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A ghostly particle that crashed in Antarctica in 2019 has been traced to a black hole tearing apart a star while acting as a giant cosmic particle accelerator, according to a new study.
Scientists have studied a kind of subatomic particle known as a neutrino, which is generated by nuclear reactions and the radioactive decay of unstable atoms. Neutrinos are extraordinarily light – about 500,000 times lighter than the electron.
Neutrinos have no electrical charge and rarely interact with other particles. As such, they can easily squeeze through matter – a light-year of lead, equal to about 5.8 trillion miles (9.5 trillion kilometers), would shut down only about half of the neutrinos. that cross it.
However, neutrinos sometimes strike atoms. When this happens, they emit telltale flashes of light, which scientists have already spotted to confirm their existence.
In the new study, the researchers examined a very high-energy neutrino they spotted on October 1, 2019, using the IceCube Neutrino observatory at the South Pole.
“It crashed into the Antarctic ice with a remarkable energy of over 100 tera-electronvolts,” study co-author Anna Franckowiak, now at the University of Bochum in Germany, said in a statement. “For comparison, that’s 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: Neutrino goes back to the black hole shredding a star
Related: Odd neutrino behavior could explain long-standing antimatter mystery
To uncover the origins of such a powerful neutrino, scientists traced its path through space. They discovered that it probably originated from the galaxy designated “2MASX J20570298 + 1412165” in the constellation Delphinus, the dolphin, and is approximately 750 million light years from Earth.
About six months before scientists detected the high-energy neutrino, astronomers witnessed a glow from this galaxy using the Zwicky Transitional Facility on Mount Palomar in California. This light was likely from a black hole shredding a star, a so-called tidal disturbance event dubbed “AT2019dsg”.
Researchers suggest that a star has come too close to a supermassive black hole at the center of the galaxy 2MASX J20570298 + 1412165, one about 30 million times more massive than the sun. She was then torn apart by the colossal gravity of the black hole, an extreme version of how the moon causes the tides to rise and fall on Earth.
Scientists noted that about half of the star’s debris was thrown into space, while the other half settled in a disc swirling around the black hole. When the material from this dismantled star fell into this disk, it got hotter and shone bright enough that astronomers could see it from Earth.
The researchers estimated that this neutrino had a 1 in 500 chance of coinciding with the event. This suggests that scientists have likely detected the first particle dating back to a tidal disturbance event.
“Theoretical work has long predicted that neutrinos could come from tidal disturbance events,” said lead author of the study Robert Stein, a multi-messenger astronomer at the German Electronic Synchrotron (DESY) in Zeuthen, Germany, at Space.com. “This work is the first observational evidence to support this claim.” He and his colleagues detailed their results online Feb.21 in the journal Nature Astronomy.
(Image credit: ZTF / Caltech Optical Observatories)
These new findings shed light on tidal disturbance events, much of which remains unknown. Specifically, the researchers suggested that the neutrino came from jets of material exploding near the black hole’s accretion disk at near the speed of light, said Cecilia Lunardini, a particle astrophysicist at Arizona State University. She and study co-author Walter Winter at DESY detailed their findings online Feb.22 in a follow-up study in the journal Nature Astronomy.
While these relativistic jets likely spat out many different types of particles, they were mostly electrically charged particles, which are deflected by intergalactic magnetic fields before they can reach Earth. In contrast, neutrinos (which have no charge) can travel in a straight line like light rays from the tidal disturbance event.
The discovery is only the second time scientists have traced a high-energy neutrino to its source, Stein said. The first time, in 2018, astronomers traced such a neutrino to blazar TXS 0506 + 056, a huge elliptical galaxy with a rapidly spinning supermassive black hole at its core.
“Knowing where high-energy neutrinos come from is a big question in particle astrophysics,” said Stein. “Now we have more evidence that they can possibly come from tidal disturbance events.”
A strange aspect of this discovery was how the neutrino was not detected until six months after the black hole began to engulf the star. What this suggests is that the tidal disturbance event can act as a giant cosmic particle accelerator for months, Stein said.
Although the researchers detected only one neutrino from this tidal disturbance event, “for us to detect even one, there must be billions upon billions of was generating, ”Stein said. “We were lucky to see one.”
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