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Cosmic Microwave Background – an Image of the Infant Universe
Scientists using NASA's Wilkinson Microwave Anisotropy Probe
(WMAP), during a sweeping 12-month observation of the entire sky,
captured the new cosmic portrait—the afterglow of the
big bang, called the cosmic microwave background, or CMB. The light we see today, as the cosmic microwave background, has
traveled over 13 billion years to reach us. Within this light are
infinitesimal patterns that mark the seeds of what later grew
into clusters of galaxies and the vast structure we see all
"We've captured the infant universe in sharp focus, and from this portrait we can now describe the universe with unprecedented accuracy," said Dr. Charles L. Bennett of the Goddard Space Flight Center (GSFC), Greenbelt Md., and the WMAP Principal Investigator. "The data are solid, a real gold mine," he said.
One of the biggest surprises revealed in the data is the first generation of stars to shine in the universe first ignited only 200 million years after the big bang, much earlier than many scientists had expected. In addition, the new portrait precisely pegs the age of the universe at 13.7 billion years old, with a remarkably small one percent margin of error.
Analyzing the data, the WMAP team found that the contents of the universe include 4 percent atoms (ordinary matter), 23 percent of an unknown type of dark matter, and 73 percent of a mysterious dark energy. The new measurements even shed light on the nature of the dark energy, which acts as a sort of an anti-gravity. The data also show that the universe is currently expanding at the rate of 71 km/sec/Mpc (accurate to 5 percent), underwent episodes of rapid expansion called inflation, and will expand forever. Astronomers will likely research the foundations and implications of these results for years to come.
Patterns in the big bang afterglow were frozen in place only 380,000 years after the big bang, a number nailed down by this latest observation. These patterns are tiny temperature differences within this extraordinarily evenly dispersed microwave light bathing the universe, which now averages a frigid 2.73 degrees above absolute zero temperature. WMAP resolves slight temperature fluctuations, which vary by only millionths of a degree.
Launched on June 30, 2001, WMAP maintains a distant orbit about the second Lagrange Point, or "L2," a million miles from Earth.
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