China News Service, Beijing, July 9th (Reporter Sun Zifa) Following the discovery of the first ultra-high-energy cosmic accelerators in the Milky Way not long ago and the opening of the era of “ultra-high-energy gamma astronomy”, China’s major national scientific and technological infrastructure is under construction. The Altitude Cosmic Ray Observatory (LHAASO, Chinese transliteration nickname "Lasso"), the latest accurate measurement of the brightness of the Crab Nebula, and recorded in the Crab Nebula a gamma of up to 1100 trillion electron volts challenging the theoretical limit radiation.

  These two major scientific research achievements in the field of high energy physics were completed by the "Lasso" international cooperation group led by the Institute of High Energy Physics of the Chinese Academy of Sciences (Institute of High Energy, Chinese Academy of Sciences). "(Science) was released online.

Crab Nebula (picture from NASA).

Photo courtesy of Institute of High Energy, Chinese Academy of Sciences

Measuring the highest energy end energy spectrum of the Crab Nebula radiation

  Cao Zhen, a spokesperson for the "Lasso" International Cooperation Group and a researcher at the Institute of High Energy of the Chinese Academy of Sciences, said that the "Lasso" accurately measured the brightness of the "standard candle" of high-energy astronomy this time, covering an energy range of 3.5 orders of magnitude. Ma Guangyuan has set a new standard.

This "standard candlelight" is the famous celestial Crab Nebula formed by the "guest star" discovered and recorded by Sitianjian of the Song Dynasty after a thousand years of evolution.

  "Lasso" measured the highest energy spectrum of the Crab Nebula's radiation, covering a wide range from 0.0005 to 1.1 beats (1 beat = 1000 trillion) electron volts, which not only confirmed the observation results of other experiments in this range for decades , It also realizes the unprecedented precision measurement of the ultra-high energy zone (0.3-1.1 petavolt), thus setting the brightness standard for the "standard candlelight" of this energy zone.

  The Crab Nebula is about 6,500 light-years away from the Earth. It was born in a super-bright supernova explosion in 1054 AD. It is the first confirmed supernova remnant with clear historical observation records in modern astronomy.

At its center is a pulsar that rotates rapidly at 30 revolutions per second. The high-speed rotating super-strong magnetic field continuously blows a large number of positive and negative electrons in the pulsar's surface magneto around, forming a strong stellar wind with a speed close to the speed of light. .

When the electrons in the stellar wind collide with the external medium, they will be further accelerated to higher energies and produce nebulae that people see.

  The Crab Nebula is one of the few celestial bodies that emits radiation in radio, infrared, optical, ultraviolet, X-ray and gamma-ray bands. A large number of observations and studies have been conducted on its spectrum in history, and it is a very bright and stable source of high-energy radiation. , So it is used as a "standard candle" in multiple bands, that is, a ruler for measuring the radiation intensity of other celestial bodies.

Data map: A panoramic view of the "cable" under construction on the flight from Daocheng to Chengdu.

Photo by China News Agency reporter Sun Zifa

The Crab Nebula has an acceleration energy of 20,000 times as high as artificial

  At the same time, this observation of "Lasso" also recorded gamma radiation photons with an energy of 1.1 beats, that is, 1100 trillion electron volts, which is determined to be only about 1/10 the size of the solar system (about 5000 times the distance between the sun and the earth) There is a powerful electron accelerator in the core area of ​​the Crab Nebula, whose acceleration energy reaches about 20,000 times the highest energy of the electron beam produced by artificial accelerators today, which is close to the acceleration limit allowed by the classical electrodynamics and ideal magnetohydrodynamics theory.

  Among the 12 ultra-high-energy gamma light sources previously discovered by "Lasso", the Crab Nebula is one of the two light sources capable of emitting photon photons, and it is also the only celestial body with a clear source of radiation.

The 1.1-PeV photon measured this time provides direct observational evidence of the existence of the 2.3-PeV electron accelerator, which is better than the largest electron accelerator built by humans on the earth-the European Nuclear Research Center Large Hadron Collider ( The energy of the electron beam generated by the predecessor of the LHC) electron-positron collider (LEP) is about 20,000 times higher.

  Cao Zhen pointed out that because the higher-energy electrons are more likely to lose energy in the magnetic field, the particle acceleration mechanism in the Crab Nebula must be surprisingly efficient to overcome the energy loss of these electrons.

According to the measurement results of the "cable", its acceleration efficiency has reached 15% of the theoretical limit, which is about 1,000 times higher than the acceleration efficiency of the detonation wave generated by the supernova explosion. It is undoubtedly the "standard model" of electron acceleration in high-energy astrophysics. challenge.

"Lasso" is completed this month and will be put into scientific operation

  Experts in the industry said that the latest research results published in Science this time fully demonstrate the ability of the "cable" to cross-check the unique multiple detection methods to ensure the accuracy and reliability of the measurement results.

  The large scientific device "cable", which is constructed and operated and managed by the Institute of High Energy of the Chinese Academy of Sciences, is located in Haizi Mountain at an altitude of 4410 meters in Daocheng County, Sichuan Province. It covers an area of ​​about 1.3 square kilometers and consists of 5195 electromagnetic particle detectors and 1,188 A composite array composed of a one square kilometer ground shower particle array composed of the Muzi detector, a 78,000 square meter water Cherenkov detector array, and 18 wide-angle Cherenkov telescopes arranged alternately.

  "Lasso" uses these four detection technologies to measure the response of cosmic rays or gamma rays in the atmosphere in an all-round, multivariate, and three-dimensional manner, and to reconstruct their basic information.

  Cao Zhen said that the "Lasso" is planned to be completed and put into scientific operation in July 2021, and it is expected that 1-2 electron photons from the Crab Nebula can be recorded every year.

Therefore, in the next few years, more mysteries about the acceleration of electron-electron voltaic particles are expected to be revealed.

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