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The Honolulu Advertiser
Posted on: Tuesday, October 11, 2005

Mauna Kea teams help solve cosmic mystery

By Kevin Dayton
Advertiser Big Island Bureau

HILO, Hawai'i For 35 years astronomers have puzzled over the source of short gamma ray bursts in space, jolts of energy that last less than a few seconds. Scientists couldn't identify the sources of the electromagnetic radiation.

Astronomers using equipment on Mauna Kea helped to crack that puzzle by gathering data on a half-second July 9 gamma-ray burst to calculate the distance to the source some 1.3 billion light years away, at the edge of another galaxy.

Astronomers theorize the source was either a collision of two dying stars, or a black hole ripping apart and consuming a neutron star.

"There are tremendous energies involved, and so the only sources that we really know of out there in the universe that can do this are black holes and neutron stars," said Paul Price of the University of Hawai'i's Institute for Astronomy.

The short gamma-ray bursts were first discovered by U.S. military satellites designed to monitor Russian nuclear tests in the late 1960s. Astronomers couldn't be certain whether the bursts were coming from somewhere close to home in the solar system, or from distant galaxies.

NASA's High-Energy Transient Explorer satellite detected the July 9 burst, and notified Price and Kathy Roth of the Frederick C. Gillett Gemini Telescope on Mauna Kea along with other astronomers.

NASA scientists then aimed the Chandra X-ray Observatory, which is on another satellite, at the source of the energy. Chandra recorded an "afterglow" of X-ray radiation from the same source.

The Gemini telescope on Mauna Kea was then used to calculate the distance to the galaxy where the explosion occurred, and scientists were able to use that information to calculate the strength of the blast.

Those calculations showed the amount of energy involved was so enormous that it could come from only a few known sources: Either two neutron stars had been circling each other and finally collided, or a neutron star paired with a black hole was finally consumed by the black hole.

A supernova explosion was another possibility, but scientists ruled that out because there was no other telltale sign of an exploding star.

In papers published earlier this month in the science journal "Nature," Price, Roth and collaborators at other observatories conclude the initial quick blast of gamma-ray radiation may be the black hole swallowing most of the neutron star, which is a rare type of dead star so dense that each cubic inch weighs more than a trillion tons.

The bursts of X-ray light after the gamma-ray burst may be remaining bits of the neutron star material falling into the black hole.

Price and the Mauna Kea telescopes also had a hand in gathering information on another gamma-ray burst in September that originated 12.8 billion light years away, making it the most distant cosmic explosion ever recorded.

Reach Kevin Dayton at kdayton@honoluluadvertiser.com.