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HomescienceIceCube neutrino analysis links possible galactic source of cosmic rays

IceCube neutrino analysis links possible galactic source of cosmic rays


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Zoom / Artistic representation of a cosmic neutrino source shining over the IceCube Observatory in Antarctica. Under the ice are optical detectors that pick up neutrino signals.

IceCube / NSF

Since the French physicist Pierre Auger proposed in 1939 who – which cosmic rays They must carry huge amounts of energy, and scientists have puzzled over what could produce these powerful clusters of protons and neutrons that rain down on Earth’s atmosphere. One possible means of identifying such sources is to undo the paths high-energy cosmic neutrinos take on their way to Earth, since they arise from cosmic rays colliding with matter or radiation, resulting in particles that then decay into neutrinos and gamma rays.

Scientists with ice Cube The Antarctic Neutrino Observatory has now analyzed a decade’s worth of these neutrino discoveries and found evidence that an active galaxy called Messier 77 (also known as the Squid Galaxy) is a strong candidate for a single high-energy neutrino emitter, according to a new paper Published in the journal Science. It brings astrophysicists one step closer to solving the mystery of the origin of high-energy cosmic rays.

“This observation represents the dawn of the ability to actually do neutrino astronomy,” Janet Conrad, an IceCube member from MIT APS Physics. “We’ve struggled for a long time to see potential cosmic neutrino sources of very high interest and now we’ve seen one. We’ve broken a barrier.”

as such Notify us earlierAnd the neutrinos Travel near the speed of light. John Updike’s 1959 poem, “Cosmic gal“praises the two most defining features of neutrinos: They have no charge, and for decades, physicists thought they had no mass (they actually have very little mass). Neutrinos are the most abundant subatomic particles in the universe, but they rarely interact with any A kind of material.We are constantly bombarded every second by millions of these tiny particles, yet they pass right through us without us noticing them.That is why Isaac Asimov called them “ghost particles”.

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When neutrinos interact with particles in clear Antarctic ice, they produce secondary particles that leave a trail of blue light as they travel through the IceCube detector.
Zoom / When neutrinos interact with particles in clear Antarctic ice, they produce secondary particles that leave a trail of blue light as they travel through the IceCube detector.

Nicole R. Fuller, IceCube/NSF

This low rate of reaction makes neutrinos It is very difficult to detect, but because it is so light, it can escape unimpeded (and thus largely unaltered) by colliding with other matter particles. This means they could provide valuable clues to astronomers about distant systems, bolstered by what can be learned with telescopes across the electromagnetic spectrum, as well as gravitational waves. Together, these various sources of information have been called “Multiple Messenger” astronomy.

Most neutrino hunters bury their experiments deep in the earth, and it is better to cancel out loud interference from other sources. In the case of the IceCube, the collaboration features arrays of basketball-sized optical sensors buried deep in Antarctica’s ice. On those rare occasions when a transient neutrino interacts with the nucleus of an atom in the ice, the collision produces charged particles that emit ultraviolet light and blue photons. These are captured by sensors.

So IceCube is well positioned to help scientists advance their knowledge of the origin of high-energy cosmic rays. Like Natalie Wolcoffer convincingly Explained in Quanta In 2021:

A cosmic ray is just an atomic nucleus – a proton or a group of protons and neutrons. However, rare cosmic rays known as “ultra-energy cosmic rays” have just as much energy as professionally served tennis balls. They are millions of times more energetic than the protons orbiting around the circular tunnel of the Large Hadron Collider in Europe at 99.9999991% of the speed of light. In fact, the most energetic cosmic ray ever discovered, dubbed a “Oh my God particle,” hit the sky in 1991 at 99.9999999999999999999951 per cent of the speed of light, giving it the energy of a bowling ball that fell from shoulder height to toe height. .

But where do such powerful cosmic rays originate? One of the strong possibilities Active Galactic Nuclei (AGNs), found in the middle of some galaxies. Its energy originates from the supermassive black holes at the center of the galaxy, and/or from the rotation of the black hole.

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