Partnership produces sharp 'baby pictures' of the universe

By Steven Schultz

Princeton NJ -- NASA announced Feb. 11 that a satellite built in collaboration with Princeton scientists has captured a high-resolution snapshot of the universe in its infancy and produced dramatic insights into astronomy and physics.

The Wilkinson Microwave Anisotropy Probe, a satellite designed and built in a partnership between Princeton and NASA, produced a map of the afterglow of the big bang with far greater resolution than ever before. The top image shows a map that resulted from NASA's COBE satellite, which discovered faint ripples in the radiation in 1992. The bottom image shows the results from the Wilkinson satellite, which has 35 times greater resolution and 45 times greater sensitivity than COBE.
Answers to longstanding questions about the age, composition and evolution of the universe snapped into sharper focus with the arrival of the data, which came from a yearlong observation of remnants of light from the big bang itself.

"We have a map of the earliest light of the universe that is complete, and it is stunning to look at," said Princeton physicist Lyman Page.

The space agency also announced that it has named the satellite that collected the data in honor of Princeton physicist David Wilkinson, who was a founding member of the project team and who died in September 2002. The Wilkinson Microwave Anisotropy Probe measures slight ripples -- or anisotropies -- in the big-bang afterglow that suffuses the universe.

Among the most surprising results is the discovery that the first stars formed just 200 million years after the big bang, sooner than previously thought. Scientists had thought that the first stars formed when the universe was 800 million years old.

Other implications arising from the data include:

• A dramatically sharper measure of the age of the universe -- 13.7 billion years, plus or minus .2 billion years. That margin of error is no more than the length of time dinosaurs roamed the earth; previous estimates had uncertainties many times larger.

• A refined estimate of how much matter exists in the universe and strong evidence that the universe is dominated by some form of "dark energy" that is tearing it apart. According to the project scientists, the universe consists of 4 percent ordinary matter, 23 percent dark matter of unknown form and 73 percent dark energy. Some previous studies had suggested more matter and less dark energy.

• A revised and more complex picture of the first microsecond of the big bang, when the universe appears to have undergone a period of hyperfast expansion called inflation.

"These numbers represent a milestone in how we view our universe," Anne Kinney, NASA director for astronomy and physics, said in the space agency's news release. "This is a true turning point for cosmology."

"The really remarkable thing is that it all fits," said David Spergel, a Princeton astrophysicist and a participant in the project. The data tie together many previous observations from the Hubble Space Telescope and other sources, essentially completing the basic picture of how the universe began, he said.

"We have now answered many of the questions that have driven the field for the past few decades," said Spergel. "How old is the universe? How much matter is in it? How fast is it expanding? And now we're getting to address a new set of questions: How did the first stars form? What are the properties of the dark energy that makes up most of the energy in the universe?"

The light measured by the satellite is known as the cosmic microwave background. It is energy that was trapped in the hot gasses of the early universe and was suddenly released at a point 380,000 years after the big bang. This light, which has been spreading through the universe ever since, contains extremely subtle fluctuations that reveal the physical properties of the cloud from which it emerged.

Today this radiation, which began at nearly 4,000 degrees Celsius, imparts to the universe a background temperature of just 2.73 degrees above absolute zero. The Wilkinson satellite measured fluctuations in that temperature of just millionths of a degree, as well as other equally subtle irregularities.

The results are a first pass at analyzing data that are expected to emerge more fully over the next three years. The satellite, launched in June 2001, occupies a unique point in space 1 million miles from Earth where it orbits the sun and maintains a straight line between the sun, Earth and satellite. This vantage point, four times farther away than the moon, offers an exceptionally quiet place to observe the cosmos.

The satellite mission is a partnership between NASA's Goddard Space Flight Center in Greenbelt, Md., and Princeton, with additional collaborators at Brown University, the University of British Columbia, the University of Chicago and the University of California-Los Angeles. NASA scientist Charles Bennett is the project leader.

"The whole group is just a fantastic team," said Page, who attributed the mission's success to the sustained and close-knit collaboration between the scientists and the support of many technical specialists at NASA and Princeton.

David Wilkinson, a founding member of the project team, died in September 2002
For Wilkinson, the project was the last in a series of increasingly refined measurements of the cosmic microwave background that he had been making for more than 30 years. NASA's decision to name the satellite after him could not be more fitting, said Page. "It's the perfect tribute to his leadership of the field for so many years."

Other team members at Princeton include senior research staff scientist Norman Jarosik, postdoctoral researchers Christopher Barnes, Michael Nolta, Eiichiro Komatsu and Licia Verde, and graduate student Hiranya Peiris. Technicians in the University's physics machine shop built several key components of the detectors.

For those involved, the announcement of results is a long-awaited moment. "It was very challenging, but it also is fun to know that things that I worked on and screws that I tightened are now a million miles away and are working," said Jarosik, who designed the main parts of the detectors.

"I just love the kind of things you can tell by looking at the sky," said Jarosik. "This light is up there; it's there for anyone who can build a good enough instrument to look at it."

The Wilkinson satellite is expected to collect data for another three years and could function for twice that long. In the meantime, scientists at Princeton already are planning new ground-based observations that will add further clarity to the cosmic microwave background picture. For more information, visit this Web site: topstory/2003/ 0206mapresults.html

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