Neutrinos from a Quasar

[lpetrich]

Neutrino observation points to one source of high-energy cosmic rays | NSF - National Science Foundation
Ghostly particle caught in polar ice ushers in new way to look at the universe | Science | AAAS
Ice reveals a messenger from a blazing galaxy | Science
Multimessenger observations of a flaring blazar coincident with high-energy neutrino IceCube-170922A | Science
Neutrino emission from the direction of the blazar TXS 0506+056 prior to the IceCube-170922A alert | Science

In 2010, a neutrino detector called IceCube was built at the South Pole in the Antarctic ice. It was for detecting very energetic neutrinos that very energetic astrophysical events may produce.

In 2017 September 22, it detected a 260-TeV neutrino, a neutrino with an energy about 40 times greater than a LHC-accelerated proton's kinetic energy.

Using a recently-installed triggering system, two gamma-ray telescopes were turned in the direction of the neutrino's presumed direction of origin. They observed a gamma-ray flare from its direction. From the Fermi gamma-ray satellite's observations, the source was tracked down to a blazar called TXS 0506+056. A blazar is a quasar with a relativistic jet pointed at us, and a quasar is a galaxy-center black hole with lots of material spiraling into it, material that glows *very* bright.

This blazar has a redshift of 0.34, and using Ned Wright's cosmology calculator, its light -- and its gamma rays and neutrinos -- took 3.8 billion years to get here.

The IceCube team looked in their records, and they found 13 more neutrinos from that source from late 2014 and early 2015.

From NSF:

High-energy gamma rays can be produced either by accelerated electrons or protons. The observation of a neutrino, a hallmark of proton interactions, is the first definitive evidence of proton acceleration by black holes.

"Now, we have identified at least one source of cosmic rays because it produces cosmic neutrinos," Halzen said. "Neutrinos are the decay products of pions. In order to produce them, you need a proton accelerator."

From Science magazine ("Ghostly particle"):

A neutrino-producing blazar could also help solve a decades-old mystery in astronomy: Where do the extremely high energy protons and other nuclei that occasionally bombard Earth come from? Known as ultrahigh-energy cosmic rays, these particles have a million times more energy than has ever been produced in an earthbound particle accelerator, but what boosts them to such colossal energies is unknown. Suspects have included neutron stars, gamma ray bursts, hypernovae, and the radiation-spewing black holes at the center of some galaxies, but whatever the source, high energy neutrinos are a likely byproduct. If the IceCube team is right, blazars could be the first confirmed source of these cosmic rays.

Back to NSF:

About 20 observatories on Earth and in space have participated in this discovery. The observations across the electromagnetic spectrum, listed alphabetically by project for the given wavelength, include: gamma-rays by the space missions AGILE, INTEGRAL, and Fermi and ground-based telescopes HAWC in Mexico, H.E.S.S. in Namibia, MAGIC in Spain, and VERITAS in the U.S.; X-rays, optical, and radio radiation by space missions MAXI, NuSTAR, and Swift and ground-based observatories ASAS-SN in Chile and the U.S., GTC in Spain, Kanata in Japan, Kapteyn in Spain and the U.S, Kiso in Japan, Liverpool in Spain, OVRO in the U.S., SALT in South Africa, Subaru in Japan, and VLA in the U.S; and neutrinos by ANTARES in France. These observatories are run by international teams with a total of over a thousand scientists supported by funding agencies in countries around the world. Several follow-up observations are detailed in a few other papers that are also released today.

This neutrino event has been named IceCube-170922A

 

[repoman]

That is a lot of energy for a nearly massless particle. Is this energy simply from relativistic mass taken into account?

What would be the range of how many decimal place 9s there are to this neutrino's velocity (0.99......9 c)? How much time did it experience in the ~3.8 billion years?

Is there a theory as to what specific particle interaction led to this neutrino being produced? It happened in an accretion disk, correct?

 

[lpetrich]

That is a lot of energy for a nearly massless particle. Is this energy simply from relativistic mass taken into account?

Yes, nearly all of it is kinetic energy.

What would be the range of how many decimal place 9s there are to this neutrino's velocity (0.99......9 c)? How much time did it experience in the ~3.8 billion years?

The rest masses of the three flavors of neutrinos are still unknown, though neutrino oscillations give us the differences of the squares of their masses. That suggests masses (small), 0.01 eV, and 0.05 eV, so I will use 0.01 eV. That means that the relativistic (gamma) factor is 3*10^16, and that its speed is c*(1 - 6*10^(-34)) or 1.8*10^(-25) m/s less than c.

That neutrino experienced only 4 seconds between being emitted by that blazar and running into the IceCube detector.

Is there a theory as to what specific particle interaction led to this neutrino being produced? It happened in an accretion disk, correct?

The neutrino was most likely produced by accelerated protons colliding with unaccelerated ones (or either or both being some other nucleus). Such a collision produces a big shower of particles, and most of them decay to other particles until they are unable to decay any further. Some of these decays produce neutrinos, like what was recently observed.