We Finally Know Where the Highest Energy Cosmic Rays are Coming From: Blazars

blazar

Way out there in space is a class of objects called blazars. Think of them as extreme particle accelerators, able to marshall energies a million times stronger than the Large Hadron Collider in Switzerland. It turns out they’re the culprits in one of the great astrophysical mysteries: what creates and propels neutrinos across the universe at blazingly fast speeds? It turns out that the answer’s been there all along: blazars pump out neutrinos and cosmic rays. That’s the conclusion a group of astronomers led by Dr. Sara Buson of Universität Wurzburg in Germany came to as they studied data from a very unique facility here on Earth: the IceCube Neutrino Observatory in Antarctica.

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Experiment Finds no Sign of Sterile Neutrinos

Could sterile neutrinos be a fourth kind of neutrino? Credit: IceCube - University of Wisconsin

We don’t know what dark matter is. We do know the characteristics of dark matter, and much of how it behaves, so we know what physical properties dark matter must have, but no known matter has all the necessary characteristics of dark matter. So we’re stumped.

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Astronomers Track a Neutrino Back to the Source. Where a Black Hole Tore Apart a Star

Neutrinos are notoriously finicky particles.  Hundreds of trillions pass through a person’s body every second, yet they hardly seem to interact with anything (though they actually do a lot).  Even more hard to find are the “high energy” neutrinos that are believed to be formed as the outcome of some of the most violent events in the universe.  Now, researchers using NASA’s Swift telescope have found a high energy neutrino for the first time from one type of those ultra-violent events – a tidal disruption.  But something was a little bit off about it.

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Almost all High-Energy Neutrinos Come From Quasars

The IceCube Neutrino Observatory at the South Pole. It detected neutrinos and helped astronomers trace them to blazars. Credit: Emanuel Jacobi/NSF.
The IceCube Neutrino Observatory at the South Pole. It detected neutrinos and helped astronomers trace them to blazars. Credit: Emanuel Jacobi/NSF.

Buried under the ice at the South Pole is a neutrino observatory called IceCube. Every now and then IceCube will detect a particularly high-energy neutrino from space. Some of them are so high energy we aren’t entirely sure what causes them. But a new article points to quasars as the culprit.

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Neutrinos Have a Newly Discovered Method of Interacting With Matter, Opening up Ways to Find Them

SCGSR Awardee Jacob Zettlemoyer, Indiana University Bloomington, led data analysis and worked with ORNL’s Mike Febbraro on coatings, shown under blue light, to shift argon light to visible wavelengths to boost detection. Credit: Rex Tayloe/Indiana University

The neutrino is a confounding little particle that is believed to have played a major role in the evolution of our Universe. They also possess very little mass, have no charge, and interact with other particles only through the weak nuclear force and gravity. As such, finding evidence of their interactions is extremely difficult and requires advanced facilities that are shielded to prevent interference.

One such facility is the Oak Ridge National Laboratory (ORNL) where an international team of researchers are conducting the COHERENT particle physics experiment. Recently, researchers at COHERENT achieved a major breakthrough when they found the first evidence of a new kind of neutrino interaction, which effectively demonstrates a process known as coherent elastic neutrino-nuclear scattering (CEvNS).

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Neutrinos Have Played a Huge Role in the Evolution of the Universe

Computer simuations show how neutrinos can form cosmic clumps. Credit: Yoshikawa, Kohji, et al

It’s often said that we haven’t yet detected dark matter particles. That isn’t quite true. We haven’t detected the particles that comprise cold dark matter, but we have detected neutrinos. Neutrinos have mass and don’t interact strongly with light, so they are a form of dark matter. While they don’t solve the mystery of dark matter, they do play a role in the shape and evolution of our universe.

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Neutrinos prove the Sun is doing a second kind of fusion in its core

The central nylon balloon of the Borexino Detector. Credit: The Borexino Collaboration

Like all stars, our Sun is powered by the fusion of hydrogen into heavier elements. Nuclear fusion is not only what makes stars shine, it is also a primary source of the chemical elements that make the world around us. Much of our understanding of stellar fusion comes from theoretical models of atomic nuclei, but for our closest star, we also have another source: neutrinos created in the Sun’s core.

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Astronomers are ready and waiting to detect the neutrino blast from a nearby supernova explosion like Betelgeuse

One of the Daya Bay detectors. Roy Kaltschmidt, Lawrence Berkeley National Laboratory

When giant stars die in impressive supernova blasts, about 99% of the energy released goes into producing a flood of neutrinos. These tiny, ghostly particles slip through tons of matter like it’s not even there. But a new generation of detectors will be able to catch them, telling us of the inner machinations of the deaths of stars.

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Detecting the Neutrinos From a Supernova That’s About to Explode

A composite image of SN 1987A from Hubble, Chandra, and ALMA. Image Credit: By ALMA (ESO/NAOJ/NRAO)/A. Angelich. Visible light image: the NASA/ESA Hubble Space Telescope. X-Ray image: The NASA Chandra X-Ray Observatory - http://www.eso.org/public/images/eso1401a/, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=30512379

Neutrinos are puzzling things. They’re tiny particles, almost massless, with no electrical charge. They’re notoriously difficult to detect, too, and scientists have gone to great lengths to detect them. The IceCube Neutrino Observatory, for instance, tries to detect neutrinos with strings of detectors buried down to a depth of 2450 meters (8000 ft.) in the dark Antarctic ice.

How’s that for commitment.

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