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Scientists solve 35-year-old mystery of cosmic explosions UNIVERSITY OF CALIFORNIA-BERKELEY NEWS RELEASE Posted: October 5, 2005 An international team of scientists using data from a small NASA spacecraft has put into place a large piece of the astronomical puzzle of short-duration gamma-ray bursts.
The team, which includes Kevin Hurley, senior space fellow at the University of California, Berkeley's Space Sciences Laboratory, will announce its results in the Oct. 6 issue of the journal Nature. "This is the first secure measurement that links the short bursts to the compact object collision theory," said Garrett Jernigan, a research physicist at the laboratory. One of the nagging mysteries of cosmic gamma-ray bursts, the most luminous explosions in the universe, is whether all are produced the same way. "These bursts come in a bewildering array of shapes and varieties, and when you're shopping for a theory to explain them, one size may not fit all," Hurley said. The breakthrough burst came on July 9 from the constellation of Grus (the crane) in the southern sky, and lasted only one-tenth of a second. The burst was captured by HETE-2, a spacecraft launched in 2000 by an international collaboration involving the United States, Japan, France and other partners. "That was the clue we were waiting for," said Jernigan. "Bursts seem to come mainly in two varieties - the long ones, which last about 20 seconds, and the short ones, which last a few tenths of a second. It's the short ones that have still been puzzling us." Evidence has mounted over the years that the longer bursts are caused by the collapse of massive stars in distant galaxies. These stars, which contain about 30 times the matter that our sun does, run out of nuclear fuel and collapse into black holes, emitting prodigious amounts of energy in gamma-rays, which are a very energetic version of X-rays. For the short bursts, though, there was no evidence that this was the case. On the contrary, there were many theories that these bursts are produced by the collision of two small, compact objects - either two neutron stars, or one neutron star and a small black hole. In either case, a larger black hole is formed as the result of a collision. The HETE-2 spacecraft pinpointed the source of the short burst on July 9 and triggered a series of observations by NASA's Chandra X-Ray Observatory and Hubble Space Telescope, as well as by a host of ground-based observatories. What they found, for the first time, was a faint, short-lived optical afterglow, which represents the embers of the explosion which produced the burst. This, in turn, allowed astronomers to identify the galaxy in which the burst had occurred, and to measure its distance. To their surprise, it was relatively nearby, by astronomical standards. "This burst took place only one billion light years from Earth, instead of the usual 10 billion light-years for the long bursts," said Nat Butler, a Townes Fellow at UC Berkeley and part of the HETE team. "When you do the math, it turns out that this was about a thousand times less energetic than a typical long burst." Another clue came from the position of the burst within the galaxy. It was on the outskirts, where double neutron star systems are expected to be. The details of the Hubble and Chandra observations, which clinch the case, are being published in a companion Nature paper by Derek Fox of Pennsylvania State University and his colleagues. Neutron stars are the remnants of normal stars after they have burned out. They measure about 10 miles in diameter, but contain the same amount of mass as our sun. They can exist in binary systems, where two neutron stars orbit each other, or where one neutron star orbits a black hole. Eventually, though, these systems must decay and the compact stars must collide, producing gravitational waves predicted by Albert Einstein's general theory of relativity. These waves have never been detected directly, and that is the goal of the Laser Interferometer Gravitational Wave Observatory (LIGO), which has just begun operation. "It's possible now that the first gravitational wave source that LIGO observes will also be a gamma-ray burst source," said Hurley. "Now that would be a spectacular discovery." |
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NASA astronauts Bill McArthur and John Phillips chat with Associated Press space reporter Marcia Dunn about life aboard the International Space Station in this live space-to-Earth interview from the Destiny laboratory module on October 5.
In preparation for the West Coast launch of Boeing's next-generation Delta 4 rocket, the two-stage vehicle is rolled out of its horizontal hangar and driven to the Space Launch Complex-6 pad for erection. The nose cone for the NRO payload is then brought to the pad.
Boeing's Delta 4 rocket pad at Vandenberg Air Force Base was renovated in recent years, transforming Space Launch Complex-6 from the West Coast space shuttle launch site into a facility for the next-generation unmanned booster. This collection of footage shows the 1985 launch pad test using NASA's orbiter Enterprise.
The Expedition 11 and Expedition 12 crews, along with space tourist Greg Olsen, hold a live news conference with American and Russian reporters on October 4. (26min 36sec file)
A Russian Soyuz spacecraft safely launched from Baikonur Cosmodrome Friday night with the International Space Station's twelfth resident crew and a paying tourist aboard.
The seven astronauts of space shuttle Discovery's return to flight mission recently gathered for a public celebration of their mission. They narrated an entertaining movie of highlights and personal footage taken during the mission.
The Boeing Delta 2 rocket roars off Cape Canaveral's launch pad 17A carrying the first modernized Global Positioning System satellite for the U.S. Air Force.
NASA unveils the agency's blueprint for building the future spacecraft and launch vehicles needed for mankind's return to the lunar surface in the next decade.
Astronomers announce the detection by NASA's Swift satellite of the most distant explosion yet, a gamma-ray burst from the edge of the visible universe, during this media teleconference held Monday, September 12. (54min 01sec file)
The Mars Exploration Rover Spirit has reached the summit of Husband Hill, returning a spectacular panorama from the hilltop in the vast Gusev Crater. Scientists held a news conference Sept. 1 to reveal the panorama and give an update on the twin rover mission.
To gain a new perspective on space shuttle Discovery's ascent and gather additional imagery for the return to flight mission, NASA dispatched a pair of high-flying WB-57 aircraft equipped with sharp video cameras in their noses.
When space shuttle Discovery launched its two solid-fuel booster rockets were equipped with video cameras, providing dazzling footage of separation from the external fuel tank, their free fall and splashdown in the sea.
