" discovered (in 1979). It is a confirmation of Einstein's general theory of relativity, which predicted the bending of light by massive objects."

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Photo credit: © DAVID PARKER/SCIENCE PHOTO LIBRARY / Alamy / Afripics
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Keywords: 0957+561, astronomy, cosmology, double, focusing, galaxy, gravitational, lens, proof, quasar, relativity, science