Elusive neutrinos caught streaming from black hole hidden in dust
A unique observatory buried in pristine Antarctic ice has detected a stream of elusive neutrino particles emanating from the center of a distant dust-covered galaxy.
Observation by IceCube Observatory at the South Pole is only the second detection of a cosmic source neutrinosand scientists hope it could shed light on what’s going on inside the supermassive black holes.
Neutrinos are weird. They are everywhere, but most of the time they do not interact with other particles or any kind of matter. This is because they have very little mass and no electrical charge. For this reason, they are incredibly difficult to spot. But their complete indifference to their surroundings also means that unlike other particles, they do not deviate from their path, cruising vast distances in straight lines from their sources. This means that once astronomers know how to detect them, they can trace neutrinos to their origins much more easily than other types of particles.
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An international team of scientists has now reported detecting such a neutrino stream from a galaxy known as NGC 1086 (sometimes called Messier 77 or the Squid Galaxy). NGC 1086 is a dusty galaxy, with a shape quite similar to our own milky way. NGC 1086, however, produces bursts stars much faster than our galactic home and orbiting a black hole much more massive than the one at the center of the Milky Way.
This hungry black hole, devouring vast amounts of material, forms the core of a glowing active galactic nucleus that emits bright bursts of high-energy cosmic rays and charged particles that shadow the galaxy’s stars. Most of the black hole’s crackling, however, is hidden from view because the center of the galaxy is hidden by a thick ring when viewed from Earth. Neutrinos, however, with their ability to pass through matter, escape from this ring and reach our planet undisturbed.
“We are peering into the active regions of the galaxy NGC 1068 47 million light-years away,” said Gary Hill, an associate professor of physics at the University of Adelaide in Australia and one of the authors of the paper. statement (opens in new tab). “As we observe the neutrinos it emits, we will be able to learn more about the extreme particle acceleration and production processes taking place inside the galaxy, which has not been possible until now because other high-energy emissions cannot escape from it.”
The detection makes NGC 1068 only the second source of cosmic neutrinos ever identified. In 2018, the IceCube observatory found a neutrino stream coming from the active galactic nucleus of a galaxy known as TXS 0506+056.
That galaxy, located in the constellation Orion, is 100 times farther from Earth than NGC 1068, but emits a jet of material at nearly the speed of light, which is aimed directly at Earth. Therefore, any radiation coming from TXS 0506+056 is much easier to see than from NGC 1068.
“After the excitement in 2018 of the discovery of neutrinos from TXS 0506+056, it is even more exciting to find a source producing the steady stream of neutrinos we can see with IceCube,” Hill said. “The fact that neutrinos can escape from these otherwise darkened regions of space means that they are also difficult to detect.”
The IceCube observatory is a unique installation. It consists of over 5,000 detectors submerged at depths of 0.9 to 1.5 miles (1.5 to 2.5 kilometers) in pristine Antarctic ice. Suspended from 86 vertical cables spaced 410 feet (125 meters) apart, the detectors register tiny flashes of blue light that are triggered when high-energy neutrinos strike the atomic nuclei of ice molecules.
The observatory, built in the 2000s, has been operating since 2010. A recent study analyzed detections of high-energy neutrinos from 2011 to 2020, looking for possible sources of these particles among known active galaxies. Computer modeling has previously suggested that active black holes, like the one at the center of NGC 1068, must be able to accelerate particles and eject them into intergalactic space along with bursts of high-energy radiation. Scientists expect other similar galaxies to produce their own neutrino fluxes.
“A single neutrino can single out a source. But only observations with multiple neutrinos will reveal the darkened core of the most energetic cosmic objects,” Francis Halzen, professor of physics at the University of Wisconsin-Madison and principal investigator of the IceCube project, said in a special statement (opens in new tab). “IceCube has accumulated about 80 teraelectronvolt neutrinos from NGC 1068, which are not yet enough to answer all our questions, but are definitely the next big step towards realizing neutrino astronomy.”
Astronomers are currently planning the second generation of the IceCube detector, which will be able to detect a thousand times more neutrinos and detect five times fainter sources. Gradually, astronomers said, it dimmed the universe will open, ushering in a new era in astronomy.
NGC 1068 could become a “standard candle” for this future neutrino research, Theo Glauch, a postdoctoral fellow at the Technical University of Munich (TUM) in Germany and co-author of the paper, said in a statement. The galaxy, discovered in 1780, is well known to astronomers and has been studied for centuries.
Study (opens in new tab) was published in the journal Science on November 4.
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