Gauging Age of Universe Becomes More Precise

The universe is 13.73 billion years old, give or take 120 million years, astronomers said last week. That age, based on precision measurements of the oldest light in the universe, agrees with results announced in 2006. Two additional years of data from a NASA satellite known as the Wilkinson Microwave Anisotropy Probe have narrowed the uncertainty by tens of millions of years. “Everything is tightening up and giving us better and better precision all the time,” said Charles L. Bennett, a professor of physics and astronomy at Johns Hopkins University and the leader of the group analyzing the data. “It’s actually significantly better than previous results. There is all kinds of richness in the data.” About 380,000 years after the Big Bang, the universe cooled enough for protons and electrons to combine into hydrogen atoms. That released a burst of light, which over the billions of years since has cooled to a bath of microwaves pervading the cosmos. Yet there are slight variations in the background, which the NASA satellite has been measuring since 2001. Those variations have given evidence supporting an idea known as cosmic inflation, a rapid expansion of the universe in the first trillionth of a trillionth of a second of its existence. The new set of data is precise enough to differentiate between various proposed models of inflation. “Some of them are now completely ruled out, some of them are hanging at the edge and some of them are perfectly fine,” Dr. Bennett said. “We are sorting between these things.” Astronomers can also now see strong evidence for the universe being awash in almost massless subatomic particles known as neutrinos. This sea of primordial neutrinos created in the Big Bang was expected. “The new result is that it’s not consistent with zero anymore,” said Edward L. Wright, a professor of physics and astronomy at the University of California, Los Angeles, and another member of the team. As more years of data are gathered, Dr. Bennett said, astronomers may even be able to deduce new unusual types of neutrinos that have so far not been detected in particle accelerators. The new data also refine findings that the earliest stars switched on 400 million years after the Big Bang. The starlight started breaking up interstellar hydrogen atoms back into charged protons and electrons — creating a fog that deflected the cosmic microwaves — but took half a billion years to break apart all of the atoms.