Coordinated by the Space and Remote Sensing Sciences Group at Los Alamos, the conference marks the 30th anniversary of the discovery gamma-ray bursts (GRBs) in 1973 by Los Alamos National Laboratory scientists. "This is the beginning of a new era in GRB research," said Marc Kippen, a conference organizer. "This will be the first major conference discussing the fantastic discovery of GRB 030329, which unambiguously establishes that at least some gamma-ray bursts are produced in supernova-like explosions called 'hypernovae.' After decades of wild speculation, theorists finally have a firm footing from which to start."
Nearly 250 physicists and astrophysicists will be on hand for the event to present and debate observations and theories of the relation of the gamma-ray bursts to black holes, neutron stars and other strange astronomical objects. The meeting is at the Santa Fe Hilton, 100 Sandoval Street, and media are welcome to attend. A press conference, with panelists reporting new results that evolve during the conference, will be scheduled for the latter part of the week. Detailed contact information for those wishing to teleconference will be provided in a later media advisory.
Gamma rays, the most energetic form of light known, are emitted from the bursts as brightly as 100 million billion stars. Among the subject areas to be addressed this week will be GRBs as probes of cosmology and the origins of the universe; their relationships to supernovae; automated robot observing systems; ultra high-energy gamma rays, neutrinos, gravity waves and the global properties of the bursts.
"There is a growing consensus that gamma-ray bursts are a rare type of supernova, the hypernova, that involves jets of material that beam the gamma rays, " said Laboratory Fellow Edward Fenimore, lead organizer of the conference. "When Earth is in that beam, the burst is so bright that we can see the gamma-ray bursts from across the entire universe."
This beaming will be a major topic at the conference. Theoreticians will try to explain the beaming, observers will report efforts to measure it and others will exploit the beams to measure the universe when it was very young.
"Another intriguing topic will be the relation between gamma-ray bursts and the so-called X-ray flashes that appear to be related to the same type of explosion," said Kippen. "They could provide the link needed to more clearly understand how the bursts are generated."
These transient bursts of gamma rays from space were discovered in 1973 by Ray Klebesadel and other Los Alamos scientists using data acquired earlier by detectors aboard the Vela treaty-verification satellites. Astrophysicist Stirling Colgate had suggested searching the Vela data for signs of gamma rays emitted during the initial stages of a supernova. Instead of supernovae, they found gamma-ray bursts, which for a few seconds can outshine the rest of the sky at these energies; the origin of the bursts remains a puzzle to astronomers to the present day and forms the basis of energetic debate on the subject.
In 1991, NASA launched the Compton Gamma Ray Observatory (CGRO), carrying four instruments whose data led scientists from the Marshall Space Flight Center to announce that the bursts were coming equally from all directions, which is expected for sources that lie at distances near the edge of the universe. The CGRO re-entered Earth's atmosphere in 2000 at the end of its mission.
A number of other GRB-detection systems have since been launched, among them the HETE-2 satellite, launched in 2000. The HETE program is an international collaboration led by the Center for Space Research at the Massachusetts Institute of Technology for NASA. HETE has 12 networked computers with a sophisticated message architecture that allows the instruments to interact with each other and influence each other's behavior — probably the most complex software ever flown on a satellite of this size. HETE-2 is equipped with instruments sensitive to gamma- and X-radiation. These instruments share a common field of view of ~1.5 steradians, span a detectable energy range of about three decades and are capable of immediate inter-instrument communication.
"Much of the progress that underpins the progress at this conference comes from the HETE satellite," said Fenimore. "What is new is that HETE is routinely locating gamma-ray bursts fast enough and accurately enough that ground-based telescopes can locate the galaxy associated with the gamma-ray bursts before they fade away. This allowed the discovery of a particular burst (GRB030329, occurring on March 3, 2003) that also contained the unmistaken signature of a rare type of supernova."
The Italian Beppo-SAX satellite, which carries sensitive instrumentation from The Netherlands, also is playing an important role, along with the Hubble Space Telescope and powerful radio telescopes in New Mexico, the 10-meter Keck Telescope in Hawaii and the 6-meter telescope at Russia's Special Astrophysical Observatory.
Gamma-ray bursts are unpredictable, high-level emissions of gamma rays originating billions of light years from Earth, ranging in duration from 30 milliseconds to several minutes. These bursts are usually brighter and more energy-intense than the combination of all other sources of gamma rays within the universe added together.
The sources of gamma-ray bursts and their causes are still unknown by astronomers, but it is hoped that new research to be presented this week at the GRB2003 Symposium will bring scientists closer to answering these questions. The conference Web site is at http://grb2003.lanl.gov/ 0nline.
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