Windows on a violent universe Scientist focuses on neutrino research

October 29, 1991|By Douglas Birch

They are ghostly pinpricks of matter so elusive they can pass easily through miles of rock and metal.

But Demosthenes Kazanas, a NASA astrophysicist, thinks these faint specks could become the foundation of a whole new branch of astronomy.

They're high-energy neutrinos. And Dr. Kazanas, a 41-year-old Severna Park resident, wrote in a recent issue of the scientific journal Nature that telescopes designed to detect the decay products from these particles could give scientists CAT scan-style images of the Earth's core and provide a clearer picture of the star-swallowing black holes at the center of some galaxies.

Neutrinos, created when high-energy protons collide with other matter, are subatomic particles that carry no electric charge, travel at close to the speed of light and have a mass too close to zero to be measured.

Low-energy neutrinos coming from the sun have been detected for about 20 years. But astronomers hope that new instruments being built or planned will detect neutrinos about a million times more energetic that may be sprinkling in from distant galaxies.

Most telescopes measure waves in the electromagnetic spectrum, from optical light to X-rays to gamma rays.

Neutrino telescopes would offer a new window on the often-violent processes that lead to the creation and destruction of stellar objects.

One of those instruments is the DUMAND, an array of sensitive light detectors now being installed three miles under the surface of the Pacific Ocean off the island of Hawaii.

The instrument, designed to detect neutrinos that have passed through the Earth's core, detects high-energy neutrinos indirectly by using special tubes that spot tiny flashes of light. Those flashes are muons, short-lived particles created when neutrinos hit rock or water near the detectors.

Ocean-floor drilling began on DUMAND -- Deep Underwater Muon and Neutrino Detector -- in July. It is expected to cost the Department of Energy $10 million and open for business in late 1993 or 1994.

No one is sure what DUMAND will find. "It's a real risky project," Dr. Kazanas said. "Someone has to go three miles deep in the ocean and put the detectors there. It's never been done before."

There is a chance the instrument won't be sensitive enough to detectthe high-energy particles, he said. "And if these [galactic] sources don't make neutrinos, then it won't work anyway."

But, he said, "even if we see nothing it will still tell us some- thing."

Dr. Kazanas, who works at the Goddard Space Flight Center in Greenbelt, said the telescope could help scientists describe the mechanism that generates huge amounts of energy bursting from the centers of some galaxies.

Scientists have discussed about 10 other neutrino telescopes. One would sink light-sensitive tubes 3,000 feet into the ice of Antarc- tica.

In 1987, scientists inadvertently discovered that supernovas -- in which the core of a star collapses into a neutron star or black hole -- produce bursts of neutrinos. A nearby supernova, the first in at least a century, triggered low-energy neutrino detectors in mines in Japan and the United States. That helped spur interest in a neutrino telescope.

Dr. Kazanas said a sensitive "telescope" might be able to take a picture of the Earth's interior.

The detector would work like a CAT scan, measuring the intensity of a stream of neutrinos as they barrel through the planet. Dense rock would probably absorb more of the particles; lighter material would let more neutrinos pass.

"You can get a feeling of what the density of the core of the Earth is," he said.

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