Astronomers Pinpoint Source of High-Energy Neutrinos for First Time - World Truth


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Friday, July 13, 2018

Astronomers Pinpoint Source of High-Energy Neutrinos for First Time

A large multinational team of astronomers has found the first evidence of a source of super-energetic neutrino particles: a distant blazar — the nucleus of a giant elliptical galaxy that fires off particles in massive jets of elementary particles — about 4 billion light-years from Earth.

An artist’s impression of a blazar. Image credit: DESY / Science Communication Lab.

Neutrinos are uncharged subatomic particles that normally pass by the trillion through our bodies and every part of the Earth every second, but they rarely interact with matter — a fact that makes them difficult to detect.

“Neutrinos at these very high energies are formed after cosmic ray particles are accelerated (boosted to very high energy) and interact with other particles,” said Dr. Gary Hill, a researcher at the University of Adelaide.

“So what we’ve found is not only the first evidence of a neutrino source, but also evidence that this galaxy is a cosmic ray accelerator.”

“It is interesting that there was a general consensus in the astrophysics community that blazars were unlikely to be sources of cosmic rays, and here we are,” said University of Wisconsin-Madison Professor Francis Halzen.

“Now, we have identified at least one source that produces high-energy cosmic rays because it produces cosmic neutrinos. Neutrinos are the decay products of pions. In order to produce them you need a proton accelerator.”

Researchers from NSF’s IceCube Neutrino Observatory at the Amundsen-Scott South Pole Station announced the first solid evidence for high-energy neutrinos coming from beyond our Milky Way Galaxy in 2013.

“Now we have found the first evidence for a specific source object, a blazar, which is a very high energy type of galaxy,” Dr. Hill said.

“This blazar, designated TXS 0506+056, is about 4 billion light years from Earth.”

This image shows the sky in gamma rays with energies greater than 1 billion electron volts across a broad region centered on TXS 0506+056, located about 4 billion light-years away. The image shows the number of gamma rays detected during 8 months prior to the onset of the blazar’s flaring activity in April 2017. Brighter colors indicate greater numbers of gamma rays. The brightest sources in the scene are in our own galaxy: the Crab Nebula and its pulsar (top center) and the supernova remnant IC 443, also known as the Jellyfish Nebula (top left). Image credit: NASA / DOE / Fermi LAT Collaboration.

Although not visible to the naked eye, TXS 0506+056 is situated in the night sky just off the left shoulder of the constellation Orion.

This blazar is the source of a high-energy neutrino (IceCube-170922A) detected on September 22, 2017 by the IceCube Observatory.

A signature feature of blazars is twin jets of light and elementary particles that shoot like laser beams from the poles on the axis of the black hole’s rotation.

Equipped with a nearly real-time alert system triggered when neutrinos of the highest energies crash into an atomic nucleus in or near the IceCube detector, the observatory — in less than a minute after the initial detection — relayed coordinates to telescopes worldwide for follow-up observations.

Around twenty space- and ground-based observatories responded to IceCube’s alert.

NASA’s Fermi Gamma-ray Space Telescope, Major Atmospheric Gamma Imaging Cherenkov Telescope (MAGIC) in the Canary Islands, and the High Energy Stereoscopic System (H.E.S.S.) in Namibia detected a flare of high-energy gamma rays associated with TXS 0506+056, a convergence of observations implicating the blazar as the most likely source.

On September 22, 2017, the IceCube Neutrino Observatory, represented in this illustration by strings of sensors under the ice, detected a high-energy neutrino that appeared to come from deep space. NASA’s Fermi Gamma-ray Space Telescope (top left) pinpointed the source as a supermassive black hole in the galaxy TXS 0506+056. Image credit: NASA / Fermi / Aurore Simonnet, Sonoma State University.

“This result heralds a new era for neutrino astronomy, and opens up the long-anticipated linkages with observations using photons or light, such as gamma-rays and radio waves,” said Dr. Gavin Rowell, a scientist with the University of Adelaide and a member of the H.E.S.S. team.

“We’re beginning to do astronomy using means other than light, combining electromagnetic (light) observations with other measurements in what we now call multimessenger astronomy,” said Dr. Marcos Santander, from the University of Alabama.

“This is the first evidence that we have of an active galaxy emitting neutrinos, which means we may soon start observing the Universe using neutrinos to learn more about these objects in ways that would be impossible with light alone.”

“The era of multi-messenger astrophysics is here,” said Dr. France C√≥rdova, Director of the National Science Foundation.

“Each messenger — from electromagnetic radiation, gravitational waves and now neutrinos — gives us a more complete understanding of the Universe, and important new insights into the most powerful objects and events in the sky. Such breakthroughs are only possible through a long-term commitment to fundamental research and investment in superb research facilities.”

The findings are published in two papers in the journal Science.


The IceCube Collaboration, Fermi-LAT, MAGIC, AGILE, ASAS-SN, HAWC, H.E.S.S., INTEGRAL, Kanata, Kiso, Kapteyn, Liverpool Telescope, Subaru, Swift/NuSTAR, VERITAS, VLA/17B-403 teams. 2018. Multimessenger observations of a flaring blazar coincident with high-energy neutrino IceCube-170922A. Science 361 (6398): eaat1378; doi: 10.1126/science.aat1378

The IceCube Collaboration. 2018. Neutrino emission from the direction of the blazar TXS 0506+056 prior to the IceCube-170922A alert. Science 361 (6398): 147-151; doi: 10.1126/science.aat2890