Icy telescope spots hot neutrinos

Scientists have unveiled the first glimpse of the sky by a telescope that detects high-energy neutrinos. By spotting extremely energized neutrinos that emerge from the universe’s most violent events, such as collisions between black holes, the new telescope is expected to provide unprecedented insights into such distant phenomena. It can also view high-energy subatomic particles that come from cosmic-ray collisions with atoms in Earth’s atmosphere.

SUBATOMIC SPRINKLES. Clues to distant cosmic cataclysms may lurk in this first sky map of high-energy neutrino sightings. AMANDA Project

The telescope is the Arctic Muon and Neutrino Detector Array II (AMANDA II)–a collection of hundreds of sensitive photodetectors sunk deep into the South Pole ice (SN: 3/27/99, p. 207: https://foogue.com/sn_arc99/3_27_99/note7.htm). After high-energy neutrinos pass through Earth from north to south, some strike atoms in the ice and produce streaks of blue light. By sensing those streaks, the telescope in effect peers through Earth at the northern sky.

Previously, scientists using other underground detectors have been able to study only relatively low-energy neutrinos from such sources as atmospheric collisions and the sun (SN: 12/14/02, p. 371: Identity Check: Elusive neutrinos morph on Earth, as in space).

AMANDA II’s first year of data indicates that nearly all the neutrinos seen were of atmospheric, not deep-space, origin. Because the map correlates to distributions of low-energy, atmospheric neutrinos collected at other detectors, the new telescope is working properly, says AMANDA II team member Francis L. Halzen of the University of Wisconsin–Madison.

Closer scrutiny of the map, plus analysis of 2 years worth of more-recent observations, may reveal hints of more-exciting sources, he adds. The scientists presented their map to a meeting of the International Astronomical Union in Sydney, Australia, on July 15.

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