LONDON (Reuters) - First scientists thought it was slowing down, then they discovered it was speeding up. Now a team of international astronomers say the universe is expanding even faster than they thought.
Their calculations, reported in the science journal Nature on Wednesday, are based on the brightness of giant pulsating stars called Cepheids, which are used by astronomers to determine distance to other galaxies.
The fact that the Cepheids appear to be fainter than previously thought means they are also closer to the earth, Professor Stephen Zepf, of Yale University, said in a statement.
``The reason this is significant is that since Cepheids are used to calibrate the expansion of the universe, if they are fainter, then the universe is expanding slightly faster. If the universe is expanding slightly faster, then it might be a little younger than we thought.''
Cepheids have been used as standard measurements to estimate cosmic distances since 1929. They pulsate in a particular way that depends on their brightness, which viewed from the Earth indicates how far away they are from us.
``Nearly all galaxies are moving away from us. The question is whether this will keep going on forever or whether eventually the universe will have enough density to collapse back on itself,'' Zepf added.
Using the Hubble Space Telescope, Zepf and scientists from the NASA Ames Research Center in California, the University of California in Berkeley and the California Institute of Technology discovered that the Cepheid stars may be about 15 percent fainter than previously thought.
``This is analogous to finding out that the light bulb you thought was 60 watts is really only 50 watts, therefore the lamp is actually closer than you originally estimated,'' Zepf said.
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