By Dr David Whitehouse
BBC News Online science editor
Scientists have predicted the explosion of a star for the first time.
Amateur astronomers saw the explosion
The star in question is designated Supernova 2003dh and was seen to brighten on 8 April.
The prediction was the consequence of detecting a pulse of energy in the form of gamma rays from the same direction 10 days earlier.
Before this observation, and the prompt given to them by the gamma-ray burst, scientists could not predict the explosion of a supernova to an accuracy of better than a few million years.
Right place, right time
Scientists Arnon Dar and Alvaro de Rujula, from the European Centre for Nuclear Research (Cern) in Switzerland, and the Technion Institute of Technology in Israel, made the prediction about the explosion and watched it happen.
The pair developed a theory to account for the mysterious gamma-ray bursts that come from the depths of the Universe.
For over 30 years, these bursts of high-energy radiation have mystified scientists, who cannot explain their enormous energies.
According to the Cern-Technion team, gamma-ray bursts are linked to supernovae, the cataclysmic explosions of massive stars at the end of their lives.
To test their theory, the researchers needed to wait for a gamma-ray burst that was relatively close, in cosmic terms at least.
On 29 March, a particularly close and powerful gamma-ray burst, designated GRB 030329, was detected.
Looking at their calculations the Cern-Technion team immediately predicted that light from a supernova would first become clearly visible on Earth on 8 April.
And so it did. It has even been detected by advanced amateur astronomers.
This is the first time that scientists have predicted the exact day of observation of a supernova.
Astronomers will now be very interested in why the gamma-ray burst appeared first and the explosion of the star several days later.