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Ghost particles crashing into Antarctica reveal the unseen heart of a nearby galaxy

Ghost particles crashing into Antarctica reveal the unseen heart of a nearby galaxy

About 47 million light-years from where you sit, the center of the black hole-filled galaxy NGC 1068 is spewing streams of enigmatic particles. These “neutrinos”, otherwise known as the notoriously elusive “ghost particles”, haunt our universe but leaves little trace of their existence.

Immediately after their formation, bundles of these invisible bits plunge across the cosmic expanse. They zoom past the bright stars we can see and pass pockets of space full of wonders we have yet to discover. They fly and fly and fly until they occasionally crash into a detector deep below the Earth’s surface.

The neutrino’s journey is seamless. But scientists are patiently waiting for them to arrive.

Tucked away in about a billion tons of ice, more than 2 kilometers (1.24 miles) beneath Antarctica, lies IceCube Neutrino Observatory. A neutrino hunter, you might call it. When any neutrino transports its party to the cold continent, IceCube is ready.

In the newspaper published Friday in the journal Science, the international team behind this ambitious experiment has confirmed that it has found evidence of 79 “high-energy neutrino emissions” coming from around NGC 1068, opening the door to new – and endlessly fascinating – types of physics. “Neutrino astronomy,” scientists call it.

It would be a branch of astronomy that can do what existing branches simply cannot.

The starry sky shows the heart of the Milky Way.  On the ground is the Antarctic surface covered with snow on which the structure rests.

A front view of the IceCube Lab at dusk, with a starry sky showing views of the Milky Way overhead and sunlight lingering on the horizon.

Martin Wolf, IceCube/NSF

Before today, physicists only showed neutrinos coming from both Suns; the atmosphere of our planet; a chemical mechanism called radioactive decay; supernovae; and — thanks to the first IceCube progress in 2017 — a blazar, or a ravenous supermassive black hole headed directly for Earth. A void called TXS 0506+056.

With this newly discovered neutrino source, we are entering a new era of the particle story. In fact, according to the research team, it is likely that the neutrinos originating from NGC 1068 have up to millions, billions, perhaps even trillion the amount of energy held by sun-rooted neutrinos or supernovae. These figures are astonishing because, generally speaking, such ghostly parts are so powerful, yet evasive, that every second, trillions upon trillions of neutrinos move right through your body. You just don’t know.

And if you want to stop a neutrino in its tracks, you should fight it with a block of lead one light year – although even then there would be little chance of success. Therefore, harnessing these particles, NCG 1068 version or not, could allow us to penetrate regions of the cosmos that would normally be out of reach.

What now?

Not only is this moment massive because it gives us more evidence of a strange particle that hasn’t even been announced exists until 1956but also because neutrinos are like keys behind the scenes of our universe.

They possess the ability to detect phenomena and solve puzzles that we cannot solve in any other way, which is the primary reason why scientists are trying to develop neutrino astronomy.

“The universe has multiple ways of communicating with us,” Denise Caldwell of the National Science Foundation and a member of the IceCube team told reporters Thursday. “Electromagnetic radiation, which we see as starlight, gravitational waves that shake the fabric of space – and elementary particles, such as protons, neutrons and electrons, ejected by localized sources.

“One of these elementary particles is neutrinos that permeate the universe, but unfortunately, neutrinos are very difficult to detect.”

In fact, even the galaxy NGC 1068 and its supermassive black hole are usually obscured by a thick veil of dust and gas, making them difficult to analyze with standard optical telescopes and equipment—despite years of scientists trying to pierce its veil. NASA The James Webb Space Telescope could have a leg up in this case because of his infrared eyesbut neutrinos might be an even better way.

Expected to be generated behind such opaque screens that filter our universe, these particles can carry cosmic information behind those screens, zoom across great distances while having essentially no other matter, and deliver pristine, pristine information to humanity about the elusive corners of the universe.

“We are very lucky, in a way, because we can access an incredible understanding of this object,” Elisa Resconi, of the Technical University of Munich and a member of the IceCube team, told NGC 1068.

an ice cube

In this artist’s rendering, based on an actual image of the IceCube laboratory at the South Pole, a distant source emits neutrinos that are detected under the ice by IceCube’s sensors, called DOMs.

IceCube/NSF

It is also notable that there are many (many) more galaxies similar to NGC 1068 — categorized as Seyfert galaxies — but there are blazars similar to TXS 0506+056. This means that the latest IceCube discovery is probably a bigger step forward for neutrino astronomers than the observatory’s original discovery.

Perhaps most of the neutrinos propagating through the universe are rooted in the NGC 1068 doubles. But in the grand scheme of things, the merit of neutrinos is much more than just their sources.

These ghosts, said Justin Vandenbroucke of the University of Wisconsin-Madison and a member of the IceCube team, are capable of solving two great mysteries in astronomy.

For one thing, many galaxies in our universe have gravitationally monstrous voids at their centers, black holes that reach masses millions to billions of times the mass of our Sun. And these black holes, when active, emit jets of light from their guts — emitting enough luminosity to outshine every single star in the galaxy itself. “We don’t understand how it happens,” Vandenbrouke said simply. Neutrinos could provide a way to study the region around black holes.

The second is general but persistent, the cosmic ray puzzle.

We don’t really know where cosmic rays come from either, but these particle streams reach energies up to and over millions of times higher than what we can reach here on Earth with man-made particle accelerators such as the one at CERN.

“We think neutrinos have a role,” Vandenbroucke said. “Something that can help us answer these two mysteries of black holes powering very bright galaxies and the origin of cosmic rays.”

A decade to catch a handful

To be clear, IceCube doesn’t exactly capture neutrinos.

Basically, this observatory tells us every time a neutrino happens to interact with the ice surrounding it. “Neutrinos barely interact with matter,” Vandenbrouke emphasized. “But they do communicate sometimes.”

As millions of neutrinos shoot into the icy region where the IceCube is placed, at least one tends to hit an ice atom, which then shatters and produces a flash of light. IceCube sensors pick up that flash and send a signal to the surface, alerts that are then analyzed by hundreds of scientists.

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A rendering of the IceCube detector shows the interaction of a neutrino with an ice molecule.

IceCube Collaboration/NSF

Ten years of light-flash data allowed the team to largely determine where each neutrino came from in the sky. It soon became clear that there was a dense neutrino region located exactly where the galaxy NGC 1068 was stationed.

But even with such evidence, Resconi said the team knew “it’s not time to pop the champagne, because we still have one fundamental question to answer. How many times has this alignment happened by chance? How can we be sure the neutrinos are actually coming from such a facility?”

A diagram from IceCube of the latest sky results.  It shows where neutrinos seem to come from across the universe and pinpoints the densest locations as sources.

Map of the sky scanning for point sources in the Northern Hemisphere, showing where the neutrinos appear to come from across the universe. The circle of NGC 1068 also coincides with the overall hottest spot in the northern sky.

IceCube Collaboration

So to make things as specific as possible and really, really prove that this galaxy is spewing out ghosts, “we generated 500 million times the same experiment,” Resconi said.

After which, I can only imagine, a bottle of Veuve finally popped out. Although the hunt is not over.

“We are just beginning to scratch the surface in terms of finding new sources of neutrinos,” said Ignacio Taboada of the Georgia Institute of Technology and a member of the IceCube team. “There must be many other sources far deeper than NGC 1068, hiding somewhere.”



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