Hubble image of the spiral galaxy NGC 1068. Credit: NASA / ESA / A. van der Hoeven
An international team of scientists has discovered evidence of high-energy neutrino emission from the galaxy NGC 1068 for the first time. First spotted in 1780, NGC 1068, also known as Messier 77, is a active galaxy in the constellation Cetus and one of the best-known and best-studied galaxies to date. Located 47 million light-years from us, this galaxy can be observed with large binoculars. The results, to be published today (November 4, 2022) in the journal Sciencewere shared yesterday during an online science webinar that brought together experts, journalists and scientists from around the world.
Physicists often call the neutrino the “ghost particle” because they almost never interact with other matter.
The detection was made at the IceCube Neutrino Observatory. This enormous neutrino telescope, which is supported by the National Science Foundation, encompasses 1 billion tons of instrumented ice at depths of 1.5 to 2.5 kilometers (0.9 to 1.2 miles) below the surface of the Earth. Antarctica near the South Pole. This unique telescope explores the farthest reaches of our universe using neutrinos. He reports the first sighting of a high energy astrophysical neutrino source in 2018. The source is a known blazar named TXS 0506+056 located 4 billion light-years from the left shoulder of the constellation Orion.
“A neutrino can distinguish a source. But only an observation with multiple neutrinos will reveal the dark core of the most energetic cosmic objects,” says Francis Halzen, professor of physics at the University of Wisconsin-Madison and principal investigator of IceCube. He adds: “IceCube has accumulated some 80 neutrinos of teraelectronvolt energy from NGC 1068, which are not yet enough to answer all of our questions, but they are certainly the next big step towards the realization of neutrino astronomy.”
When a neutrino interacts with molecules in Antarctica’s transparent ice, it produces secondary particles that leave a trail of blue light as they pass through the IceCube detector. Credit: Nicolle R. Fuller, IceCube/NSF
Unlike light, neutrinos can escape in large numbers from extremely dense environments in the universe and reach Earth largely undisturbed by the matter and electromagnetic fields that permeate extragalactic space. Although scientists envisioned neutrino astronomy more than 60 years ago, the weak interaction of neutrinos with matter and radiation makes their detection extremely difficult. Neutrinos could be the key to our questions about how the most extreme objects in the cosmos work.
“Answering these far-reaching questions about the universe we live in is a primary goal of the US National Science Foundation,” says Denise Caldwell, director of the NSF’s Physics Division.
This video illustrates how IceCube neutrinos gave us our first glimpse into the inner depths of the active galaxy, NGC 1068. Credit: Video by Diogo da Cruz, with sound by Fallon Mayanja and voice by Georgia Kaw
As is the case with our home galaxy, the[{” attribute=””>Milky Way, NGC 1068 is a barred spiral galaxy, with loosely wound arms and a relatively small central bulge. However, unlike the Milky Way, NGC 1068 is an active galaxy where most radiation is not produced by stars but due to material falling into a
Messier 77 and Cetus in the sky. Credit: Jack Parin, IceCube/NSF; NASA/ESA/A. van der Hoeven (insert)
“Recent models of the black hole environments in these objects suggest that gas, dust, and radiation should block the gamma rays that would otherwise accompany the neutrinos,” says Hans Niederhausen, a postdoctoral associate at Michigan State University and one of the main analyzers of the paper. “This neutrino detection from the core of NGC 1068 will improve our understanding of the environments around supermassive black holes.”
NGC 1068 could become a standard candle for future neutrino telescopes, according to Theo Glauch, a postdoctoral associate at the Technical University of Munich (TUM), in Germany, and another main analyzer.
IceCube detector schematic showing the layout of the strings across the ice cap at the South Pole, and the active detection array of light sensors filling a cubic kilometer volume of deep ice.
“It is already a very well-studied object for astronomers, and neutrinos will allow us to see this galaxy in a totally different way. A new view will certainly bring new insights,” says Glauch.
These findings represent a significant improvement on a prior study on NGC 1068 published in 2020, according to Ignacio Taboada, a physics professor at the Georgia Institute of Technology and the spokesperson of the IceCube Collaboration.
From left to right: Martin Wolf (TUM), Hans Niederhausen (TUM), Elisa Resconi (TUM), Chiara Bellenghi (TUM), Francis Halzen (UW–Madison), and Tomas Kontrimas (TUM). Credit: Yuya Makino, IceCube/NSF
“Part of this improvement came from enhanced techniques and part from a careful update of the detector calibration,” says Taboada. “Work by the detector operations and calibrations teams enabled better neutrino directional reconstructions to precisely pinpoint NGC 1068 and enable this observation. Resolving this source was made possible through enhanced techniques and refined calibrations, an outcome of the IceCube Collaboration’s hard work.”
The improved analysis points the way toward superior neutrino observatories that are already in the works.
“It is great news for the future of our field,” says Marek Kowalski, an IceCube collaborator and senior scientist at Deutsches Elektronen-Synchrotron, in Germany. “It means that with a new generation of more sensitive detectors there will be much to discover. The future IceCube-Gen2 observatory could not only detect many more of these extreme particle accelerators but would also allow their study at even higher energies. It’s as if IceCube handed us a map to a treasure trove.”
The IceCube Collaboration, spring 2022. Credit: IceCube Collaboration
With the neutrino measurements of TXS 0506+056 and NGC 1068, IceCube is one step closer to answering the century-old question of the origin of cosmic rays. Additionally, these results imply that there may be many more similar objects in the universe yet to be identified.
“The unveiling of the obscured universe has just started, and neutrinos are set to lead a new era of discovery in astronomy,” says Elisa Resconi, a professor of physics at TUM and another main analyzer.
“Several years ago, NSF initiated an ambitious project to expand our understanding of the universe by combining established capabilities in optical and radio astronomy with new abilities to detect and measure phenomena like neutrinos and DOI: 10.1126/science.abg3395
The IceCube Neutrino Observatory is funded and operated primarily through an award from the National Science Foundation to the University of Wisconsin–Madison (OPP-2042807 and PHY-1913607). The IceCube Collaboration, with over 350 scientists in 58 institutions from around the world, runs an extensive scientific program that has established the foundations of neutrino astronomy.