The Day the Stars Ignited

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The first detailed, all-sky picture of the infant universe. The WMAP image reveals 13 billion+ year old temperature fluctuations (shown as color differences) that correspond to the seeds that grew to become the galaxies. Encoded in the patterns are the answers to many age-old questions, such as the age and geometry of the Universe. Credit: NASA/WMAP

A new cosmic portrait — mapping the afterglow of the Big Bang, called the cosmic microwave background — was captured by scientists using NASA’s Wilkinson Microwave Anisotropy Probe (WMAP) during a sweeping 12-month observation of the entire sky.

"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, Greenbelt Md., and the WMAP Principal Investigator. "The data are solid, a real gold mine."

One of the biggest surprises revealed in the data is that 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.

Age of Cosmos

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.

The WMAP team found that the Big Bang and Inflation theories continue to ring true. The contents of the Universe include 4% atoms (ordinary matter), 23% of an unknown type of dark matter, and 73% 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.

"These numbers represent a milestone in how we view our Universe," said Dr. Anne Kinney, NASA director for astronomy and physics. "This is a true turning point for cosmology."

Preceding Patterns of Seeds

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 around us.

Beyond what observers see as the stars and void, the contents of the Universe include a veritable potpourri of exotic types, and just 4% atoms. This is the ordinary matter, the stuff from which stars and everything we see and touch is made. WMAP data reveals that 23% of the Universe is unseen dark matter, a mysterious form of matter intrinsically different from atoms. This matter does not radiate light like ordinary matter, but is detected only indirectly by its gravity. Most of the Universe, 73%, is a mysterious form of energy, dubbed dark energy, that acts as sort of an anti-gravity force and is responsible for accelerating the expansion of the Universe.

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.

Theories about the evolution of the Universe make specific predictions about the extent of these temperature patterns. Like a detective, the WMAP team compared the unique "fingerprint" of patterns imprinted on this ancient light with fingerprints predicted by various cosmic theories and found a match.

Already, astrophysicists have found a new unified understanding of how the universe developed:

  • Universe is 13.7 billion years old with a only a 1% margin error.
  • First stars ignited 200 million years after the Big Bang.
  • Light in WMAP picture from 380,000 years after the Big Bang.
  • Content of the Universe:
    • 4% Atoms, 23% Cold Dark Matter, 73% Dark energy.
    • The data places new constraints on the dark energy. It seems more like a "cosmological constant" than a negative-pressure energy field called "quintessence". But quintessence is not ruled out.
    • Fast moving neutrinos do not play any major role in the evolution of structure in the universe. They would have prevented the early clumping of gas in the universe, delaying the emergence of the first stars, in conflict with the new WMAP data.
  • Expansion rate (Hubble constant) value: Ho= 71 km/sec/Mpc (with a margin of error of about 5%)
  • New evidence for Inflation (in polarized signal)
  • Fate of the Universe: it will expand forever…

What’s Next

WMAP will continue to observe the cosmic microwave background for an additional three years, and its data will reveal new insights into the theory of Inflation and the nature of the dark energy.

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The Universe is much more than what meets the eye. Credit: NASA/WMAP

"This is a beginning of a new stage in our study of the early Universe," said WMAP team member Prof. David N. Spergel of Princeton University, N.J. "We can use this portrait not only to predict the properties of the nearby universe, but can also use it to understand the first moments of the Big Bang."

WMAP is named in honor of David Wilkinson of Princeton University, a world-renown cosmologist and WMAP team member who died in September 2002.

Launched on June 30, 2001, WMAP maintains a distant orbit about the second Lagrange Point, or "L2," a million miles from Earth.

WMAP is the result of a partnership between the NASA Goddard Space Flight Center and Princeton University. Additional Science Team members are located at Brown University, Providence R.I., the University of British Columbia, Vancouver, BC, the University of Chicago, and the University of California, Los Angeles. WMAP is part of the Explorer program, managed by NASA Goddard.