China News Service, Beijing, May 14 (reporter
Sun Zifa) Chinese Academy of Sciences National Astronomical Observatory released news to the media on May 14, the station Dr. Xu Jun and Han Jinlin researcher by analyzing the pulsar in the Milky Way and the distribution of the Faraday rotation effect of the radio source outside the Milky Way, the latest research found that the Milky Way’s halo (Milky Way) has a huge magnetic ring structure, its magnetic ring extends from 6000 light years to 50,000 light years from the center of the Milky Way.
Schematic diagram of the structure of the giant magnetic ring in the halo of the Milky Way Galaxy. National Astronomical Observatory of the Chinese Academy of Sciences/Photo by
This landmark research paper by Chinese scientists on the magnetic field of the Milky Way has recently been published in the international scientific journal Astrophysical Journal (ApJ), providing crucial observations for the study of cosmic ray particle propagation, galactic gas dynamics, and cosmic magnetic field evolution.
The first author of the paper, Xu Jun, introduced that the origin and evolution of the cosmic magnetic field is a long-standing major problem in astrophysics, and it is also a priority topic for many large radio telescope projects such as the Square Kilometer Array Radio Telescope (SKA). They are all developing and improving polarization measurement capabilities, hoping to make efforts in this direction.
Among them, measuring the large-scale magnetic field structure of the Milky Way is a rather challenging work. Researcher Han Jinlin, who pioneered this field of research, has been deeply involved in the study of the Milky Way’s magnetic field for the past 30 years. He measured the large-scale magnetic field structure of the Milky Way’s disk region (the Milky Way’s disk) by observing the Faraday rotation effect of large-scale pulsars and extragalactic radio sources. He found that the direction of the large-scale magnetic field in the Milky Way’s disk is along the spiral arms and flipped between the spiral arms.
In the galactic halo region, Han Jinlin and others were the first to certify that the Faraday rotation effect has an antisymmetric sign distribution in the inner galactic sky as early as 1997, indicating that the galactic halo above and below the galactic disk has a circumferential magnetic field structure in the opposite direction, and it was subsequently confirmed by more astronomical observation data. It has been widely adopted by the international astronomical community and has become the basic content of the galactic magnetic field structure model. It has also been written into many international classic textbooks.
Han Jinlin, the corresponding author of the paper, pointed out that the size and strength of the magnetic ring structure of the galactic halo have been difficult to measure for more than 20 years, because pulsars and other celestial bodies in the galactic halo region near the sun also show the anti-symmetric distribution of the Faraday effect. Some international scholars speculate that Faraday objected to whether the sky is dominated by the interstellar medium in the local region of the Milky Way near the sun. "So, does this magnetic ring exist in the entire galactic halo or only in the local area? What is the strength and size of the galactic halo magnetic ring?"
In response to these problems, Han Jinlin innovatively proposed in this study that the measurement of the Faraday rotation rate of pulsars near the sun as the contribution of the local interstellar medium be deducted from the value of the Faraday effect sky distribution of the extragalactic radio source, so that the Faraday rotation effect distribution of the giant silver halo can be obtained. Xu Jun collected all the relevant data and used the 500-meter Aperture Spherical Radio Telescope (FAST), known as the "Chinese Sky Eye", to newly measure many faint pulsars.
After analyzing the data according to this innovative idea, they found that the average Faraday effect over the entire sky exhibits an antisymmetric distribution of galactic coordinates, and that the antisymmetric distribution is no longer limited to the inner galactic region, but fills the entire sky, extending from the central region of the Milky Way to its opposite direction. The results of this study suggest that the magnetic ring in the galactic halo extends from 6,000 light-years from the galactic center to 50,000 light-years (the sun is located about 30,000 light-years). The interstellar medium in the local region near the sun is obviously part of a large magnetic ring, and its basic properties and characteristics are basically the same as those of the large magnetic ring, but its effect is stronger because it penetrates deep into the galactic disk.
"I had this idea more than 20 years ago. I have been slowly accumulating data and finally got it." Han Jinlin said.
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