What does the "letter" from Cygnus mean? What is the significance of Russo's great discovery?

On May 17, the Institute of High Energy Physics of the Chinese Academy of Sciences and the Nature Journal Publishing Group jointly released a major discovery. my country's national major scientific and technological infrastructure high-altitude cosmic ray observatory Lasso has discovered a large number of ultra-high-energy cosmic accelerators in the Milky Way. And recorded the highest 1.4-beat electron-volt gamma photon from the constellation Cygnus, marking the beginning of the era of ultra-high-energy gamma astronomy.

First, two points of misunderstanding that may be reminiscent of alien civilizations are explained. Many news headlines use the word letter, and the letter here should of course be in quotation marks, because it is definitely not an alien in the constellation Cygnus who really sent us a message. It is a kind of cosmic ray, so it can also be understood as a natural information such as electromagnetic waves. There is also the discovery of a large number of ultra-high-energy cosmic accelerators in the Milky Way, and the accelerators here sound like some kind of equipment. In fact, it refers to a kind of production mechanism, a kind of way or celestial body that can accelerate particles to very high energies.

Then we explain a few related concepts. What exactly is this cable in our country? It is a cosmic ray observatory located at high altitudes. Cosmic rays are also called cosmic rays. It is a high-energy charged particle from space. When the ray is still outside the atmosphere and has not interacted with the atmosphere, it is called a primary cosmic ray. It is mainly composed of high-energy photons, that is, gamma rays, as well as protons and electrons. When photons and protons enter the atmosphere, they interact with atomic nuclei in the air, producing many secondary particles. These secondary particles then continue to interact with the air to generate new secondary particles, and so on in a cascade, with the number of particles increasing exponentially throughout the process. This phenomenon is called extensive atmospheric showers.

In addition to measuring particles in extended atmospheric showers, Lasso can also detect the Cherenkov radiation produced by particles in the air. Cherenkov radiation says that a type of electromagnetic radiation is emitted when certain particles travel faster in a medium than light travels in that medium. Because of the shorter wavelength of this radiation, it is bluish. Its principle is a bit similar to a sonic boom, so some people call it a light boom. Why detect it? Because it is difficult to determine the location of the ray source only by extensive atmospheric showers, this is because the vast majority of cosmic ray particles are charged. As they travel through space, they are deflected by the magnetic fields of various celestial bodies. That is to say, starting from the emission source, it may have to go through an "eighteen bends in the mountain road" before reaching the earth, so it is difficult for us to directly trace its source. But fortunately, there are also uncharged high-energy photons that are emitted together. These photons are basically heading straight for us, except for some bending caused by gravitational lensing. Therefore, as long as we determine the source of the gamma rays, it becomes much easier to find the corresponding sources of other particles. Of course, there are other detection methods for the cable, which will not be discussed here. In short, the cable is actually measured by a variety of methods.

In addition, what does this 1.4 beat electron volt mean? First of all, electron volt, it is an energy unit, that is, electron volt, which represents the kinetic energy obtained by an electron after being accelerated by a potential difference of one volt. As you can imagine, this is a very small unit, so the beat electron volt is also called pev, which stands for 10 to the 15th electron volt. What is the concept of 1.4Pev? The largest particle accelerator ever built by humans is the LHC at CERN. It can only accelerate a small number of particles to around 0.01Pev at best. It can be considered that for a long period of time, humans have been unable to conduct PEV-level research based on experiments. So more and more theories like string theory are hard to verify experimentally. High-energy physics for us humans may still be low-energy physics in the eyes of advanced civilizations.

After understanding the above concepts, let's talk about why this discovery is considered very important. The first and most important keyword of this discovery is ultra-high energy. The high-energy rays discovered before are at the Tev level at most, and the existence of pev cosmic rays in the Milky Way has always been only a theoretical guess. And this time, in the actual observation, it was officially discovered that there is indeed a high-energy ray emission source above the pev in the Milky Way. This will directly open the era of ultra-high-energy gamma astronomy, and it is expected that more and more new ray sources will be discovered in the future.

In addition to ultra-high energy, the second keyword found this time is more. With its strong performance, Lasso discovered 12 ultra-high-energy gamma-ray sources in the Milky Way in just 11 months of data. And I have to mention that the cable is actually still in the construction stage and not all completed. That is to say, in this breakthrough discovery, Lasso did not show its full strength.

In addition, the third keyword of this issue is accurate, because it is easy to detect rays, but it is not easy to locate the source of rays. Unlike previous diffuse photons, the 12 sources discovered this time are basically directional. They are speculated to come from the young, massive clusters in Cygnus, the star-forming regions. There are also supernova remnants such as the Crab Nebula, and the pulsar wind cloud in the center. However, the exact formation of the rays, that is, how the particles are accelerated to such high energies, is still unclear and requires further study.

For these high-energy ray sources in the universe, they are like natural laboratories. I just said that the ability of artificial high-energy particles is limited, so these ray sources are equivalent to a kind of natural particle accelerator. Studying them can indeed help us understand and It is also possible to understand the universe, and even say that it will become the key to breaking through the current bottleneck of basic physics in the future. What do you think of this?