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A tiny collision beneath the South Pole just changed how we see the universe

Scientists have traced a ghostly particle in Antarctic ice back to its source nearly 4 billion light-years away. Here's how that could change everything.

icecube

In this artist's rendering, based on a real image of the IceCube Lab at the South Pole, a distant source emits neutrinos that are detected below the ice by IceCube sensors, called DOMs.

IceCube/NSF

Scientists using data from a detector embedded in a huge block of ice at the South Pole have traced an eerie and elusive particle back to one of the most powerful objects in existence. In the process, they've unlocked a whole new way to look at the universe. 

The IceCube Neutrino Observatory in Antarctica in September detected a neutrino, which is a rather wild subatomic particle that travels near the speed of light and passes right through almost anything in its path like a ghost. The observatory almost instantly triggered an alert for other telescopes to check certain coordinates for a possible source.

NASA's Fermi Gamma-ray Space Telescope and the Major Atmospheric Gamma Imaging Cherenkov (MAGIC) Telescope in the Canary Islands both identified the same source of the wayward high-power particle: a flare of high-energy cosmic rays shooting into space from a distant supermassive black hole, a powerful phenomenon also known as a blazar

This particular blazar is named TXS 0506+056 and located about 4 billion light-years from Earth in a galaxy that's not visible with the naked eye but is in the direction of the constellation Orion.

"What's special ... is we are in the beam. It is pointing at us," said senior IceCube scientist Albrecht Karle in a news release on Monday.

This is the first time a neutrino has been traced back to its source, and it's a big deal because it represents a new, third way for scientists to observe and measure the universe. 

Up until just a few years ago, we spent centuries seeing the cosmos using only light in all its forms, from radio waves to the visible spectrum on up to X-rays and gamma rays. In 2015, scientists made the Nobel Prize-winning detection of gravitational waves, which are ripples in space-time predicted by Albert Einstein. This allows us to not only see distant objects across space, but to also "feel" the vibrations sent in our direction by massive cosmic events. Scientists call this "multi-messenger astronomy."

Neutrinos now provide us with a third, more spooky way of observing the universe because they are neither light nor gravitational waves, but something else, almost a sort of extra-sensory perception for astrophysicists, for lack of a better metaphor. 

Drexel University assistant professor Naoko Kurahashi Neilson explains the new tool neutrinos provide scientists in terms of a flashlight:

"If I shine a light on a table, you won't see the light on both sides," she explained in a statement. "But with a neutrino flashlight, it will go through and you can see it on both sides."  

Neilson is lead author on one of two papers on the discovery to be published in Friday's edition of the journal Science.

The work also goes a long way toward solving a long-standing mystery: What massive energy source could possibly be blasting rays of these energetic particles across the expanse of everything that is?

"It is interesting that there was a general consensus in the astrophysics community that blazars were unlikely to be sources of cosmic rays, and here we are," says Francis Halzen, the lead scientist for the IceCube Neutrino Observatory. "Now, we have identified at least one source that produces high-energy cosmic rays."

The process of detecting a neutrino is almost as mind-boggling as the insane amount of energy required to launch it on a straight-line path across billions of light-years. 

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

IceCube Collaboration/NSF

So far as anyone knows, the only thing that a neutrino interacts with is an atomic nucleus, and such collisions are rare. Detecting a neutrino would require an awful lot of nuclei in a relatively small area. The solution was the IceCube Neutrino Observatory, which transformed a cubic kilometer of pure, clear ice beneath the South Pole into a massive detector. 

As former IceCube spokesperson Olga Botner explained at a National Science Foundation press conference on the discovery Thursday, the observatory comprises a billion tons of ice, which contains 100 undecillion atoms. (An undecillion is a 1 with 36 zeros behind it.)

A highly energetic neutrino struck one of the nuclei of those frozen water atoms on Sept. 22, 2017, creating a particle called a muon that then moved through the chilled detector, allowing scientists to determine the direction from which the neutrino had arrived at the South Pole. This information was relayed to other observatories to search for the source and the rest is history, quite literally. 

The lasting result is a new way to see and study some of the most inconceivably powerful forces in the universe. It's better than X-ray vision, which astronomers have already had for decades. Rather, it's a key to unlock the more ghostly side of astrophysics. What we'll find there could inform new discoveries for decades to come. 

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