Hubble sights distortions from gravitational 'lenses'
May 14, 1999
(CNN) -- The idea that images could be highly magnified by gravity from massive objects was suggested by Albert Einstein more than six decades ago. Now, the Hubble Space Telescope has uncovered exotic patterns, rings, arcs and crosses that astronomers believe are optical mirages produced by such "lenses," nature's equivalent of having giant magnifying glasses in space.
A gravitational lens is created when the gravity of a massive foreground object, such as a galaxy or black hole, bends the light coming from a far more distant galaxy directly behind it, according to astronomers at the Space Telescope Science Institute. This focuses the light to give multiple or distorted images of the background object as seen by the observer.
A look at over 500 Hubble fields of sky has uncovered 10 interesting lens candidates in the deepest 100 fields, the STSI said. This is a significant increase in the number of known optical gravitational lenses. Hubble's sensitivity and high resolution allow it to see faint and distant lenses that cannot be detected with ground-based telescopes whose images are blurred by Earth's atmosphere.
An analysis of this "Top Ten" list of Hubble gravitational lenses is published by Kavan Ratnatunga and Richard Griffiths of Carnegie Mellon University in the May issue of the Astronomical Journal.
Hubble's ability to see so many of these lenses in a small fraction of the sky takes them from being a scientific curiosity to serving as a potentially powerful tool for probing the universe's evolution and expansion, astronomers said.
In 1936 Einstein computed the gravitational deflection of light by massive objects and showed that an image can be highly magnified if the observer, source and the lensing object are well aligned. However, the lensed image separations were predicted to be so small in angular size, Einstein knew they were beyond the capabilities of ground-based optical telescopes. This made him remark that "there is no great chance of observing this phenomenon."
It wasn't for another 40 years since Einstein's conclusion that the first gravitational lens was discovered in 1979. Several bright and nearby lenses have been discovered since then from ground-based observations.
Net tool key to Hubble project
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