detectors into the ice cap||
Most telescopes look up. This one looks down. Most capture some sort of light. This one
seeks an invisible subatomic particle. Most telescopes are in remote locations, but this
one goes to extremes: it is buried under more than a mile of ice at the South Pole.|
The Antarctic Muon and Neutrino Detector Array
(AMANDA) is the world's largest detector of the mysterious neutrino--and the first that
can claim to be an astronomical instrument rather than a physics experiment. It trades
sensitivity for the sheer size needed to catch a meaningful number of high-energy neutrinos
from distant objects, which include many of the violent felons on astronomers' most wanted
list: the swirling gas around black holes, the innards of stellar explosions, the
decomposition of the unidentified matter that dominates our cosmos.
So far the observatory, a $7-million collaboration among U.S., Belgian, Swedish and German
universities, consists of 424 glass orbs, each the size of a basketball. They watch for the
eerie blue glow indirectly emitted when neutrinos collide with atomic nuclei in the ice or
underlying rock. The orbs point downward so that Earth will screen out extraneous particles.
To deploy them, workers first used pressurized hot water to melt a column of ice half a
meter across and 2,400 meters deep. Then they lowered in the orbs, strung on a cable like
beads on a necklace, and let them freeze in place. Ultimately, scientists want 5,000 orbs
on 80 cables throughout a cubic kilometer of ice.
It turns out that ice is a friendly place for neutrino detectors. At depth it is
crystal-clear, so the orbs can spot flashes of light hundreds of meters away. AMANDA
exemplifies a new breed of telescope that has redefined what it means to "see."
Image: University of Wisconsin; (inset) The Amanda Collaboration
Back to Article