Since the French physicist Pierre Auger proposed in 1939 the cosmic rays Transporting incredible amounts of energy, scientists have pondered what could be creating these powerful clusters of protons and neutrons that are raining down on Earth’s atmosphere. One possible means of identifying such sources is to retrace the paths taken by high-energy cosmic neutrinos on their way to Earth, as they arise from cosmic ray collisions with matter or radiation, producing particles that then decay into neutrinos and gamma rays.
scientists with ice cubes Neutrino Observatory at the South Pole have now analyzed a decade of such neutrino detections and uncovered evidence that an active galaxy was calling messier 77 (aka Squid Galaxy) is according to a. a strong candidate for such a high-energy neutrino emitter 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 marks the beginning of the possibility of actually doing neutrino astronomy,” said MIT’s IceCube member Janet Conrad said APS Physics. “We’ve been struggling for so long to see potential cosmic neutrino sources of very high importance, and now we’ve seen one. We broke a barrier.”
As we have previously reported, neutrinos Travel near the speed of light. John Updike’s 1959 poem, “cosmic bile,” acknowledges the two most important characteristics of neutrinos: they have no charge, and for decades physicists believed they had no mass (they actually have a tiny bit of mass). Neutrinos are the most abundant subatomic particles in the universe. but they very rarely interact with any kind of matter. We are constantly bombarded by millions of these tiny particles every second, yet they pass us without us even noticing. That’s why Isaac Asimov called them “ghost particles”.
This low interaction rate makes neutrinos extremely difficult to detect, but because they are so light, they can escape unhindered (and thus largely unaltered) by collisions with other matter particles. This means they can provide astronomers with valuable clues about distant systems, complemented by what can be learned about the electromagnetic spectrum as well as gravitational waves with telescopes. Collectively, these various sources of information have been referred to as “multimessenger” astronomy.
Most neutrino hunters bury their experiments deep underground to better cancel out loud interference from other sources. In the case of IceCube, the collaboration involves arrays of basketball-sized optical sensors buried deep in the Antarctic ice. In the rare cases where a passing neutrino interacts with the nucleus of an atom in the ice, the collision produces charged particles that emit UV and blue photons. These are recorded by the sensors.
So IceCube is well positioned to help scientists advance their knowledge of the origin of high-energy cosmic rays. Convincing as Natalie Wolchover explained at Quanta in 2021:
A cosmic ray is just an atomic nucleus – a proton, or a collection of protons and neutrons. But the rare ones known as “ultra-high energy” cosmic rays have as much energy as professionally served tennis balls. They are millions of times more energetic than the protons hurtling through the circular tunnel of Europa’s Large Hadron Collider at 99.9999991% the speed of light. In fact, the most energetic cosmic ray ever detected, nicknamed the “Oh my God particle,” hit the sky in 1991 at about 99.99999999999999999999951 percent the speed of light, giving it about the energy of a bowling ball thrown by the Shoulder height was dropped on a toe.
But where do such powerful cosmic rays come from? A strong possibility is active galactic nuclei (AGNs) found at the center of some galaxies. Their energy comes from supermassive black holes at the center of the galaxy and/or from the black hole’s spin.
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