Using an internationally organized astronomical dragnet, scientist have for the first time located a source of high-energy cosmic neutrinos. The joint observation campaign was triggered by a single neutrino that had been recorded by the IceCube neutrino telescope at the South Pole, on 22 September 2017. The discovery brings good news for neutrinodetector KM3NeT as well. Dorothea Samtleben, Nikhef researcher for ANTARES/Nikhef: “Finding this single source is a major milestone for neutrino astronomy.”
Telescopes on earth and in space were able to determine that a high-energy neutrino had originated in a galaxy nearly four billion light years away, in the constellation of Orion, where a gigantic black hole serves as a natural particle accelerator. Scientists from the 18 different observatories involved are presenting their findings in the journal Science. Furthermore, a second analysis, also published in Science, shows that other neutrinos previously recorded by IceCube came from the same source. Neutrinos are ghostly elementary particles that travel billions of light years through the universe, flying unaffected through stars, planets and entire galaxies.
The observation campaign is a decisive step towards solving a riddle that has been puzzling scientists for over 100 years, namely that of the precise origins of so-called cosmic rays, high-energy subatomic particles that are constantly bombarding Earth’s atmosphere. “We are opening a new window into the high-energy universe,” says Marek Kowalski, head of Neutrino Astronomy at the German accelerator center DESY. “The concerted observational campaign using instruments located all over the globe is also a significant achievement for the field of multi-messenger astronomy.” Multi-messenger astronomy is the investigation of cosmic objects using different messengers, such as electromagnetic radiation, gravitational waves and neutrinos.
This campaign started when IceCube provided a public alert of a very high-energetic neutrino in September 2017, which happened to be within weeks of a gamma-ray flaring alert for the same direction on the sky. A large number of astronomical facilities scrutinized the region in which the high-energy neutrino had originated, scanning the entire electromagnetic spectrum: from high-energy gamma- and X-rays, through visible light, to radio waves. Sure enough, for the first time they were able to assign a celestial object to the direction from which the neutrino had arrived. The active galaxy that has now been identified is a so-called blazar, an active galaxy whose jet points precisely in our direction.
Researchers from ANTARES, the neutrino detector in the Mediterranean Sea, also helped in the search. Nikhef researcher Dorothea Samtleben is point source search coordinator at ANTARES: “This is a major milestone for the field of neutrino astronomy, I am very happy. So far only a diffuse flux of cosmic neutrinos has been seen, no single source identified. This discovery brings good news to KM3NeT, the successor of ANTARES, for the future searches for cosmic neutrino sources.”
Nikhef researcher Paul de Jong, programme leader of the KM3NET group: “The source of this high-energy neutrino is probably a supermassive black hole, sucking in an enormous amount of material. We had long suspected that these black holes produce neutrinos. Now, we are finally sure. That is great news for KM3NeT, where we will further investigate sources like this.”
The ANTARES researchers checked their data during the time of the alert. Samtleben: “We have a lower sensitivity in the part of the sky where the blazar is. We did not find a neutrino signal. We also performed a dedicated analysis of the blazar direction in 11 years of data (2007-2017), whereby the best fit yields a signal of one neutrino, still this is not a significant detection.” The ANTARES analysis paper will be submitted to the Astrophysical Journal Letters, and appear on arXiv.
Source: DESY Press release
More information
Website IceCube
DESY Press release
Results ANTARES
Blog by Daan van Eijk (University of Wisconsin- Madison), former Nikhef researcher (in Dutch)
Reference
Multimessenger observations of a flaring blazar coincident with high-energy neutrino IceCube-170922A; IceCube, Fermi-LAT, MAGIC, AGILE, ASAS-SN, HAWC, H.E.S.S, INTEGRAL, Kapteyn, Kanata, Kiso, Liverpool, Subaru, Swift, VERITAS, VLA
Science, 2018; DOI: 10.1126/science.aat1378
Neutrino emission from the direction of the blazar TXS 0506+056 prior to the IceCube-170922A alert; IceCube Collaboration
Science, 2018; DOI: 10.1126/science.aat2890
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Paul de Jong
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