IceCube neutrinos point to long-sought cosmic ray accelerator

IceCube Lab

IceCube neutrinos point to long-sought cosmic ray accelerator

They interact with other matter only by gravity and the so-called weak nuclear force and thus flow through us, Earth and even miles of lead like ghosts.

Neutrinos are uncharged subatomic particles that typically go by the trillion through our bodies and all aspects of the Earth each second, however, they once in a while associated with issue - a reality that makes them hard to identify.

The IceCube Laboratory at the Amundsen-Scott South Pole Station, in Antarctica, is run by the University of Wisconsin-Madison and funded by the National Science Foundation. One of the major goals in building IceCube was to identify the sources of high-energy cosmic neutrinos, and that's one cosmic dream that's at last been achieved. But so much about the ghostly particles, including where they come from, remains unknown.

In this artistic composition, based on a real image of the IceCube Lab at the South Pole, a distant source emits neutrinos.

Follow-up observations with orbiting and ground-based telescopes from around the world soon showed that the neutrino likely was coming from the location of a known cosmic object - a blazar called TXS 0506+056, about 4 billion light-years from Earth. Neutrinos are uncharged particles, unaffected by even the most powerful magnetic fields. Because they interact with matter at only very small subatomic distances and have nearly no mass - hence their nickname "ghost particle" - neutrinos travel in a straight line from where they originate, breezing through planets, stars and entire galaxies, giving scientists a pointer nearly directly to their source.

Jamie Yang Savannah Guthrie  IceCube  NSF
The July 2018 cover of Science features neutrinos
Jamie Yang Savannah Guthrie IceCube NSF The July 2018 cover of Science features neutrinos

Five years ago, IceCube furnished the first evidence of high-energy neutrinos from the depths of outer space. But the powerful cosmic accelerators that produce them will also produce neutrinos. "It's a giant elliptical galaxy with a massive spinning black hole at its core and twin jets of light and high-velocity particles, one of which is aligned towards Earth". Do such blazars produce all the neutrinos and all the cosmic rays we see? The direction from which they directly receive points on their original source.The ice cube neutrinos detector includes 86 holes drilled 8,200 feet (2,500 meters) in Antarctic ice.

Fermi's Large Area Telescope (LAT) observed a large gamma ray emission from that region just when the neutrino arrived. Some of these are called "Oh-My-God particles", because a single particle can smash into the Earth with the force of a 50-plus miles per hour baseball-an object that's more than a trillion trillion times more massive. When those streams are pointed at Earth, like TXS 0506+056 is, these galaxies are dubbed blazars. Collisions between high-energy neutrinos and atomic nuclei are very rare but produce an unmistakable signature - a characteristic cone of blue light that is mapped through the detector's grid of 5,000 photomultiplier tubes.

"We're trying to look for more sources and trying to look for more correlations between neutrinos and photons", Neilson said. By pairing neutrino detections with light observations, scientists will be able to answer questions about distant cataclysms, test theories about the composition of the universe, and refine their understanding of the fundamental rules of physics.

Following the September 22 incident, the IceCube team quickly scoured the detector's archival data and found a flare, or dramatic brightening, of more than a dozen astrophysical neutrinos discovered in late 2014 and early 2015, coincident with the same blazar, TXS 0506+056. In fact, now that they know it's possible, studying neutrinos given off by celestial objects opens a whole new way of looking at the universe.

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