"China's Sky Eye" (FAST) has a new discovery! Magnetic fields play an important role in the production of stars, planets and life, and the measurement of interstellar magnetic field strength in molecular clouds is a common challenge in the global astronomical community. Using FAST, an international collaboration team led by Qing Daochong and Li Jing of the National Astronomical Observatory of the Chinese Academy of Sciences found that, unlike the Standard Model prediction, the interstellar medium has a coherent magnetic field structure from cold neutral gas to protostar nuclei.
This is a breakthrough in the use of atomic radiation to detect the magnetic field of molecular clouds "from 0 to 1", and provides important observational evidence for solving the "magnetic flux problem", one of the three classical problems of star formation. The result paper was officially published in the form of a cover article in the international academic journal Nature on January 6, 2022, Beijing time.
Since passing the national acceptance on January 11, 2020, FAST's annual observation time has exceeded 5300 hours, far exceeding the work efficiency expected by international peers.
【Potential to solve major astrophysical problems】
Neutral hydrogen is the most abundant element in the universe and is widespread at different times in the universe. Li's team developed and named the original neutral hydrogen narrow line self-absorption method, which obtained for the first time the highly reliable "Zeyman effect" (atomic spectrum splitting under the applied magnetic field) measurements in the protostar nuclear envelope.
"FAST has unparalleled sensitivity and excellent optical path design, and it detects a magnetic field strength of only one hundred thousandth of the Earth's magnetic field, which is at least 3-4 times weaker than the magnetic field strength predicted by the Standard Model of Star Formation." According to researcher Li, this result reveals that there may be a more efficient magnetic field dissipation mechanism than the Standard Model, making star formation occur ahead of schedule. This achievement is expected to expand the neutral hydrogen narrow line self-absorption method into an important systematic probe for interstellar magnetic field measurement.
The result paper was published in Nature as a cover article
Richard Kruchel, a well-known scientist in the field of international interstellar magnetic field measurement and professor at the University of Illinois in the United States, commented that FAST has revealed for the first time that in the early stages of star formation, magnetic pressure is not enough to prevent gravitational contraction, which is crucial for understanding the astrophysical process of star formation and shows the potential of FAST in solving major astrophysical problems.
【Obtain the largest sample of fast radio burst events to date】
Fast radio bursts, the brightest radio bursts that last just a few milliseconds, have one of the biggest mysteries in astrophysics over the past decade or so.
Hundreds of rapid radio bursts have been detected, and only a few of them have shown repeated outbreaks. FRB121102 is the first repeating burst known to mankind, and in 2017 it became the first rapid radio burst to be precisely located to confirm its host galaxy, a result that the American Astronomical Society has called "the most significant discovery in astronomy since LIGO gravitational wave detection."
From August to October 2019, an international cooperation team led by Li Jing, Wang Pei and Zhu Weiwei of the National Astronomical Observatory used FAST to successfully capture the extreme activity period of this fast radio burst, with the most violent period reaching 122 outbreaks per hour. The researchers detected 1652 bursts in about 50 days and obtained the largest sample of rapid radio burst events to date, exceeding the total number of outbreak events previously published in all previous articles in the field, and becoming a milestone in the systematic study of repeated bursts of fast radio bursts. They revealed for the first time the complete energy spectrum of fast radio bursts and their bimodal structure, and the paper was published in Nature on October 14, 2021.
The FAST Multiscience Target Survey has discovered at least six new fast radio bursts and is making a unique contribution to revealing the mechanisms of mysterious phenomena in this universe and advancing this entirely new field of astronomy.
[Discovery of pulsars is one of the main scientific goals]
Pulsars are the "remains" of massive stars after their death, with a sugar cube-sized volume of hundreds of millions of tons of mass, and pulsars can emit highly periodic pulses with periods ranging from 1.4 milliseconds to 23 seconds. Known as the "millisecond pulsar," the short-period pulsar rivals the best atomic clocks on Earth. Therefore, the discovery of pulsars is one of the main scientific targets for observation by large international radio telescopes.
FAST is currently the highest precision timing device for pulsars, and its timing accuracy is 5-40 times higher than that of the international pulsar time measurement array IPTA. "What we used to do was second-hand material, but now it's time for Chinese to contribute to the frontiers of science." In less than two years, the "Silver Road Surface Pulsar Snapshot Survey" team led by Han Jinlin of the National Astronomical Observatory has discovered 279 new pulsars, of which 65 are millisecond pulsars and 22 are in the binary star system. The number of pulsars discovered in the year and a half of the work has surpassed the results of a 15-year search by the Arecibo Telescope in the United States. "We plan to look at the Galaxy in 8 to 10 years and look forward to more original discoveries."
Combining FAST with the high-energy band Fermi Gamma-ray Observatory's Large Field of View Telescope for space-earth integration coordination and follow-up observations has the potential to produce major scientific breakthroughs. The international cooperation team led by Li Jing and Wang Pei of the National Astronomical Observatory discovered a number of pulsars through this multi-band cooperative observation. Multi-band cooperative observation not only opens up a new direction for FAST pulsar search, but also opens up a new way to study the electromagnetic radiation mechanism of pulsars, providing more samples for the evolution of sub-star families and the detection of gravitational waves.