Chandra Quasar Twins (Optical & X-ray)
Credit: NASA/SAO/CXC/P.Green et al.

The Universe Gets Slightly Less Interesting

According to Einstein, matter bends light. Astronomers have found that large distributions of mass can act like a "gravitational lens" to bend light from background galaxies, forming two (or more) identical images of the same object. A pair of distant active galaxies, Q2345+007 A & B, were thought to be identical images formed by such a "gravitational lens", but they were thought to be an especially unusual case, since there was no discernible foreground cluster of galaxies seen in optical images to provide the mass for the lens. Astronomers suggested that the "foreground lens" might be a weird distribution of galaxies, an invisible "dark cluster" possessing lots of gas but few stars. Such a "dark cluster" should be bright in X-rays. But a recent observation by the Chandra X-ray Observatory put an end to this speculation. The image above shows an optical image of the quasar pair, while the inset in the lower right shows the Chandra X-ray image. Chandra did not detect any evidence of a large foreground distribution of mass; in addition the X-ray spectra of the two quasars are surprisingly different. Both pieces of evidence suggest that the two quasars are actually individual objects. Astronomers now suspect that these two objects were formed by a collision of galaxies when the universe was much smaller and galaxies much closer together. Come to think of it, that's actually pretty interesting.

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Page Author: Dr. Michael F. Corcoran
Last modified June 21, 2002