COBE-DMR Findings on Early Structure of Universe Confirmed

December 18, 1992

By Jeffery Kahn, [email protected]

New experimental results announced last week provide the first confirmation of the findings of structure in the infant universe made by the COBE research team headed by LBL's George Smoot.

The confirmations came during the course of the Cosmic Microwave Background Workshop held at LBL Dec. 11-12 and the Dec. 13-18 Texas/PASCOS '92 conference on the Berkeley campus. Several participants discussed new findings that are in substantial agreement with the Smoot team's discovery of fluctuations in the cosmic microwave background radiation. Scientists say that over billions of years, gravity magnified these fluctuations into the present-day structured universe.

The strongest finding of agreement came from the MIT Survey, a balloon- borne experiment involving researchers at MIT and the Goddard Space Flight Center.

"Fundamentally," said Goddard's Ed Cheng, "we have the same result as the COBE Differential Microwave Radiometer experiment. This is all the more remarkable in that the two experiments are extremely different."

Cheng and Stephan Meyer of MIT said the structures they mapped match those found by the COBE team. In terms of temperature variation, the COBE and MIT maps have been cross-correlated with 95 to 99 percent consistency. "Our data strongly supports the COBE DMR data and is strongly consistent with the DMR data," Meyer said.

The structures mapped both by COBE and the MIT experiment are inconceivably large. The maps show the structures as they existed about 100,000 years after the Big Bang.

Several scientists attending the workshop hailed the result as both the end of the decades-long era of trying to prove that large-scale structures existed in the early universe and the beginning of a new era of small-scale structure exploration. From here on, they said, the debate will shift from whether or not early structures existed to the question of the existence and evolution of individual structures.

Preliminary results from other cosmic microwave background anisotropy experiments also were announced at the workshop. The Tenerife Experiment, a ground-based exploration from a mountain in the Canary Islands, and the balloon-borne Millimeter Anisotropy Experiment (MAX), a collaboration between the Berkeley Center for Particle Astrophysics and the University of California at Santa Barbara, provide additional support for the COBE findings. Scientists emphasized, however, that these two projects are still works-in-progress.

Smoot told the workshop that his team is working on the analysis of a second year of data from the COBE DMR instrument. "Our second year of data is consistent with our first year," he said.

Smoot said his team is phasing in a new generation of analytic software. After the new software has been tested and validated, the second and third year of data from the satellite will be analyzed and the results published.

Smoot agreed that the era of mapping small scale structures has begun. "From here on out, I believe the emphasis will shift to the identification of these structures and what they mean. That is, what do they tell us about how the universe has evolved?