First neutrino image of an active galaxy

For more than ten years, the IceCube observatory in Antarctica has been monitoring the luminous traces of extragalactic neutrinos. While evaluating data from the observatory, an international research team led by the Technical University of Munich (TUM) discovered a source of high-energy neutrino radiation in the active galaxy NGC 1068, also known as name of Messier 77.

The universe is full of mysteries. One of these mysteries involves active galaxies with gigantic black holes located at their center. “Today, we still don’t know exactly what processes are taking place there,” explains Elisa Resconi, professor of experimental physics with cosmic particles at TUM. Today, his team has taken a big step towards solving this enigma: astrophysicists have discovered a source of high-energy neutrinos in the spiral galaxy NGC 1068.

It is very difficult to study the active centers of galaxies using telescopes that detect visible light or gamma or X-ray radiation from space, because clouds of cosmic dust and hot plasma absorb the radiation. Only neutrinos can escape from the hells at the edges of black holes; these neutrinos have no electric charge and almost no mass. They pass through space without being deflected by electromagnetic fields or absorbed. This makes them very difficult to detect.

The biggest hurdle in neutrino astronomy so far has been separating the very weak signal from the loud background noise created by particle impacts from Earth’s atmosphere. It took many years of measurements using the IceCube neutrino observatory and new statistical methods for Resconi and his team to accumulate enough neutrino events for their discovery.

Detective work in eternal ice

The IceCube telescope, located in the ice of Antarctica, has been detecting light traces resulting from incident neutrinos since 2011. Glauch. “Statistical evaluation shows a very significant cluster of neutrino impacts originating from the direction of the active galaxy NGC 1068. This means that we can assume with near certainty probability that the high-energy neutrino radiation originates from this galaxy.”

The spiral galaxy, 47 million light-years away, was discovered as early as the 18th century. NGC 1068 – also known as Messier 77 – resembles our galaxy in shape and size, but has a very bright center that is brighter than the entire Milky Way, although the center has only approximately the size of our solar system. This center contains an “active nucleus”: a gigantic black body with a mass of about one hundred million times that of our sun, which absorbs large quantities of matter.

But how and where are neutrinos generated there? “We have a clear script,” Resconi says. “We believe that high-energy neutrinos are the result of an extreme acceleration that matter in the vicinity of the black hole experiences, raising it to very high energies. We know from experiments at particle accelerators that High-energy protons generate neutrinos when they collide with other particles. In other words: we have found a cosmic accelerator.”

Neutrino observatories for a new astronomy

NGC 1068 is the statistically largest source of high-energy neutrinos to be discovered to date. More data will be needed to be able to locate and study fainter, more distant neutrino sources, says Resconi, who recently launched an international initiative to build a multi-cubic-kilometre neutrino telescope in the northeast Pacific. , the Pacific Ocean. Neutrino experiment, P-ONE. Together with the planned second generation IceCube Observatory – IceCube Gen2 – it will provide the data for the neutrino astronomy of the future.