‘Telescope’ Uncovers Space Secrets From Antarctic Ice

A “telescope” that lies deep inside the ice sheet covering Antarctica has shown it can detect elusive particles called high-energy neutrinos as they travel from space and pass all the way through the Earth.

The instrument, called AMANDA, may help change fundamental theories about the tiny world of particle physics while stretching the view of astronomers to the edge of the universe.

Understanding neutrinos better may offer clues about things like black holes or the composition of so-called “dark matter” that fills much of the universe.

The Antarctic Muon and Neutrino Detector Array, designed by physicist Francis Halzen at the University of Wisconsin-Madison, lies nearly a mile below the South Pole.

It consists of hundreds of glass bulbs the size of bowling balls embedded in crystal-clear ice waiting for telltale flashes of ghostly blue light. The faint flashes mark the passage of neutrinos when they spawn other particles, called muons.

“This is a very cool tool,” said Janet Conrad, a Columbia University physicist who conducts research at the Fermi National Accelerator Laboratory in Batavia, Ill.

“Every time we look at the sky in a new way, we always see something we didn’t expect,” Conrad said.

In a recent edition of the journal Nature, Halzen and a large team of physicists and astronomers report the AMANDA array successfully detected neutrinos that passed all the way through the Earth, the first important step to detecting even higher energy neutrinos traveling from much greater distances.

“This is an idea that goes back to the 1950s,” Halzen said. “The problem was that nobody could do this, until now.”

High-energy neutrinos interact so weakly with the matter that makes up the Earth and everything on it that very sensitive--meaning very large--detectors are needed to study them.

Other neutrino detectors exist, including one in Russia, but they cannot easily be enlarged to the size needed for the extreme sensitivity required to capture particles zooming through the planet from the edge of the universe, Halzen said.

Drilling the ice and assembly of the $7-million AMANDA array began in 1990, and it first started taking measurements in 1999.

Plans call for an expanded version called IceCube that will cover a square kilometer--about two-fifths of a square mile--under the South Pole, making it the largest detector ever built.

But first, it was important for researchers to show if the concept works, and their report in Nature confirms it does, said John Bahcall of Princeton.

“I think that a neutrino telescope with this sensitivity will show us something we didn’t know,” Bahcall said. “And that’s been true of every major telescope development since Galileo.”