Fermi Telescope discovers neutrino's origin as supermassive black hole

Rodiano Bonacci
Luglio 16, 2018

The observations, made by the IceCube Neutrino Observatory at the Amundsen-Scott South Pole Station and confirmed by telescopes around the globe and in Earth's orbit, help resolve a more than a century-old riddle about what sends subatomic particles such as neutrinos and cosmic rays speeding through the universe. As reported by an worldwide research team, the source of this particle lies in a galaxy almost four billion light years away: it is a very big black hole in the constellation of Orion. There are several follow-up observations detailed in a half dozen papers in addition to the two Science papers.

"It's the beginning of a new channel in astronomy", Dolinski said.

The ability to use particles such as high-energy neutrinos in astronomy enables another strong test, as a confirmation of the waves in the space-time clay called gravitational waves, announced in 2016; another new boundary was opened in astronomy.

Scientists discover a new way of looking at the universe during the analysis of the data from a detector located in a huge block of ice from the South Pole.

One way in which scientists expect energetic neutrinos to be created is as a sort of by-product of cosmic rays, that are expected to be produced in cosmic particle accelerators, such as the vortex of matter created by supermassive black holes or exploding stars. Also, neutrinos are scarcely absorbed. Neutrinos are uncharged particles, unaffected by even the most powerful magnetic field.

The neutrino that set off the alarm in 2017 had an energy of some 300 trillion electron volts, by the units of energy and mass that physicists prefer.

"In order to get a measurable signal from the tiny fraction of neutrinos that do interact, neutrino physicists need to build extremely large detectors", explains Dr Susan Cartwright, a particle physicist at the University of Sheffield. For the IceCube detector, an global consortium of scientists headed by the University of Wisconsin in Madison (USA) drilled 86 holes into the Antarctic ice, each 2500 metres deep. Because they travel at almost the speed of light and do not interact with other matter, they are capable of traversing billions of light years.

Until late a year ago, scientists weren't able to detect the source of the inbound neutrinos. It appears they arise from some of the universe's most violent locales. Do such blazars produce all the neutrinos and all the cosmic rays we see?

Because scientists on the IceCube experiment had worked out the path the particle took through their subterranean ice instrument, astronomers knew where in the sky to look for the particle's source.

An artist's conception, based on a real image of the IceCube Lab at the South Pole, a distant source emits neutrinos that are detected below the ice by IceCube sensors. Sure enough, they were able for the first time to assign a celestial object to the direction from which a high-energy cosmic neutrino had arrived.

There, about four billion light years from Earth, they saw a familiar object. The neutrino source may have been a jet that shot out into space as the black hole devoured matter. They also found cosmic rays and gamma rays coming from the same place, confirming their suspicions. "Now we have found key evidence supporting this assumption", Resconi emphasises.

Neutrinos, which originate in the sun, the Earth, and even from the radioactive decay of elements in our own bodies, as well as from sources outside our galaxy, are vastly more abundant than photons.

Two gamma-ray telescopes, NASA's orbiting Fermi Gamma-ray Space Telescope - which had already observed enhanced gamma-ray activity from the direction of the blazar during its regular scans of the entire sky every three hours - and the Major Atmospheric Gamma Imaging Cherenkov Telescopes (MAGIC) in the Canary Islands, looed in the direction provided by NSF's IceCube.

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