The biggest explosion in space since the Big Bang has been detected and measured by scientists who have no idea what caused it. The explosion, originally spotted as an incoming burst of gamma ray radiation, was detected on December 14th by the Italian/Dutch BeppoSAX satellite and NASA's Compton Gamma Ray Observatory satellite.
"The energy released by this burst in its first few seconds staggers the imagination," said Prof Shrinivas Kulkarni of the California Institute of Technology, who with Prof George Djorgovski, published a report on the event in the science journal, Nature.
"For about one or two seconds, this burst was as luminous as all the rest of the entire universe," Prof Djorgovski said. The burst was estimated to have lasted for about 50 seconds, releasing about as much energy as our own Milky Way galaxy would over a couple of centuries.
The satellite data told the researchers where in the night sky to look for visual remnants of the explosion and the word went out to point telescopes in this direction. As visible light from the burst afterglow faded, the world's largest telescope, the 10-meter Keck II in Hawaii, found a weak light source about 12 billion light years away.
The Hubble space telescope later confirmed the source as a faint galaxy, about as faint as an ordinary 100 watt light bulb would be seen from a distance of a million miles. Scientists measured the redshift of the light to calculate the distance and then estimated the energy released to enable something so far away to be picked out by a telescope.
Scientists were dumbfounded by the results. They described as unprecedented the discovery of such a large energy release over such a brief period of time, other than the Big Bang itself. Few models other than those proposing enormous rotating black holes could explain such an event, said Prof Kulkarni. "This is such an extreme phenomenon that it is possible we are dealing with something completely unanticipated and even more exotic."
Scientists have been scanning the skies for some years looking for what are known as gamma-ray bursts and the two satellites were designed specifically for this. The bursts were detected by accident during the Cold War by satellites watching for nuclear explosions on earth. But none seen so far was anything like as powerful as this one.
There is a world network of scientists organised to respond to bursts, including a team at University College, Dublin. They wait for word from the BeppoSAX or Compton satellites of a gamma-ray burst and then hurry to point telescopes, hoping to catch any light coming from the event. The data are then shared around the network as the research teams wait for the next opportunity to catch a burst in action.
