Neutrinos on Ice Now the Coolest New Astronomy Tool
A massive telescope buried in the Antarctic ice has detected 28 record-breaking, extremely high-energy neutrinos -- elementary particles that likely originate outside our solar system. The achievement, which comes nearly 25 years after the pioneering idea of detecting neutrinos in ice, provides the first solid evidence for astrophysical neutrinos from cosmic accelerators and has been hailed as the dawn of a new age of astronomy. The team of researchers that detected the neutrinos with the new IceCube Neutrino Observatory in Antarctica, which includes Penn State scientists, will publish a paper describing the detections on 22 November 2013 in the journal Science.
"While it is premature to speculate about the precise origin of these neutrinos, their energies are too high to be produced by cosmic rays interacting in the Earth's atmosphere, strongly suggesting that they are produced by distant accelerators of subatomic particles elsewhere in our galaxy, or even farther away," said Penn State Associate Professor of Physics Tyce DeYoung, the deputy spokesperson of the IceCube Collaboration.
The neutrinos had energies greater than 1,000,000,000,000,000 electron volts or, as the scientists say, 1 peta-electron volt (PeV). Two of these neutrinos had energies many thousands of times higher than the highest-energy neutrino that any man-made particle accelerator has ever produced.
Penn State Professor of Physics and Astronomy and Astrophysics Doug Cowen, who has worked on IceCube for over a decade, said "Scientists have been searching high and low for these super-energetic neutrinos using detectors buried under mountains, submerged in deep lakes and ocean trenches, lofted into the stratosphere by special balloons, and in the deep clear Antarctic ice at the South Pole. To have finally seen them after all these years is immensely gratifying."
Because high-energy neutrinos rarely interact with matter and are not deflected by magnetic fields in our galaxy, they can carry information about the workings of the highest-energy and most-distant phenomena in the universe. But although billions of neutrinos pass through the Earth every second, the vast majority are lower-energy particles that originate either in the Sun or in the Earth's atmosphere. Far rarer are the high-energy neutrinos that more likely would have been created much farther from Earth in the most powerful cosmic events -- gamma ray bursts, black holes, or the birth of stars.
IceCube is comprised of more than 5,000 digital optical modules melted into in a cubic kilometer of ice at the South Pole. The observatory, supported by the U.S. National Science Foundation, detects neutrinos through the fleeting flashes of blue light produced when a neutrino interacts with a water molecule in the ice. The detections of the 28 high-energy neutrino events, including two that exceeded the unprecedented energy level of 1 PeV, are among the main goals for building the IceCube detector.
The IceCube collaboration is continuing to refine and expand the search with new data and new analysis techniques, which may reveal additional high-energy events and possibly point to their astrophysical source or sources. "Although further observations will be required to confirm the extraterrestrial origin of these neutrinos, after more than ten years of work building this detector, it's very exciting to see what may be the first glimpse of a new window on our universe," DeYoung said.
The IceCube Neutrino Observatory was built under a National Science Foundation (NSF) Major Research Equipment and Facilities Construction grant, with assistance from partner funding agencies in Germany, Sweden, and Belgium. Francis Halzen, the Hilldale and Gregory Breit Distinguished Professor of Physics at the University of Wisconsin-Madison, is the principal investigator of the IceCube collaboration. The NSF Division of Polar Programs continues to support the project with a Maintenance and Operations grant, in conjunction with support from international scientific funding agencies. The scientific collaboration includes 250 physicists and engineers from the U.S., Germany, Sweden, Belgium, Canada, Switzerland, Japan, New Zealand, and Australia.
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