Universe's Age: 12 Billion Years

0 Comments | Insight on the News, July 5, 1999 | by Ruth Larson

Astronomers using the Hubble space telescope say the universe is about 12 billion years old, far younger than some earlier estimates that placed its creation as long as 20 billion years ago.

"Before Hubble, astronomers could not decide if the universe was 10 billion or 20 billion years old," says Carnegie Observatories astronomer Wendy Freedman, who headed the team that measured the rate of expansion. "The size scale of the universe had a range so vast that it didn't allow astronomers to confront with any certainty many of the most basic questions about the origin and eventual fate of the cosmos."

Freedman and her team of 27 astronomers used the Hubble to measure precisely the distance to objects called Cepheids, young stars found in the "arms" of spiral galaxies. During its eight years of work, the team found almost 800 of these pulsating stars in 18 galaxies. Cepheids provide a reliable yardstick for measuring intergalactic distances.

To confirm its results, the team used four different methods of estimating the Hubble constant. All four methods have given "a remarkably consistent result," says Freedman.