We're not as ancient as we thought

THE UNIVERSE is 12 billion years old - about 1 billion years younger than previously thought. Scientists are hailing the latest calculation as one of the most important breakthroughs in cosmology for 70 years, when astronomers first realised stars and galaxies were flying apart in an expanding universe.

Yesterday an international team of astronomers said the Hubble space telescope had calculated the Universe's age to within 10 per cent of its true value - the most accurate estimate yet. Nasa said the age was estimated from Hubble's measurements of cosmic distances between a special class of pulsating star called Cepheid variables. "Before Hubble, astronomers could not decide if the Universe was 10 billion or 20 billion years old," said Wendy Freedman, an astronomer at Carnegie Observatories, Pasadena, California, and leader of the team.

Scientists estimate the Universe's age by calculating its rate of expansion with the help of measurements of the distances between far-off galaxies. A key component in the calculations is the Hubble constant, a term describing the relationship between the speed with which galaxies are moving apart and their distances. The bigger the constant, the younger the Universe.

The astronomers investigated 18 galaxies out to a distance of 65 million light-years to locate nearly 800 Cepheid variable stars.

These are the "standard candles" whose light intensity is known and can be used to estimate distances accurately.

Hubble data on Cepheid variables concluded that galaxies appear to be moving 160,000mph faster for every 3.3 light-years they are farther from Earth.

"Combining the Hubble constant measurements with estimates for the density of the Universe, the team determined that the Universe is approximately 12 billion years old - similar to the oldest stars," said a Nasa spokesman.