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.