The origin of fast radio bursts was revealed, more than 240 pulsars were discovered, and FAST officially operated for 300 days——

Explore the vast interstellar power

　　Our reporter Wu Yuehui

　　"People's Daily" (12th edition on November 06, 2020)

　　Core reading

　　Since its official operation for 300 days, the 500-meter spherical radio telescope (FAST) known as the "China Sky Eye" has discovered more than 240 pulsars.

With the help of FAST, the Chinese scientific research team has quickly become the core research force in the field of international rapid radio storms.

　　In the vast universe, short and violent radio wave bursts often appear suddenly, lasting only a few milliseconds, but they can release the energy released by the sun throughout the day. This is called a rapid radio burst.

What information does such a fast flashing radio wave contain?

Astronomers from various countries have been seeking the truth.

　　Recently, with the help of the latest observations from the 500-meter spherical radio telescope (FAST) known as the "China Sky Eye", Chinese scientists have achieved a series of major achievements in the study of fast radio bursts.

On October 29 and November 4, two related research results were published in the journal Nature, making the "Chinese Sky Eye" once again the focus of the radio astronomy community.

　　Strong support for high-level research

　　How do rapid radio storms occur?

Previous theoretical studies are mainly divided into two types. One is that such millisecond radio bursts are caused by particle collisions, and the other is that they are generated by particles traveling through a strong magnetic field.

　　"FAST observations directly ended the debate. Through the analysis of the highly sensitive polarization signals of 11 radio bursts, Chinese researchers rejected the theory of particle collisions with direct observations." said Han Jinlin, chief researcher at the National Astronomical Observatory of the Chinese Academy of Sciences.

　　Relying on a series of “empirical evidence” of FAST observations, my country’s relevant scientific research teams have quickly become the core research force in the field of international rapid radio storms.

　　In 2019, Peking University professor and National Astronomical Observatory researcher Li Kejia's team used FAST to detect a repeated explosion of FRB180301 with only 21 cases in the world.

Li Kejia said: "In a total of 12 hours of observation time, FAST detected 15 flashes, and the intensity curve of each flash is different. The most wonderful result comes from the highly sensitive polarization signal of the 11 bursts. Resolve."

　　Li Kejia explained: “Of the 11 bursts observed by FAST, 7 millisecond bursts can be well resolved. The exciting thing is that the 7 polarizations are not only changing, but also showing changes. Diversity. Such changes in polarization have never been seen in previous repeated storms. The diversity of polarization changes observed by FAST clearly shows that the source of explosions in the universe may come from physical processes in the magnetosphere of compact stars."

　　In August this year, a joint research team including Dr. Lin Lin from Beijing Normal University, Dr. Chunfeng Zhang from Peking University, and Dr. Pei Wang from the National Astronomical Observatory used FAST to observe a known magnetar SRG1935+2154 in the Milky Way showing dozens of gamma-ray bursts. .

　　Lin Lin said: "With the high sensitivity of FAST, we did not detect a single radio burst in our radio waveband observations. This result shows that the physical conditions for the explosion of dense celestial bodies in the universe at different bands are very harsh, making radio and gamma photons You cannot sweep the earth at the same time."

　　Observation service exceeds 5200 machine hours

　　FAST was completed in 2016. Its reflective surface area is equivalent to about 30 standard football fields, which greatly expands the field of vision of human beings in the radio wave band, and finally gives Chinese radio astronomers the opportunity to be at the forefront of scientific exploration.

　　Since its official operation for 300 days, FAST has demonstrated amazing scientific strength.

FAST's observation service in the past year exceeded 5,200 machine hours, nearly twice the expected target, the cumulative number of pulsars discovered exceeded 240, and more than 40 high-level papers based on FAST data were published.

　　"In 1967, people discovered the first pulsar; until 50 years later, Chinese people discovered the first new pulsar with their own radio telescope FAST." said Wu Xiangping, director of the FAST science committee and academician of the Chinese Academy of Sciences. In a short period of time, FAST has discovered more than 240 pulsars, and we expect that this number will reach 1,000 in the next five years, and even the first radio pulsar outside the Milky Way can be found."

　　In February of this year, the FAST team officially launched 5 "priority and major projects" selected by the scientific committee. Nearly a hundred scientists began to use and process FAST scientific data; in April, the time allocation committee began to solicit free application projects from the domestic astronomical community. More than 170 applications have been received, and the proportion of external users is as high as 95.7%.

　　"Next year, FAST will be open to the whole world." Wu Xiangping believes that China will usher in the golden age of radio astronomy development in the next 10 years. "We must use this precious window period to make major scientific discoveries for mankind. Make a significant contribution to exploring and understanding the universe."

　　Scientific potential will be further revealed

　　The huge engineering volume, ultra-high-precision requirements and special working methods have posed unprecedented technical challenges for FAST. For this reason, the engineering team has carried out a series of technical research.

The construction of the FAST project has achieved a number of independent innovations, which has significantly promoted the innovation and development of related industrial technologies in my country.

　　"FAST's advanced measurement technology is far more than the telescope itself, and has important application prospects in other fields." said Jiang Peng, a researcher at the National Astronomical Observatory and chief engineer of FAST. "For example, in high-precision geological and mineral exploration, inertial components and satellites can be used. Navigation fusion technology provides high-precision position and azimuth attitude reference for gravity measurement; in marine surveying and mapping, inertial components are integrated with sonar and other measurement technologies to realize seabed surveying and mapping, and establish high-precision space-time and attitude for machinery and equipment operating in the exploration area Benchmark."

　　With the improvement of performance, the scientific potential of FAST will be further revealed.

Chang Jin, director of the National Astronomical Observatory and academician of the Chinese Academy of Sciences, said: "FAST's ultra-high sensitivity makes it a great potential for radio transient sources. It is expected to realize the detection of gravitational waves in the nanohertz in a short time and capture the original gravity of the Big Bang period. Wave provides data support for studying the physical process at the beginning of the Big Bang. At the same time, it also has the ability to extend my country's deep space exploration and communication capabilities to the edge of the solar system to meet major national strategic needs."