UH astronomers track invisible pyrotechnics
Mauna Kea facilities help locate the source of a gamma ray burst
Using space telescopes and the Gemini telescope on Mauna Kea, astronomers scored two firsts in July: They pinpointed the source galaxy of a short gamma ray burst, and they calculated the distance of the burst from Earth.
"We've finally tracked down a short burst to a small galaxy a long way from our own," said University of Hawaii astronomer Paul Price.
The cause of the July 9 burst is believed to be the collision of two dead stars, according to a UH Institute for Astronomy statement.
The findings by Hawaii astronomers Price and Kathy Roth of the Gemini North observatory, working with other astronomers around the world, were published yesterday in the journal Science.
Gamma rays are an extremely high-energy form of radiation, more energetic than X-rays.
If a gamma burst happened even somewhat close to Earth, it would destroy the protective ozone layer, electrify the atmosphere and cause widespread destruction of life, Price said.
Such a burst is expect 300 million years from now from a pair of neutron stars just 3,000 light-years from Earth, Price said.
Price and Gemini astronomer Roth calculated the distance of the July 9 gamma burst as 1.3 billion light-years, meaning it was much too far away to affect Earth.
Astronomers have known about short gamma bursts, lasting no more than about two seconds, for about 35 years. They were first discovered by U.S. military satellites designed to monitor Russian nuclear tests.
But those satellites had low resolution, meaning they could not tell exactly where the flashes were coming from or how far away they were.
The short bursts from neutron stars are different from another type of gamma flash, called long bursts, which last a few minutes and are believed to be caused by supernovas, Price said.
The July 9 event was first detected by NASA's High Energy Transient Explorer satellite, then observed with the Chandra X-ray satellite and finally by the Gemini Telescope on Mauna Kea.
The original burst lasted just a half second, a Chandra statement said. But the event created a shock wave in the highly rarefied matter of space, with the wave still visible days later, Price said.
Astronomers believe the event started with a neutron star falling into a black hole or possibly two neutron stars spinning around each other until they collided and both fell into a black hole.
Neutron stars are dense, dead stars in which matter weighs more than a trillion tons per cubic inch, the UH statement said. But matter in a black hole has a density that can be considered infinite, Price said.
Although anything coming too close is sucked into a black hole, a blast of material is also thrown off, hitting other matter, creating gamma and X-rays, Price said.