Rare cosmic neutrino traced to star-swallowing black hole

Black hole - KM3NeT

The IceCube Neutrino Observatory, located in the South Pole, has traced a high-energy neutrino back to its origin, which was from a supermassive black hole ripping a star into pieces.

While neutrinos are thought to be one of the most abundant particles in the universe, because of their very less interaction with matter and extremely small rest mass, they’re incredibly hard to detect, especially those high-energy neutrinos from deep space. Although a few dozen of such cosmic neutrinos are detected annually, scientists could only trace one of them back to its birthplace, until now.

The neutrino detector IceCube, which is situated deep beneath the Antarctic ice in the South Pole, tracked down the neutrino back to its birthplace, an active supermassive black hole in a galaxy 750 million light-years away, as per a report by Science.

The discovery reveals major connections between the production of high-energy neutrinos and cosmic rays and such tidal disruption events (TDEs), a phenomenon in which a star gets too close to a black hole and gets ripped apart by its tidal forces. 

Scientists speculate that these rare tidal disruption events could be the major sources for high-energy neutrinos and cosmic rays, acting like natural particle accelerators.

In 2017, IceCube detected a high-energy neutrino, which was traced back to its origin for the first time, which was a blazar, a super bright galaxy whose host is a supermassive, active balck hole that spews out jets of high-energy particles straight to our earth.

The high-energy neutrino was initially detected in October 2019, by the IceCube detector, which uses an array of more than 5000 photon detectors arranged in strings. From the arrival time and the brightness of the flash at each detector, researchers can calculate the direction it came from and whether its source is nearby or deep space. With the help of Zwicky Transient Facility, a telescope situated in California, they found that the particle actually originated from a TDE. 

“When we saw it could be a TDE, we immediately went ‘Wow!’” says lead author Robert Stein of DESY particle physics laboratory in Germany. This TDE was earlier discovered in April of 2019 and was named AT2019dsg. This indicates that the TDE remained active for about 5 months, which came by as a surprise to scientists.

Although this discovery reveals properties of active black holes and of the high-energy particles they create, Stein concedes that there is a one in 500 chance it’s a random coincidence. The neutrino and the TDE are linked only by their position in the sky. “We will have to wait and see if there are additional events,” he says.





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