IceCube neutrino analysis identifies a possible galactic source of cosmic rays

Zoom / Artist’s view 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 this is cosmic rays They must carry huge amounts of energy, and scientists wondered what could produce these powerful clusters of protons and neutrons that rain down on Earth’s atmosphere. One possible way to identify such sources is to trace the paths that high-energy cosmic neutrinos take on their way to Earth, where they are created by 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 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 such a high-energy neutrino emitter, according to 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,” said Janet Conrad, an Ice Cube Fellow from MIT. APS Physics says. “We have struggled for a long time to see the possible sources of cosmic neutrinos of very high importance and now we have seen one. We have broken a barrier.”

as such We have already informedAnd the neutrinos Travel near the speed of light. John Updike’s 1959 poem, “cosmic bitternessIt commemorates the two most defining features of neutrinos: they have no charge, and for decades physicists thought they had no mass (in fact, they have very little mass). Neutrinos are the most abundant subatomic particles in the universe, but they very rarely interact with any type of matter. We are constantly bombarded every second by millions of these tiny particles, but they pass through us without even noticing them, which is why Isaac Asimov called them “ghost particles”.

When neutrinos interact with particles in the transparent ice in Antarctica, they produce secondary particles that leave a trail of blue light as they pass through the IceCube detector.
Zoom / When neutrinos interact with particles in the transparent ice in Antarctica, they produce secondary particles that leave a trail of blue light as they pass 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 unhindered (and thus largely unaffected) from collisions 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 referred to as “multi-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 involves arrays of basketball-sized optical sensors buried deep in Antarctica’s ice. On the rare occasions that a transient neutrino interacts with the nucleus of an atom in the ice, the collision produces charged particles that emit ultraviolet and blue photons. These are captured by the sensors.

So IceCube is well positioned to help scientists advance their knowledge of the origin of high-energy cosmic rays. Like Natalie Wolchofer with conviction Explained to 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 “extremely high energy” cosmic rays have the same amount of energy as tennis balls served by professionals. They are millions of times more powerful than the protons hurtling around the circular tunnel of the Large Hadron Collider in Europe at 99.999991% 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% of the speed of light, giving it roughly the energy of a bowling ball that fell from shoulder height to a toe. .

But where do these powerful cosmic rays come from? There is a strong possibility Active Galactic Nuclei (AGNs), found in the middle of some galaxies. Its energy comes from supermassive black holes at the center of the galaxy and/or from the black hole’s rotation.

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