By Dr David Whitehouse
BBC News Online science editor
The Universe could be a billion years older than was thought, according to Italian and German scientists.
Some stars may live longer than was thought
Measurements made in an underground laboratory suggest an atomic reaction that produces energy inside stars is slower than was believed.
It means that estimates of stellar lifetimes are too short. A readjustment gives the Universe an age of 14.7 instead of 13.7 billion years.
The results are to be published in the journal Physics Review Letters.
The new result comes from Luna - the Laboratory for Underground Nuclear Astrophysics - situated underneath Gran Sasso mountain in Italy.
In Luna, scientists from the Italian Institute of Nuclear Physics and the University of Bochum in Germany are reproducing one of the energy-producing nuclear reactions that take place inside the Sun.
Simulating a piece of the Sun
"In an ordinary laboratory on the surface, the effects of the reaction studied by Luna would be hidden by similar, but much more abundant, effects. Because our laboratory is under 1,400m of rock, we have an isolated base to make these delicate measurements," says Luna co-ordinator Dr Carlo Broggini.
The cycle they are studying - the carbon-nitrogen-oxygen cycle - only supplies a tiny fraction of our Sun's energy. It is far more important in larger stars.
The result obtained suggests that the carbon-nitrogen-oxygen cycle takes place at half the rate as was believed.
The implications are that massive stars live longer than was first thought, a factor that affects estimates of the age of the Universe based on the ages of the oldest stars.