SAN DIEGO — A supercluster of quasars and galaxies massed together across 600 million light years of space is the largest structure in the observable universe, astronomers say.
In a study presented Monday at the national meeting of the American Astronomical Society, researchers reported that the structure, which includes billions upon billions of stars, is believed to be 6.5 billion light years away.
"We have found nothing bigger in the (astronomy) literature, and nobody has brought to our attention anything bigger," said Gerard Williger, a researcher at the National Optical Astronomy Observatories now working at NASA's Goddard Space Flight Center in Greenbelt, Md.
When viewed from Earth, the structure is just below the center of the constellation Leo the Lion. It stretches across an expanse of the sky of two degrees by five degrees, or an area about 40 times that of the full moon as seen from Earth.
Williger said it is not known if the gathering of quasars and galaxies is bound together gravitationally or if it is a chance cluster formed by a ripple in the smooth expansion of the universe that followed the Big Bang, which is thought to have set off the formation of the universe.
"This may be an artifact of the Big Bang," he said, speculating that conditions at that point in space may have been uniquely ripe for the quick formation of stars, galaxies and quasars.
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Images: www.gsfc.nasa.gov/GSFC/SpaceSci/origins/largecluster.htm