Friday, July 13, 2018

Neutrino Detection Suggests Blazar as Cosmic Ray Source

Article Written By: Kyle Tam


 According to new papers released by researchers using the National Science Foundation's (NSF) Icecube detector at the South Pole, evidence suggests that a blazar is the source of high-energy neutrinos. This blazar, a giant elliptical galaxy with a massive spinning black hole at its core, was first singled out by a neutrino alert on September 22, 2017.
 Cosmic neutrinos are ghostly subatomic particles that are capable of travelling unhindered for billions of lights years from the most extreme environments in the universe to Earth. On the other hand, cosmic rays are highly energetic charged particles. Their paths are difficult to trace back to their source because the powerful magnetic fields that fill space warp their trajectories. Yet the source of these rays also produce neutrinos.
  “The evidence for the observation of the first known source of high-energy neutrinos and cosmic rays is compelling,” said Francis Halzen, a University of Wisconsin–Madison professor of physics and the lead scientist for the IceCube Neutrino Observatory.
 When the neutrino alert was sent out on September 22, telescopes worldwide were on high alert for follow-u observatories. From telescopes such as NASA"s Fermi Gamma-ray Space Telescope to the Major Atmospheric Gamma Imaging Cherenknov Telescope in the Canary Islands, a flare of high0energy gamma rays was detected originating from the blazar, implicating the galaxy as the most likely source.
"Fermi was the first telescope to identify enhanced gamma-ray activity from TXS 0506+056 within 0.06 degrees of the IceCube neutrino direction," stated the press released from IceCube. "In a decade of Fermi observations of this source, this was the strongest flare in gamma rays, the highest-energy photons. A later follow-up by MAGIC detected gamma rays of even higher energies."
“Fermi has been monitoring some 2,000 blazars for a decade, which is how we were able to identify this blazar as the neutrino source,” said Regina Caputo, the analysis coordinator for the Fermi Large Area Telescope collaboration. “High-energy gamma rays can be produced either by accelerated electrons or protons. The observation of a neutrino, which is a hallmark of proton interactions, is the first definitive evidence of proton acceleration by black holes.”

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Image: Artist's impression of neutrino interacting in the NSF's IceCube detector via Nicolle R. Fuller/NSF/IceCube

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