A ghostly particle that crashed in Antarctica in 2019 has been traced to a black hole that tears a star as it acts as a giant space particle accelerator, a new study has found.
Scientists have studied a type of subatomic particle known as a neutrino, which is generated by nuclear reactions and the radioactive decay of unstable atoms. Neutrinos are extremely light – about 500,000 times lighter than an electron.
Neutrinos have no electric charge and rarely interact with other particles. As such, they can easily glide through matter – a lead worth one light year, equal to about 5.8 trillion miles (9.5 trillion kilometers), would stop only about half of the neutrinos flying through it.
However, neutrinos occasionally hit atoms. When this happens, they emit treacherous flashes that scientists have previously noticed to confirm their existence.
In the new study, the researchers examined an extremely high-energy neutrino they spotted on October 1
“It crashed into the Antarctic ice with remarkable energy of more than 100 teraelectronvolts,” said study co-author Anna Frankovyak, now at the University of Bochum in Germany. “By comparison, this is at least 10 times the maximum particle energy that can be achieved in the world’s most powerful particle accelerator, the Large Hadron Collider.”
Video: A neutrino traced to a black hole, shattering a star
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To find the origin of such a powerful neutrino, scientists traced its path through space. They found that it probably came from the galaxy labeled “2MASX J20570298 + 1412165” in the constellation Dolphin, the dolphin, and is about 750 million light-years from Earth.
About six months before scientists discovered the high-energy neutrino, astronomers witnessed the brightness of this galaxy using the Zwicky Transition Facility on Mount Palomar in California. This light probably came from a black hole shattering a star, the so-called tidal event called “AT2019dsg”.
Researchers have suggested that a star came too close to a supermassive black hole at the center of the galaxy 2MASX J20570298 + 1412165, about 30 million times more massive than the sun. It was then torn by the colossal gravity of the black hole, an extreme version of the way the Moon causes the tides on Earth.
Scientists note that about half of the star’s debris was thrown into space, while the other half settled in a swirling disk around the black hole. As the matter from this dismantled star fell into this disk, it glowed and shone bright enough for astronomers to see from Earth.
Researchers estimate that this neutrino has a chance of only 1 in 500 coinciding with the event. This suggests that scientists may have discovered the first particle traced to a tidal event.
“Theoretical work has long predicted that neutrinos can result from tidal and destructive processes,” study lead author Robert Stein, an astronomer for multimedia manager at Germany’s Electron Synchrotron (DESY) in Zeuthen, Germany, told Space.com. “This work is the first observation to support this claim.” He and his colleagues revealed their findings in detail online on February 21 in the journal Nature Astronomy.
These new discoveries shed light on events with tides, much of which remains unknown. In particular, the researchers suggested that the neutrino came from jets of matter exploding near the accretion disk of a black hole at almost the speed of light, Cecilia Lunardini, a particle astrophysicist at Arizona State University, told Space.com. She and study co-author Walter Winter of DESY detailed their findings online on February 22 in a concomitant study in the journal Nature Astronomy.
Although these relativistic jets probably emit many different types of particles, they are mostly electrically charged particles that deviate from intergalactic magnetic fields before reaching Earth. In contrast, neutrinos (which have no charge) can move in a straight line like light rays from a tidal event.
This discovery marks only the second time that scientists have tracked a high-energy neutrino back to its source, Stein said. For the first time, in 2018, astronomers traced such a neutrino back to the blazer TXS 0506 + 056, a huge elliptical galaxy with a rapidly rotating supermassive black hole in its heart.
“Knowing where high-energy neutrinos come from is a big issue in particle astrophysics,” Stein said. “We now have more evidence that they may be due to tidal events.
One strange aspect of this discovery was how a neutrino was not detected until half a year after the black hole began to engulf the star. This suggests that the tidal event could act as a giant space particle accelerator for months, Stein said.
Although researchers have found only one neutrino from this event in tides, “to find even one, billions and billions must have been generated,” Stein said. “We were lucky to see one.”
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