About 47 million light-years from where you are, the center of a black hole-laden galaxy called NGC 1068 spews streams of enigmatic particles. These ‘neutrinos’, also known as the notoriously elusive ‘ghost particles’, haunt our universe, leaving little trace of their existence.
Immediately after they arise, bundles of these invisible bits plunge across the cosmic expanse. They flash past bright stars we can see and rustle past space pockets full of wonders yet to be discovered. They fly and fly and fly until they occasionally bump into a detector deep below the Earth’s surface.
The neutrinos’ journey is seamless. But scientists are patiently waiting for them to arrive.
Nestled in about 1 billion tons of ice, more than 2 kilometers (1.24 miles) below Antarctica, lies the IceCube Neutrino Observatory. You could call it a neutrino hunter. When neutrinos transfer their group to the icy continent, IceCube is ready.
In a paper published Friday in the journal Science, the international team behind this ambitious experiment confirms that they have found evidence of 79 “high-energy neutrino emissions” from the vicinity of NGC 1068, opening the door to new — and endlessly fascinating — kinds of physics. “Neutrino astronomy,” scientists call it.
It would be a branch of astronomy that can do what existing branches just can’t.
Before today, physicists had only shown neutrinos coming from the sun; the atmosphere of our planet; a chemical mechanism called radioactive decay; supernovas; and – thanks to IceCube’s first breakthrough in 2017 – be a blazar, or voracious supermassive black hole directly on Earth. A void called TXS 0506+056.
With this newly discovered neutrino source, we are entering a new era of the particle story. According to the research team, neutrinos originating from NGC 1068 are likely to reach millions, billions, maybe even trillions the amount of energy held by neutrinos rooted in the sun or supernovae. Those are staggering numbers, because such ghostly bits are generally so powerful yet elusive that trillions and trillions of neutrinos pass right through your body every second. You just can’t say.
And if you wanted to stop a neutrino in its tracks, you’d have to fight it with a block of lead a light-year wide — although even then there would be a fractional chance of success. So by exploiting these particles, the version of NCG 1068 or not, we might be able to penetrate areas of the cosmos that are normally beyond our reach.
This moment is huge not only because it gives us more evidence of a strange particle that was only announced in 1956, but also because neutrinos are like keys to the backstage of our universe.
They have the ability to reveal phenomena and solve puzzles we can’t solve any other way, which is the main reason scientists are trying to develop neutrino astronomy in the first place.
“The universe has multiple ways to communicate with us,” Denise Caldwell of the National Science Foundation and a member of the IceCube team told reporters on Thursday. “Electromagnetic radiation, which we see as light from stars, gravitational waves that shake the fabric of space — and elementary particles, such as protons, neutrons and electrons spewed out from local sources.
“One of these elementary particles are neutrinos that permeate the universe, but unfortunately neutrinos are very difficult to detect.”
Even the galaxy NGC 1068 and its giant black hole are typically obscured by a thick veil of dust and gas, making them difficult to dissect with standard optical telescopes and equipment — despite years of scientists trying to break through the curtain. NASA’s James Webb Space Telescope could have an edge in this case because of its infrared eyes, but neutrinos could be an even better way to get in.
They are expected to be generated behind such opaque screens that filter our universe, these particles can carry cosmic information from behind those screens, zoom over great distances while interacting with essentially no other matter, and deliver pristine, pristine information to humanity. across elusive corners of space.
“We’re very lucky in a way, because we have access to a great understanding of this object,” Elisa Resconi, of the Technical University of Munich and IceCube team member, said of NGC 1068.
It’s also noteworthy that there are many (much) more galaxies similar to NGC 1068 — categorized as Seyfert galaxies — than there are blazars similar to TXS 0506+056. This means IceCube’s latest discovery is a bigger step forward for neutrino astronomers than the observatory’s groundbreaking one.
Perhaps most of the neutrinos spreading through the universe are rooted in NGC 1068 lookalikes. But overall, there’s a lot more to neutrinos’ merit than just their sources.
These ghosts, as Justin Vandenbroucke of the University of Wisconsin-Madison and an IceCube team member put it, are capable of solving two great mysteries in astronomy.
First, a wealth of galaxies in our universe flaunt gravitationally monstrous voids at their centers, black holes millions to billions of times larger than those of our sun. And these black holes, when active, blast rays of light from their guts — emitting enough light to outshine every single star in the galaxy itself. “We don’t understand why that is,” said Vandenbrouke simply. Neutrinos could be a way to study the regions around black holes.
Second, there is the common but persistent mystery of cosmic rays.
We don’t really know where cosmic rays come from either, but these arrays of particles reach energies millions of times higher than we can achieve here on Earth with human-constructed particle accelerators like the one at CERN.
“We think neutrinos may play a role,” Vandenbroucke said. “Something that could help us answer these two mysteries of black holes that power very bright galaxies and of the origin of cosmic rays.”
A decade to catch a handful
To be clear, IceCube doesn’t actually capture neutrinos.
Basically, this observatory tells us every time a neutrino interacts with the ice that envelops it. “Neutrinos hardly interact with matter,” Vandenbrouke emphasized. “But they do have contact sometimes.”
As millions of neutrinos shoot into the icy region where IceCube is set up, at least one tends to collide with an ice atom, which then disintegrates, producing a flash of light. IceCube sensors catch that flash and send the signal to the surface, reports that are then analyzed by hundreds of scientists.
Ten years of flash data enabled the team to virtually map where each neutrino appears to be coming from in the sky. It soon became apparent that there was a dense region of neutrino emissions right where the galaxy NGC 1068 is stationed.
But even with such evidence, Resconi said the team knew that “it is not the time to open the champagne, because we have one more fundamental question to answer. How many times has this alignment happened? How can we be sure that neutrinos are actually come from such an object?”
So, to make things as concrete as possible, and really, really prove that this galaxy is spewing ghosts, “we generated the same experiment 500 million times,” Resconi said.
To which, I can only imagine, a bottle of Veuve was finally popped. Although the hunt is not over yet.
“We’re just beginning to surface in terms of finding new sources of neutrinos,” said Ignacio Taboada of the Georgia Institute of Technology and IceCube team member. “There must be many other wells, much deeper than NGC 1068, hiding somewhere to be found.”