The first scream of neutrinum astronomy

The other day it was announced that the ICE Cube detector has registered one neutrino of very high energy (at least 180 TEV) from a direction that coincides with the accuracy of half a gradus with one of the blazers (TXS 0506, hereinafter we use the abbreviated name). There are also additional considerations confirming that this Blazar is a source of neutrino.

What is Ice Cube

This is a large Muion detector in Antarctica, his working body is a cubic kilometer of ice. 86 strings are frozen in the ice with photographs of 60 pieces per each, at a depth of 1.5–2.5 km. The object of observation is muons of high energies born from the interaction of neutrino with ice. Muons and products of their interaction with the substance radiate Cherenkovsky light, which spreads in ice by tens of meters and falls into photographs. The accuracy of the restoration of the direction of the Muon is 0.5–0.3 ° depending on energy. The accuracy of energy restoration is quite bad, so the detector sees only part of the track, the loss of muon when interacting with the substance is stochastic, and their dependence on energy is logarithmic. Only the lower limit in energy is determined reliably.

The vast majority of the neutrino recorded by the “ice cube” are atmospheric: the proton flies very high energy, gives rise to a particle cascade in the air, among which there is a neutrino. However, the flow of atmospheric neutrinos quickly decreases with energy. In order to give rise to neutrino, the particle must break up, and with an increase in energy, the decaying base grows, and it is no longer enough - the particle interacts with the substance instead of decay. Therefore, neutrino with very high energy (more than 100 TEV), most likely, flew out of distant space.

Ice Cube registered more than two times more (54 versus 20 ± 6 at the beginning of 2017) of very high energies (more than 30 TEV) than atmospheric showers can give. This excess is called "astrophysical neutrinos."

What is Blazar

Blazar is one of the manifestations of ultra -massive black holes sitting in the centers of galaxies. The most common name for these objects is “Active Galactic Nuclei”. These nuclei shine due to the radiation of a substance pulled into a black hole. This substance forms the so -called accretion disc, which shines in an ultraviolet and X -ray. If the active galactic core is very powerful, it is called the “quasar”. The accretion discs of some quasars shine 10 thousand times brighter than our Galaxy, although such objects are very rare. The Quasars were much more common in the young universe - with a red shift, more than 1, the peak of their prevalence falls on the first 1-4 billion years of the existence of the Universe. We perfectly see them from a distance of several billion light years. Now there are very few of them, but there are active galactic nuclei of moderate power.

The accretion disk is not the only remarkable detail of the active galactic nucleus. There are still jets - jets of larger plasma, expiring perpendicular to the accretion discs along the axis of rotation of the black hole. They move almost at the speed of light, the so-called Lorenz factor Jet usually is 15-20, sometimes higher than 50. The Lorenz factor shows how many times the time in the moving reference system slows down, or how much the energy of the particle mass is necessary to get its complete energy. Due to the large Lorenz factor, everything that Jet particles radiate is directed forward in a cone with a solution of 1/(Lorenz-factor)-a kind of spotlight is obtained. If we get into the beam of this spotlight, we call what we see, Blazar.

And we see quite amazing things. The main flow of energy from the object falls on the hard gamma-band. Gevs, dozens of GEV even hundreds of GWs, a stream of up to millions of lamps of the galaxy in the entire range, if you do not know that this is a floodlight beam, and recount the entire bodily corner. The radiation of Blasars overlaps the entire electromagnetic spectrum and overshadows the parent galaxy.

Blasars are conditionally divided into two classes. More powerful are called Flat Specrtum Radio Quasaras (FSRQ). There is no Russian term. These are rare monsters, but they are also visible from afar with red displacements 3-4, so they make up half of all objects visible in gamma rays. Less powerful are called BL Lacerta (BL of Lizards), abbreviated BL LAC. The Russian lingual term exists - “lacertids”, but is rarely used. They differ not only in lower power, but also by greater radiation rigidity. There is almost no radio and optics, but there is a powerful stream of gamma-quanta of energy in tens and hundreds of GEV. BL LACs are much larger, but they are also visible from smaller distances, from red displacements within 0.5.

Physically, BL LAC and FSRQ differ primarily an accretion mode. The second is quasars during a storm of height. The first is exhausted quasars-a giant black hole in place, but the substances are spent a little, the accretion disc shines weakly, the main energy is apparently taken from previously stored energy of rotation of the black hole. In fsrq jets, high energies particles are “stuck” in a very strong radiation of the accretion disk and its environs. In the Lacceretids, nothing prevents the particles from accelerating to ultra -high energies, so they have long been considered the most likely candidates for sources of particles of ultra -high energies, including neutrinos. If we compare Blasars with accelerators, then FSRQ is a very powerful strong -flower accelerator for moderate energies, BL LAC is an accelerator for huge energy with low intensity. Blazar TXS 0506 is a typical BL LAC, in the observed brightness is one in the first fifty half of BL LACs, but it is quite far for this class of objects. Its red displacement is 0.33, so that the absolute brightness is quite high.

What exactly was registered

On September 22, 2017, ICE Cube registered Muon from neutrino of energy at least 180 TEV (the most probable value is 290 TEE), which coincides with the arrival with TXS 0506 with the accuracy of the plus or minus half the gradus. The probability that this photon will coincide with such an accuracy with this object, ~ 10-5. However, there are no less than a hundred of such Blazarov, which would attract attention, and neutrinos of such energies - about ten. Therefore, the probability that some high-energy neutrino coincides with some fairly bright blazar is about 1/100. This is clearly not enough to apply for the opening.

An indirect confirmation that TXS 0506 is related to the case was that this neutrino coincided with the flash of this object observed in the gamma quanta of high energy. But more strong evidence was given by archival excavations. The authors of the opening checked all the neutrinos that came from this direction (a circle size of a degree around TXS 0506). Mostly there were neutrinos of moderate energies up to 10 TEV, among which atmospheric ones prevail. But at the end of 2014-early 2015, a whole pack of neutrino of energy above the average came from the investigated Piglet. The probability of an accidental appearance of such a pack is approximately 1/3000 (3.5 O ). Together with the neutrino of 2017, this becomes a rather strong certificate to declare the opening of neutrino radiation from this object.

Thus, the birth of neutrinal astronomy, about which the astrophysics of different countries spoke for so long and dreamed!

PS If you include in the concept of “neutrinum astronomy” the registration of solar neutrino (see, for example, https://trv-science.ru/2015/10/20/neutrino-za-shkirku/ ) and neutrino from the supernova SN 1987 A, which gave important information about neutrino, then the birth of neutrinal astronomy took place Dozens of years ago. In this sense, the title of the article is unsuccessful and requires clarification. We are talking about astronomy in the classical sense associated with determining the position of the source in the sky, and of course, this is a breakthrough into a completely new area of ​​energy for neutrino astrophysics - a jump in almost 8 orders of magnitude.

Boris Stern