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A neutrino telescope in the Antarctic ice
a transcript to accompany the Real Media animation

The universe is full of mysteries. Only a part of its enigmatic variety can be glimpsed with the human eye. Only by using modern detection systems can scientists decode the invisible messages from the cosmos.

For some time there has been a new window into the universe that permits us to see space under a totally different light: neutrino astronomy. Physicists from the research center DESY, together with American and European colleagues, operate the new neutrino telescope. It consists of 670 light sensors, which are melted into the ice of the South Pole. Its name: AMANDA!

AMANDA is an array of devices for detecting muons and neutrinos. A constant rain of cosmic rays flows though the universe: light, nuclei, neutrinos, and muons.

Neutrinos are extremely small elementary particles that have one very particular feature: a strong antipathy for interaction with other matter. Light and nuclei are often swallowed by cosmic dust cloudsl neutrinos travel through space almost unaffected.

Billions of neutrinos reach the earth every second. As messengers from their place of origin, they carry information from very distant galaxies, supernovae explosions, and undiscovered objects.

Neutrinos are unaffected as they penetrate the Earth, and as they travel through the glowing center of the planet.
Are they completely unaffected? Well, not quite.

A microscopic view shows how the travel of these ghost particles can sometimes be stopped: by an extremely rare collision with the nucleus of an atom.

Here is a neutrino colliding with a water molecule of the arctic ice. This collision breaks the nucleus apart, and the neutrino converts to a muon, which is basically a heavy electron.

From the side, you can see another view of the muon's birth. This particular muon will be picked up by the detectors. Muons are able to travel several kilometers through the ice. You can recognize a muon that is traveling at nearly the speed of light by a cone that follows it. This cone is similar to a boat creating waves behind itself. Looking inside the light cone, you can see its structure.

The muon emits almost undetectably weak, blue light rays outward from its sides. Taken together, all these emitted rays form a hollow cone behind the muon. In the darkness of the Antarctic ice, this glow can be detected up to 100 m away. The AMANDA detector, frozen in a depth of 1500 to 2000 m, is optimized in order to see this light. AMANDA is built out of powerful light sensors, which are packed into pressure-resistant glass spheres. Several hundred of these, attached to steel cables, have been placed more than a mile deep into the ice of the South Pole, where they watch for these small cones of light.

When a muon flies through the AMANDA detector, each light sensor registers the passing cone of light within one billionth of a second. The sensors convert the light into electrical signals, which travel to the surface of the Earth.

The laboratory for AMANDA is at the South Pole, as is its computer control center, which stores and processes the data. Scientists at the center supervise the data recording and do the initial analysis on it. Complex computer programs investigate the chronological order and intensity of the signals. From this information, scientists can calculate the most important information: which direction the initial neutrino came from.

Several hundred neutrino reactions have been detected in trial phases of the past years. In January, 2000, scientists and engineers were able to finish the second phase of AMANDA's expansion. There are now 670 light sensors in the ice, and in a few years, a much larger telescope with 5000 light sensors will be built.

What will the physicists discover? Huge energy-jets that generate cosmic irradiation? The origin of the dark material? The birth of a supernova? Or something totally different, something not found in the catalog of their expections?

Nature almost always shows more imagination than the minds of physicists. What surprises will the cosmos bring them through AMANDA?

back to AMANDA main page | Back to "The Hunt for Neutrinos"

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