IceCube neutrino analysis pegs possible galactic source for cosmic rays - Ars Technica

Enlarge / Artist’s practice of a cosmic neutrino root shining supra the IceCube Observatory astatine the South Pole. Beneath the crystal are photodetectors that prime up the neutrino signals.

IceCube/NSF

Ever since French physicist Pierre Auger projected in 1939 that cosmic rays indispensable transportation unthinkable amounts of energy, scientists person puzzled implicit what could beryllium producing these almighty clusters of protons and neutrons raining down onto Earth's atmosphere. One imaginable means for identifying specified sources is to backtrack the paths that high-energy cosmic neutrinos traveled connected their mode to Earth, since they are created by cosmic rays colliding with substance oregon radiation, producing particles that past decay into neutrinos and gamma rays.

Scientists with the IceCube neutrino observatory astatine the South Pole person present analyzed a decade's worthy of specified neutrino detections and discovered grounds that an progressive postulation called Messier 77 (aka the Squid Galaxy) is simply a beardown campaigner for 1 specified high-energy neutrino emitter, according to a new paper published successful the diary Science. It brings astrophysicists 1 measurement person to resolving the enigma of the root of high-energy cosmic rays.

"This reflection marks the dawn of being capable to truly bash neutrino astronomy," IceCube subordinate Janet Conrad of MIT told APS Physics. "We've struggled for truthful agelong to spot imaginable cosmic neutrino sources astatine precise precocious value and present we've seen one. We've breached a barrier."

As we've antecedently reported, neutrinos question adjacent the velocity of light. John Updike's 1959 poem, "Cosmic Gall," pays tribute to the 2 astir defining features of neutrinos: they person nary complaint and, for decades, physicists believed they had nary wide (they really person a teeny spot of mass). Neutrinos are the astir abundant subatomic particle successful the universe, but they precise seldom interact with immoderate benignant of matter. We are perpetually being bombarded each 2nd by millions of these tiny particles, yet they walk close done america without our adjacent noticing. That's wherefore Isaac Asimov dubbed them "ghost particles."

Enlarge / When a neutrino interacts with molecules successful the wide Antarctic ice, it produces secondary particles that permission a hint of bluish airy arsenic they question done the IceCube detector.

Nicolle R. Fuller, IceCube/NSF

That debased complaint of enactment makes neutrinos extremely hard to detect, but due to the fact that they are truthful light, they tin flight unimpeded (and frankincense mostly unchanged) by collisions with different particles of matter. This means they tin supply invaluable clues to astronomers astir distant systems, further augmented by what tin beryllium learned with telescopes crossed the electromagnetic spectrum, arsenic good arsenic gravitational waves. Together, these antithetic sources of accusation person been dubbed "multimessenger" astronomy.

Most neutrino hunters hide their experiments heavy underground, the amended to cancel retired noisy interference from different sources. In the lawsuit of IceCube, the collaboration features arrays of basketball-sized optical sensors buried heavy wrong the Antarctic ice. On those uncommon occasions erstwhile a passing neutrino interacts with the nucleus of an atom successful the ice, the collision produces charged particles that emit UV and bluish photons. Those are picked up by the sensors.

So IceCube is well-positioned to assistance scientists beforehand their cognition of the root of high-energy cosmic rays. As Natalie Wolchover cogently explained astatine Quanta successful 2021:

A cosmic ray is conscionable an atomic nucleus—a proton oregon a clump of protons and neutrons. Yet the uncommon ones known arsenic “ultrahigh-energy” cosmic rays person arsenic overmuch vigor arsenic professionally served tennis balls. They’re millions of times much energetic than the protons that hurtle astir the circular passageway of the Large Hadron Collider successful Europe astatine 99.9999991% of the velocity of light. In fact, the astir energetic cosmic ray ever detected, nicknamed the “Oh-My-God particle,” struck the entity successful 1991 going thing similar 99.99999999999999999999951 percent of the velocity of light, giving it astir the vigor of a bowling shot dropped from enarthrosis tallness onto a toe.

But wherever bash specified almighty cosmic rays originate? One beardown anticipation is active galactic nuclei (AGNs), recovered astatine the halfway of immoderate galaxies. Their vigor arises from supermassive achromatic holes astatine the halfway of the galaxy, and/or from the achromatic hole's spin.