China's Sky Eye FAST found about 500 pulsars

The picture shows the flickering diagram of a fast radio storm in the FAST night sky (video screenshot). Courtesy of the National Astronomical Observatories of the Chinese Academy of Sciences

According to the People's Daily client news, the 500-meter aperture spherical radio telescope (FAST), known as the "China Sky Eye", has been officially accepted for nearly two years. The operation efficiency and quality of "China Tianyan" have been continuously improved, and the annual observation time has exceeded 5300 hours, which has far exceeded the work efficiency expected by international counterparts and played an important supporting role in its scientific output. On January 5, the Chinese Academy of Sciences released the news that in 2021, scientists have made a number of important scientific research achievements relying on the "Chinese Heavenly Eye".

Provides important observational evidence for solving one of the three classical problems of star formation

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 use the "Chinese Tianyan" to obtain the high-confidence Zeman effect measurement in the protostar nuclear envelope for the first time, which provided important observation evidence for solving the "magnetic flux problem", one of the three classic problems of star formation.

The paper was published in the form of a cover article in the international academic journal Nature on January 6, Beijing time.

"The magnetic field detected by China's Sky Eye is only one hundred thousandth of the Earth's magnetic field, which is at least 3-4 times weaker than the magnetic field predicted by the Standard Model of Star Formation." Li Jing, chief scientist and author of the china Tianyan Operation and Development Center, said, "This result reveals that molecular clouds can reach a magnetic supercritical state ahead of time at the dense cloud nucleus stage, and there may be a more efficient magnetic field dissipation mechanism than the Standard Model to make star formation occur ahead of schedule." This achievement is also expected to expand the neutral hydrogen narrow line self-absorption method into an important systematic probe for interstellar magnetic field measurement. ”

Significant progress has been made in revealing the underlying physical mechanisms of fast radio bursts

Fast radio bursts (FRBs) are the brightest radio bursts in the universe that last only a few milliseconds and were first discovered in 2007 as a supposedly pulse signal from extragalactic galaxies. At the beginning of the discovery, the academic community still had doubts about its authenticity, until more such phenomena were discovered in 2013, which gradually gained recognition and widespread attention, and was officially named fast radio burst. Because the origin and physical mechanism are completely unknown, it has become one of the biggest hot spots in the field of somatic physics today.

At present, hundreds of rapid radio bursts have been detected, and only a few of them have shown repeated outbreaks. FRB121102 is the first repeat burst known to mankind, and in 2017 became the first precisely located fast radio burst to confirm its host galaxy.

The international cooperation team led by Li Jing, Wang Pei and Zhu Weiwei of the National Astronomical Observatory used the "China Sky Eye" to observe FRB121102, detected 1652 outbreak events in about 50 days, and obtained the largest sample of rapid radio burst events to date, exceeding the total number of radio burst events published in all previous articles in this field.

After analyzing the samples, the researchers revealed for the first time the complete energy spectrum of the rapid radio burst burst rate, found the bimodal structure, ruled out the periodicity or quasi-periodicity of this fast radio burst burst, and strictly limited the possibility of repeatING FRBs from a single compact object. This is a major advance in revealing the basic physical mechanisms of fast radio bursts. The result paper was published in the international academic journal Nature on October 14, 2021.

In addition, the "China Sky Eye" multiscientific target sky survey has found at least 6 new fast radio bursts, which is making a unique contribution to revealing the mechanism of this phenomenon and promoting the development of this field.

Millisecond pulsars continue to be discovered and multi-band cooperative observations are carried out

Pulsars are capable of emitting 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. So far, the "China Sky Eye" has found about 500 pulsars, becoming the most efficient device in the world since its operation.

Equipped with a 19-beam L-band receiver, the "China Sky Eye" is currently the world's most powerful pulsar search weapon. The "China Sky Eye" major priority project "Silver Road Surface Pulsar Snapshot Survey" led by Han Jinlin of the National Astronomical Observatory has completed 8% of the planned search for the sky area in less than two years, accumulating about 620 machine observations. So far, the project alone has discovered 279 new pulsars, of which 65 are millisecond pulsars and 22 in binary systems. The work was carried out for 1 and a half years, and the number of pulsars found has surpassed the results of 15 years of searches by the Arecibo Telescope in the United States. The relevant paper was published in the domestic academic journal "Astronomy and Astrophysics Research" in May 2021.

Based on the international leading advantage of the sensitivity of "China Sky Eye", the combination of "China Sky Eye" and the large field telescope of the Fermi Gamma-ray Observatory, an important space astronomical facility, to carry out space-earth integration coordination and follow-up observation, 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.

Li Said: "Multi-band cooperative observation not only opens up a new direction for the search of 'China's Celestial Eye' pulsars, 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." ”

In the future, 1% of the observation time will be considered to be open to primary and secondary school students

Scientific and technological innovation is inseparable from international cooperation and open sharing. At the beginning of its construction, the "China Heavenly Eye" established the principle of gradual opening up in accordance with international practice. At 0:00 on March 31, 2021, "China Sky Eye" was officially opened to the world for sharing and solicited observation applications from astronomers around the world.

Zhou Qi, vice president of the Chinese Academy of Sciences, said: "In the past year, the Chinese Academy of Sciences has made every effort to do a good job in the open operation and scientific research of 'China's Sky Eye'. At the first time, the 'China Tianyan' Scientific Committee, Time Allocation Committee and User Committee were established to make overall planning of scientific directions, selection of major projects, formulation of data opening policies, etc., giving full play to the scientific effectiveness of 'China Tianyan' and promoting the output of major scientific achievements. ”

According to Jiang Peng, executive deputy director and chief engineer of the "China Sky Eye" Operation and Development Center, a total of 7216 hours of observation applications were received from different countries, and finally 27 international projects from 14 countries (excluding China) were approved, and scientific observations were launched in August 2021.

With the improvement of performance, the scientific potential of "China Sky Eye" will further emerge, and the results will continue to emerge. Wu Xiangping, an academician of the Chinese Academy of Sciences and a researcher at the National Astronomical Observatory, said: "In the future, FAST will also search for more pulsars, hoping to see more distant pulsars outside the Milky Way." At the same time, it continues to tour the neutral hydrogen in the universe and help scientists study the large-scale physics of the universe to explore the origin and evolution of the universe. ”

Wu Xiangping also revealed that "China Sky Eye" is considering taking 1% of the observation time to open up to primary and secondary school students across the country. "Primary and secondary school students can come up with good scientific ideas and professional astronomers can help them realize them."

Edited by Xin Jing