NASA reveals end of universe’s dark ages

UCLA astronomer played key role in data analysis

The universe had a period of “Dark Ages,” starting approximately half-a-million years after the Big Bang, and NASA’s Wilkinson Microwave Anisotropy Probe (WMAP) has revealed the end of the Dark Ages.

“We detected the end of the Dark Ages about 200 million years after the Big Bang,” said Edward L. Wright, professor of astronomy at UCLA, who helped develop key data analysis techniques for WMAP. “There were enough bright stars and quasars at that time to fill the universe with ultraviolet light and a haze of cosmic electrons. This is nearly 700 million years earlier than any of these objects has been seen before. WMAP measurements have enabled us to detect the era when the first stars formed.”

NASA’s WMAP mission observes the universe as it was 380,000 years after the Big Bang, and is making a detailed investigation of the sky’s cosmic microwave background — the radiant heat left over from the Big Bang — to help us understand the structure of the universe.

NASA has announced that the satellite has been renamed to honor WMAP team member David Wilkinson of Princeton, who died in September 2002.

“The properties of the radiation contain a wealth of information about physical conditions in the early universe,” said Wright, whose areas of expertise include cosmology and infrared astronomy. The cosmic microwave background is to cosmology what DNA is to biology, Wright and his WMAP colleagues noted.

WMAP has provided insights into the amount of mysterious dark matter in the universe; many scientists had believed dark matter makes up 90 percent or more of the universe. The figure is much lower, WMAP measurements reveal.

“About 23 percent of the universe is dark matter,” Wright said. “About four percent is ordinary matter, such as hydrogen, helium, oxygen and carbon. The remaining 73 percent of the universe is dark energy, which Albert Einstein postulated (in 1917) as a cosmological constant.”

Einstein later believed that to be a serious blunder, but it turns out he was right.

“Five years ago, many astronomers believed 90 percent of the universe was dark matter and 10 percent was ordinary matter,” Wright said.

WMAP reveals the universe is 13.7 billion years old, with an uncertainty of only 200 million years.

What is the ultimate fate of the universe? “Measurements from the mission tell us that the ultimate fate of the universe will be to expand forever, rather than collapse,” Wright said.

“In 10 to 20 billion years, there will be many fewer galaxies visible from Earth,” he said. “In 100 billion years, the sky will be pretty empty as the accelerating expansion caused by the dark energy moves galaxies to great distances from the Earth. Nearby galaxies will remain, but the Milky Way will actually collide with the Andromeda galaxy, now two million light-years away, and merge with it in approximately five or six billion years.”

The new WMAP data also strengthen the Big Bang theory, and strongly support experiments showing that the shape of the universe is flat.

WMAP launched on June 30, 2001, and reached its observing station, more than 900,000 miles from Earth, some three months later.

At a press conference Feb. 11 at NASA headquarters in Washington, D.C., the principal investigator for WMAP, Charles L. Bennett of Goddard Space Flight Center, and WMAP colleagues discussed the insights WMAP is providing. They also presented new images of the whole sky showing the details of the cosmic background.

The farthest objects scientists have seen before WMAP date back from when the universe was about seven-and-a-half times smaller than it is today.

“With WMAP we now see evidence of stars that existed when the universe was 20 times smaller than it is today,” Wright said.

He said WMAP has already been extremely successful.

“I’m very pleased with how WMAP has worked, and how well everything has gone,” Wright said.

WMAP will observe for another three years. The mission brings together expertise from the Goddard Space Flight Center, Princeton University, UCLA, the University of Chicago, the University of British Columbia and Brown University.

Information about the WMAP mission is available on the Web at map.gsfc.nasa.gov.