An international team of astronomers, using NASA’s Fermi observatory, has made the first-ever gamma-ray measurements of a gravitational lens, a kind of natural telescope formed when a rare cosmic alignment allows the gravity of a massive object to bend and amplify light from a more distant source.
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The galaxy’s gravity bends the light into different paths, so astronomers see the background blazar as dual images. With just a third of an arcsecond (less than 0.0001 degree) between them, the B0218+357 images hold the record for the smallest separation of any lensed system known.
While radio and optical telescopes can resolve and monitor the individual blazar images, Fermi’s LAT cannot. Instead, the Fermi team exploited a “delayed playback” effect.
“One light path is slightly longer than the other, so when we detect flares in one image we can try to catch them days later when they replay in the other image,” said team member Jeff Scargle, an astrophysicist at NASA’s Ames Research Center in Moffett Field, Calif.
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Read more at: http://phys.org/news/2014-01-fermi-observatory-gamma-ray-gravitational-lens.html#jCp
Read more at: http://phys.org/news/2014-01-fermi-observatory-gamma-ray-gravitational-lens.html#jCp