Published: Mon, July 16, 2018
Science | By

Neutrino particle gives scientists new understanding of universe

Neutrino particle gives scientists new understanding of universe

However, scientists have been able to define two separate sources for these particles in the past: the supernova 1987A and our own sun.

High-energy neutrinos are produced by the same sources as cosmic rays, the highest-energy particles ever observed, but differ in a key respect, said University of Wisconsin physicist and IceCube Neutrino Observatory lead scientist Francis Halzen.

Data gathered by NSF's IceCube Neutrino Observatory at the foundation's Amundsen-Scott South Pole Station in Antarctica point to an answer to a more than century-old riddle about the origins of high-energy cosmic rays. Just 44 seconds later, an alert went out to the entire astronomical community. It is the only all-sky, real-time variability survey in existence.

"Neutrino astronomy offers us a very different view of the universe than we get from other types of telescopes", said Tyce DeYoung, a professor of physics at Michigan State University. "When you combine the additional information that there's a blazar in that exact same spot that's flaring at the same time", Wood says, there's suddenly a less than 1 percent chance the neutrino in question came from anywhere other than the blazar.

The ability to use particles like high-energy neutrinos in astronomy enables a more robust examination, much as the confirmation of ripples in the fabric of space-time called gravitational waves, announced in 2016, opened another new frontier in astronomy.

Jamie Yang Savannah Guthrie  IceCube  NSF
The July 2018 cover of Science features neutrinos
Jamie Yang Savannah Guthrie IceCube NSF The July 2018 cover of Science features neutrinos

Neutrinos are called ghost particles because they are incredibly small and hard to detect. Where do they come from?

There, 19 telescopes saw a distant galaxy occupied by a supermassive black hole called a blazar. This means that these particles pass right through thousands of planets, stars, and even humans at almost the speed of light.

Although not originally high on the list of potential cosmic neutrino sources, this makes for strong evidence that blazars do generate the elusive particles. However, unlike the electrically charged particles of cosmic rays, neutrinos are electrically neutral and therefore not deflected by cosmic magnetic fields as they travel through space, meaning that the direction from which they arrive points straight back at their actual source. Because they rarely interact with matter and have almost no mass - hence their nickname "ghost particle" - neutrinos travel nearly undisturbed, giving scientists an almost direct pointer to their source.

Associate Professor Gary Hill, from the University of Adelaide's School of Physical Sciences, said, "So what we've found is not only the first evidence of a neutrino source but also evidence that this galaxy is a cosmic ray accelerator". The solution of this problem was the IceCube Neutrino Observatory, which can transform a cubic kilometre of clear, pure ice below the South Pole into an enormous detector. When a neutrino interacts with the nucleus of an atom, it creates a secondary charged particle, which, in turn, produces a characteristic cone of blue light that is detected by IceCube and mapped through the detector's grid of photomultiplier tubes. At the time the neutrino was detected, it did not record any burst of gamma rays from the location of the blazar, so scientists were able to rule out prompt emissions from certain sources, such as a gamma-ray burst.

Astronomers said the discovery could provide a long sought clue to one of the enduring mysteries of physics and the cosmos. TXS 0506+056 is a type of quasar known as a blazar, in which our line of sight from Earth is along the jet - right down the gun barrel. "Up to this day, we didn't know where they originated", says Elisa Resconi from the Technical University of Munich, whose group contributed crucially to the findings. "This also emphasizes the critical role that telescopes in Hawaiʻi play in that community", said Shappee.

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