PHILADELPHIA -- A pillar of the big-bang theory of the creation of the universe, under increasing assault for its divergence from cosmic observations, suffered a new blow yesterday at a gathering of more than a thousand astronomers here.
Although the "cold-dark-matter" theory -- which could explain why most of the mass produced by the big bang cannot be detected -- was declared still alive by several prominent cosmologists, it was clearly cast in further doubt by results from a recently launched American-German X-ray satellite.
In the deepest X-ray images ever taken from space, the ROSAT satellite revealed a previously unknown clustering of quasars 10 billion light-years from Earth, far back toward the beginning of time.
The presence of such large-scale structures so early in the universe's evolution "is not consistent with cold-dark-matter theory," said Dr. Guenther Hasinger from Germany's Max Planck Institute for Extraterrestrial Physics.
"This may be the first glimpse of structure at this distance," he said at the 177th meeting of the American Astronomical Society. "Maybe the quasars we see aren't distributed in random fashion . . . but like the galaxies in 'great walls' and superclusters."
Superclusters are massive congregations of smaller galaxy clusters, bound together by gravity. Their discovery alerted astronomers to large-scale structuring in the universe. The "great wall" is a huge chain of galaxies stretching 500 billion light-years across the sky.
Our own Milky Way galaxy, part of a congregation of two dozen neighboring galaxies known as the "local group," appears to be moving toward some enormous, invisible mass called the "great attracter."
It was to help explain the gravitational effects causing the clustering -- and corresponding huge voids -- that prompted the cold-dark-matter theory, since an estimated 90 percent of the matter thought to exist in the universe has not been detected.
Without knowing the nature and quantity of that missing mass, cosmologists can't determine whether the universe will continue to expand forever, reach a steady state or collapse back on itself in a so-called "big crunch." Because no light or heat from the missing matter has been detected, scientists speculate that the matter is cold and dark, in the form of exotic subatomic particles with very little motion, particles as yet undiscovered.
The big-bang theory itself doesn't account for the universe's observed lumpiness, although its basic assumption that the universe began in a cataclysmic explosion has been supported by the detection of a primeval "echo" of microwave radiation at a frigid 2.7 degrees above absolute zero spread uniformly throughout the cosmos.
"It's important to distinguish the big-bang theory from the cold-dark-matter theory," said theoretical physicist Dr. Paul Steinhardt of the University of Pennsylvania. "The big bang is not in trouble."
But the cold-dark-matter theory is in trouble, because it can't explain how large-scale structures such as the "great wall" could occur as soon as 10 billion to 20 billion years after the big bang.
The quasar "clusters" observed by ROSAT are even more of a challenge to the theory, since they exhibit structure even earlier in evolutionary time than the "great wall."
They showed up as hazy blotches 15 million to 30 million light-years across in a spectacular X-ray image presented by Dr. Hasinger and Dr. Joachim Truemper, also of the Max Planck Institute.