http://SaturnianCosmology.Org/ mirrored file For complete access to all the files of this collection see http://SaturnianCosmology.org/search.php ========================================================== SAAO - South African Astronomical Observatory From Archive of 1999 Press Releases The Light of 5 Billion Billion Suns Released: 19 May 1999 *Seizing the Moment* Reacting quickly to an international alert, astronomers at SAAO Sutherland imaged the fading glow of a 'gamma ray burst', the most powerful type of explosion known in the Universe, on May 10. It began at 10:49 SAST when the Burst and Transient Source Experiment (BATSE) on NASA's Compton Gamma Ray Observatory registered an intense burst of gamma rays from a direction less than 10 degrees away from the south celestial pole, in the constellation called the Chameleon. Simultaneously, the Italian-Dutch satellite BeppoSAX also detected the gamma ray burst, and shortly afterward the BeppoSAX Wide-Field Camera located the burst within a patch of sky about 2.0% the diameter of the full moon. Just after dinner that evening, John Menzies of SAAO and Karen Pollard (University of Canterbury, New Zealand) were about to begin the last of 14 nights at the the 1.0-m telescope at SAAO Sutherland, looking for evidence of planets around other stars as part of an international network of astronomers called PLANET. At 17:40, Paul Vreeswijk in Amsterdam phoned with the news that the BeppoSAX had detected telltale gamma rays and X-rays from an explosion in a distant galaxy. The other PLANET sites in Western Australia and Tasmania were clouded out. Phone calls were exchanged through the night as the Sutherland observers obtained images of the region where the X-rays had been detected, then shipped them off electronically to Amsterdam. There Vreeswijk and his collaborators Galama and Rol compared the new pictures to earlier ones of the same part of the sky. The new images showed a star which wasn't on the earlier pictures, and an alert was placed on the international electronic notice board (GCN), giving a precise location for the new object (which was already fading). *Having a Blast With the Big Guns* With an exact position now available, telescopes in Chile started recording the fading explosion a few hours later, and the 8-m Very Large Telescope in Chile was used by a group of Italian astronomers (led by Stefano Corvino of the Brera Observatory in Milan) to measure the polarization of the light from the burst. This is the first time anyone has managed to make such a measurement, and the 1.7% polarization suggests that at least some of the 'afterglow' (the optical radiation, i.e. ordinary light, that ordinary telescopes can see, and which peaks after the gamma rays do) comes from electrons spiralling at very high speeds (a large fraction of the speed of light) around magnetic field lines. The ESO 8-m telescope was also used that night to get spectra of GRB (Gamma Ray Burst) number 990510. From those spectra and the previous measurements of the energy reaching earth, it was possible to calculate the distance and power of the explosion. The answer you get depends on what you assume about the age and expansion of the Universe, but using some fairly plausible numbers for these, the Amsterdam/Huntsville and BeppoSAX follow-up teams found an energy output equal to the energy that the Sun would emit (if it lasted that long) in 1.2 trillion years, about 80 times the likely age of the Universe. The peak power output would be about 5 billion billion times that of the Sun, assuming that the same power was emitted uniformly in all directions. So much for any nearby dinosaurs in that galaxy. But it's by no means certain that dinosaurs would have had time to develop. The explosion took place (depending again on what you assume about the expansion and density of the Universe) somewhere between about 7 to 10 billion years ago, when the Universe was between a quarter and half its present age. To get all this information before the burst faded too much required a precise position as soon as possible. The first southern observatory able to respond to the alert, so that Vreeswijk, Galama and Rol could pinpoint the source, was SAAO Sutherland. *Late Early News from Australia* The earliest images of the burst, however, proved to come from a group of astronomers in Australia who monitor large areas of the southern sky every night. A day after the announcement of the SAAO observations and of the precise position of the burst, the MACHO team in Australia announced measurements of the brightness from pictures beginning five hours earlier than the first sequence at SAAO. *Later News from Sutherland* Astronomers at Sutherland continued to image the fading outburst on the nights of May 12 and 13 (May 11 being cloudy), before it grew so faint that monitoring its brightness was only practical with larger telescopes. *Far and Few* Gamma ray bursts are common -- observing them optically so that their distances can be measured is not. In the 27 months since the detection of the first optical counterpart, only 11 more have been found. The extreme distance and extreme brightness of these mysterious explosions is telling us something we don't understand yet. Every clue is vital, and early measurements crucial. The explosion isn't a simple blast. GRB990510 showed 'two well-separated and multi-peaked pulses' in gamma rays, as though the event somehow stuttered. Such multiple peaks are especially common with large outbursts. *One of the Biggest* The power reaching Earth from the gamma ray burst observed at Sutherland and around the world was in the top 4% of those observed by BATSE, and ranks fourth among those which BeppoSAX has been able to localize. *What Are Gamma Ray Bursts? Are They Really That Big?* BATSE (Burst and Transient Source Experiment) on the orbiting Compton Gamma Ray Observatory (NASA) picks up about one of these brief flashes of high-energy radiation (gamma rays being the most energetic radiation known) per day. Thousands have been detected since they were discovered in the late 1960s. But nobody knew what they were, although BATSE did at least establish that they were so evenly spread over the sky that they must be very distant (and hence very powerful) outbursts of some kind. The breakthrough came two years ago, when for the first time the fading 'afterglow' of one of these explosions was detected in visible light, thanks to the more accurate positions available from the BeppoSAX satellite. Three months later, another optical afterglow was detected -- this time in a faint galaxy whose distance could be measured. A year ago an article in /Nature/ announced the detection of the optical detection of a gamma ray burst in a galaxy more than 12 billion light years away. All theories able to account for the huge energies released in a very short time seem to involve the powerful gravitational fields of black holes. Supergiant stars collapsing to black holes, or black holes coming too close together and merging, allow massive conversion of matter to energy on a short time scale, but even these ideas have trouble accounting for powers as high as observed for the strongest gamma-ray bursts. For this reason, it has been suggested by various theoretical astronomers that the energy from these bursts may not emerge uniformly in all directions, but in 'beams' or 'jets'. It's exactly like the difference between the power required for a torch beam and the power required to light the whole room to the same brightness as the brightest spot lit by the torch. It's for this reason that the measurements of polarization, and the measurements showing that the rate of fading has now increased, were so important. These are the first real evidence to support the idea that the power may be a bit less than 5 billion billion suns -- maybe we're just standing in the beam. *Regular PLANET Hunting* The PLANET collaboration, which involves Dr. John Menzies from the South African Astronomical Observcatory and others at observatories around the world, looks for planets using a technique called 'gravitational microlensing'. This method can pick up planets as small as the Earth, and will give important statistical results about how common planets really are. ESO Press Release 08/09 : Southern Fireworks above ESO Telescopes - New Observations of Mysterious Gamma-Ray Burst. Contacts:* John Menzies and David Laney