Peering Down Through A Black Hole's Cosmic Jet Got Earth Hit By Record-Breaking Neutrinos

There is an absolutely incredible cosmic object called PKS 1424+240. It is a blazar, a supermassive black hole that is spewing a jet of plasma at really high speed. This source has been a bit of a puzzle; the material on the jet doesn’t look like it's moving that fast as far as jets are concerned, but it is producing extremely energetic gamma rays, and it is the brightest neutrino-emitting blazar in the sky. Now, astronomers have finally worked out what is going on.

The rest of this article is behind a paywall. Please sign in or subscribe to access the full content.

Thanks to 15 years of high-precision radio observation with the Very Long Baseline Array (VLBA), scientists have realized that we are basically looking down the barrel of the gun when it comes to this supermassive black hole. The jet of this powerful supermassive is only 0.6 degrees from the line of sight between us and the blazar.

“When we reconstructed the image, it looked absolutely stunning,” lead author Yuri Kovalev, Principal Investigator of the ERC-funded MuSES project at the Max Planck Institute for Radio Astronomy (MPIfR), said in a statement. “We have never seen anything quite like it — a near-perfect toroidal magnetic field with a jet, pointing straight at us.”

“This alignment causes a boost in brightness by a factor of 30 or more,” explained Jack Livingston, a co-author at MPIfR. “At the same time, the jet appears to move slowly due to projection effects — a classic optical illusion.”

The radio observation shows that the magnetic field across the jet is either donut-shaped or helical, and it can not only accelerate electrons, which are not too heavy, but also protons to velocities close to the speed of light. That’s how neutrinos are produced. Neutrinos are extremely light particles with no electric charge. They are mostly produced in nuclear reactions, like the fusion of hydrogen in the Sun or radioactive decay.

In space, accelerated protons can hit photons, the particles of light, and produce different particles called pions that decay, releasing neutrinos. These neutrinos are extremely light and hardly interact with matter. You have billions of neutrinos going through every centimeter of your skin every second. Some of them come from blazars and they have then been spotted on special detectors such as IceCube in Antarctica.

“Solving this puzzle confirms that active galactic nuclei with supermassive black holes are not only powerful accelerators of electrons, but also of protons — the origin of the observed high-energy neutrinos,” concluded Kovalev.

The study is published in the journal Astronomy & Astrophysics.