It has been nearly two years since China Sky Eye (FAST) passed the national acceptance on January 11, 2020. In the past two years, in accordance with the requirements of "high-level management and operation of this major scientific infrastructure, early results, more results, good results, and great results", the National Astronomical Observatories of the Chinese Academy of Sciences has set up a FAST scientific committee, a time allocation committee and a user committee for the first time while fully organizing the high-quality open operation of FAST, to plan the scientific direction, select major projects, formulate data open policies, and allocate observation time. In order to give full play to the scientific effectiveness of FAST and promote the output of major scientific achievements, the Scientific Committee has collected and selected five priority major projects around the scientific goals of FAST advantages, organized outstanding scientific research teams across the country, and carried out large teams to focus on key problems, and achieved a series of important results.
Figure 1. China Sky Eye FAST
On March 31, 2021, FAST officially opened its shares to the world and solicited observation applications from astronomers around the world, highlighting the concept of Chinese scientists working together with the international scientific community. The call for a total of 7216 hours of observation applications was received from different countries, and 27 international projects from 14 countries (excluding China) were approved, and scientific observations were launched in August 2021.
Fast's operational efficiency and quality have been continuously improved, and the annual observation time has exceeded 5300 hours, which has far exceeded the work efficiency expected by international peers, and has played an important supporting role for FAST scientific output. To date, FAST has discovered about 500 pulsars, making it the most efficient device in the world since its operation.
Figure 2. China's sky eye multi-scientific target simultaneously scans the sky survey art map
(Copyright: National Astronomical Observatory)
In 2021, a number of important scientific research achievements have been achieved relying on FAST.
FAST neutral hydrogen spectroscopy has made significant progress in measuring interstellar magnetic fields. Neutral hydrogen is the most abundant element in the universe, widely present at different times in the universe, and is one of the best tracers for the distribution of matter at different scales. The international cooperation team led by Qing Daochong and Li Jing of the National Astronomical Observatory used the original neutral hydrogen narrow line self-absorption method to obtain the high confidence Seyman effect measurements in the protostar nuclear envelope for the first time using FAST. The discovery of a coherent magnetic field structure in the interstellar medium from cold neutral gas to protostar nuclei is different from the prediction of the Standard Model, providing important observational evidence for solving the "magnetic flux problem", one of the three classical problems of star formation. -The paper was officially published as a cover article in the international academic journal Nature on January 6, 2022, Beijing time.
Figure 3: The cover design of the journal Nature, showing the interstellar medium and magnetic field in the molecular cloudy area of Taurus. The curve is a magnetic field direction map measured by the Planck satellite, and the background nebula is from a dust image taken by the Herschel Space Telescope.
The largest rapid radio burst event sample to date was obtained, revealing for the first time the complete energy spectrum of fast radio burst and its bimodal structure. Fast radio bursts (FRBs) are the brightest radio bursts in the universe, with unknown origins, and are the latest hotspots in astronomy. The international cooperation team led by Li Yong, Wang Pei and Zhu Weiwei of the National Astronomical Observatory used FAST to observe FRB121102, detected 1652 burst events in about 50 days, obtained the largest sample of fast radio burst event to date, exceeded the total number of outbreak events published in all previous articles in this field, and revealed for the first time the complete energy spectrum of fast radio bursts and their bimodal structure, and the result paper was published in the international academic journal Nature on October 14, 2021. The FAST Multiscience Goal Survey has discovered at least six new FRBs and is making a unique contribution to revealing the mechanisms of mysterious phenomena in the universe and advancing this entirely new field of astronomy.
Figure 4. (left panel) Energy distribution of fast radio burst FRB 121102 average hourly burst rate. At the low energy end of 90% detection completeness, the explosive rate below the characteristic energy E0=4.8x1037erg began to decline, showing a complex energy distribution. (Right) FAST observation of fast radio burst art image, the pulse from fast observation FRB 121102 real data.
The "Silver Road Surface Pulsar Snapshot Survey" project continues to discover millisecond pulsars. The discovery of pulsars is one of the main scientific targets of observations by large international radio telescopes. In less than two years, the FAST major priority project "Silver Road Surface Pulsar Snapshot Survey" led by Han Jinlin of the National Astronomical Observatory has completed the planned search for 8% of the planned sky area in about 620 machine hours, and so far the project has discovered 279 new pulsars, of which 65 are millisecond pulsars, and 22 are in the binary star system. The relevant paper was published in the domestic academic journal "Astronomy and Astrophysics Research" in May 2021. Professor Manchester, an internationally renowned scholar and academician of the Australian Academy of Sciences, commented that "the discovery of so many pulsars is impressive" and "the discovery of so many millisecond pulsars is a remarkable achievement". 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.
Carry out multi-band cooperative observations, open up new directions for pulsar search, and open up new ways to study the electromagnetic radiation mechanism of pulsars. Based on the international leading advantage of FAST sensitivity, the combination of FAST and the Fermi Gamma-ray Observatory's Large Field Telescope (Fermi-LAT), an important space astronomical facility in the high-energy band, for space-space 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 and carried out multi-band observation and analysis. The relevant results were published in the form of cover and editorial comments in the domestic academic journal "Science in China" in December 2021. 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.
Figure 5. (Left) PSR J0318+0253 position and integration pulse profile. a) FAST tracks the radio band integration profile of the observed one-hour track; b) gamma photon integral pulse profile obtained by folding Fermi-LAT's accumulated 9 years of data. (Right) FAST-FermiLAT collaborates on pulsar observational art visualization, cover of Science in China, No. 12, 2021.
Based on the obvious advantages of ultra-high sensitivity, FAST has become a sharp tool in the field of medium and low frequency radio astronomy, and will produce scientific achievements to deepen human understanding of the universe in the direction of the origin and physical mechanism of fast radio bursts, neutral hydrogen universe research, pulsar search and physical research, pulsar timing and low-frequency gravitational wave detection.
On February 5, 2021, when General Secretary Xi Jinping inspected Guizhou, he listened to the FAST work report and video connected to comfort the on-site staff. General Secretary Xi Jinping pointed out that China's heavenly eye is a giant eye for viewing the sky and a heavy instrument for the country, and has achieved a major original breakthrough in the field of cutting-edge science in China. The general secretary's cordial concern for the Chinese Academy of Sciences and the vast number of scientific and technological workers reflects the ardent expectations for scientific and technological self-reliance and self-reliance and strengthening of the national strategic scientific and technological strength. The Chinese Academy of Sciences will share scientific research facilities with the world in a more open manner, provide a high-level observation platform for the international astronomical community, promote international cooperation in astronomical research, enhance the international status and influence of Astronomical research in China, and contribute "Chinese wisdom" to the construction of a community with a shared future for mankind with "Chinese wisdom" to promote the development of world science and technology and the progress of human civilization.
National Astronomical Journal of China, December 2021
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