Zero-distance
"China Sky Eye" 4-year welcome achievement blowout
So far, more than 240 pulsars have been discovered, and more than 40 high-level papers have been produced
Mysterious and unknown things always seem to have a kind of magic power, attracting human beings to continue on the road of exploration.
Astronomy is like this: in the vast universe, there is often a wave of electric waves that only flashes for a few milliseconds.
No one knows what it is.
In 2007, astronomers found such millisecond radio waves in the signals recorded by Australia's 64-meter radio telescope in 2001.
Subsequently, astronomers have been trying to find the truth: who sent the radio waves?
What information does such a fast flashing electric wave contain?
After about 10 years of exploration, astronomers have collected more than 30 burst sources, which are almost randomly distributed in space, so they concluded that "the vast majority of these millisecond electric wave flash sources are not emitted by celestial bodies in the Milky Way."
In 2017, international astronomers finally captured a millisecond radio burst and used multiple large radio telescopes around the world to jointly detect and locate the rapid radio flash source of this repeated burst to a galaxy 3 billion light-years away in the depths of the universe.
In those years, China did not have much say in this frontier field.
Because China does not have sufficiently large radio telescopes, it is difficult for Chinese astronomers to obtain first-hand information, so most of them do theoretical research.
In 2016, the FAST (500-meter-caliber spherical radio telescope), known as the "China Sky Eye", was completed. Its reflecting surface is equivalent to 30 football fields. After 3 years of debugging, it has become the world's most sensitive radio telescope without any dispute. Expanding the horizons of mankind also gives Chinese astronomers finally the opportunity to be at the forefront of the human horizon.
Today, the FAST telescope has been opened to domestic astronomers, and original breakthroughs have emerged one after another.
Remember the scientific question of "Who sent the millisecond wave?"
The FAST telescope gave the latest observations, and Chinese astronomers revealed the new physics of the cosmic millisecond radio burst. The related achievements and papers appeared in the international academic journal "Nature" twice.
"A final word" for the two major battles
The story starts from a year ago.
According to Li Kejia, a professor at Peking University and a researcher at the National Astronomical Observatory of the Chinese Academy of Sciences, the research team hoped to use the FAST telescope to observe an explosion source FRB 180301 detected on March 1, 2018 in Australia during the trial open observation of the FAST telescope in 2019. , To see if this source will repeatedly erupt.
Fortunately, on July 16, 2019, a 2-hour FAST telescope observation detected 4 outbreaks as expected.
"This result is exciting!" said Han Jinlin, a researcher at the National Astronomical Observatory of the Chinese Academy of Sciences.
However, during the four hours of observation on September 11, the research team did not detect any signals.
After internal research by the research team, it was discovered that the original location of the explosion source reported by Australia existed, and then the observation strategy was adjusted, the telescope was aligned to the new location, and the polarization signal was recorded.
Soon, the effect of the strategy adjustment became apparent.
On October 6 and 7, 2019, the FAST telescope detected 11 eruptions within 6 hours.
According to statistics, in a total of 12 hours of observation time, the FAST telescope detected 15 flashes, and the intensity curve of each flash is different.
"This source of the outbreak is similar to the source of the outbreak 3 billion light-years away, and the rate of radio bursts is similar, but the intensity is much weaker." said Luo Rui, a Ph.D. jointly trained by Peking University and the National Astronomical Observatory of the Chinese Academy of Sciences.
The more gratifying result comes from the analysis of the highly sensitive polarization signal of 11 bursts.
Jiang Jinchen, a Ph.D. co-trained by Peking University and the National Astronomical Observatory of the Chinese Academy of Sciences, said that among the 11 burst signals observed by the FAST telescope, 7 milliseconds flashed out, which can well resolve their polarization.
What is exciting is that these 7 polarizations are not only changing, but also showing a variety of changes.
Such a changed polarization has never been seen in previous repeated explosions.
"These also show once again that the polarization measurement capability of the receiver equipped with the FAST telescope is very good." Li Kejia said.
In the past, telescopes in the world only recorded polarization signals for "a few of more than 30 burst sources," and very few samples could be studied in detail.
Previous detections have shown that the source of repeated bursts either exhibits a flat polarization angle, that is, the polarization plane of the radio wave remains unchanged; or it is a phenomenon of polarization angle changes, which have only been seen twice in a single burst source.
Today, the diversity of polarization changes observed by the FAST telescope clearly shows that the source of explosions in the universe may come from physical processes in the magnetosphere of compact stars.
This observation has directly challenged a group of international scholars' theory that the explosion comes from particle collisions, and has given a final word to the theories of the two martial arts in recent years.
This research paper was published in the journal Nature in the early morning of October 29, 2020 Beijing time.
Unveiling the new physics of millisecond radio bursts in the universe
In April 2020, FAST telescope ushered in a new user-Lin Lin, a lecturer at Beijing Normal University.
She is also the first author of another recent "Nature" paper by FAST Telescope.
Lin Lin and her team have submitted an application for observation of the source of repeated soft gamma-ray bursts of the Milky Way magnetar SGR J1935+2154.
The FAST telescope continuously monitors this.
However, during the active period of the X and soft gamma-ray bursts of the magnetar, especially the precise time nodes corresponding to the 29 soft gamma-ray bursts, the FAST telescope did not detect any source radio radiation.
"This shows to a certain extent that the physical conditions for the explosion of compact celestial bodies in different bands in the universe are very harsh, and radio and gamma photons cannot sweep the earth at the same time." According to Wang Pei, a member of the joint research team and an assistant researcher at the National Astronomical Observatory of the Chinese Academy of Sciences, The FAST telescope combined with previous detections gave this fast radio burst source the most stringent radio current limit so far.
The so-called fast radio bursts are the brightest explosions in the radio band in the known universe. They last for a very short time, usually only a few milliseconds, and emit a huge amount of energy. So far, there is no clear explanation of its origin.
Wang Pei said that the key to this field is to certify its counterparts.
Magnetars are highly magnetized special neutron stars. On April 28, 2020, the Canadian Hydrogen Intensity Mapping Experimental Telescope detected the millisecond-level radio pulse burst FRB 200428 for the first time in the Milky Way Galaxy SGR J1935+2154, and tracked the magnetar. The connection with fast radio bursts.
Today, FAST telescope observations are combined with international multi-band equipment, and the results show that FRB and SGR outbreaks have a weak correlation.
"The measurement results of the FAST telescope have played an important role in the study of the origin and physical mechanism of fast radio bursts." Wang Pei said.
This research result was published online in the journal Nature in the early morning of November 5th, Beijing time.
"Climbing on the road of'big results'"
With a series of breakthroughs in key technologies, the FAST telescope passed the national acceptance on January 11, 2020, marking that all technical indicators of the telescope have reached the design requirements and are already in place for open operation.
Jiang Peng, the executive deputy director and chief engineer of the FAST Operation and Development Center, said that at present, the FAST telescope facilities are operating stably and reliably, and more than 5,200 observation hours have been observed and served in the past year.
When talking about this stable observation data, Jiang Peng specifically mentioned the contribution of the local government: “Guizhou Provincial Party Committee and Provincial Government has made a very big sacrifice in the field of telescope electromagnetic environmental protection.” He said that the local government’s matching funds have solved the problem. For FAST telescope's dual-circuit power supply, ground disaster management and other issues, more than 20 anti-hail stations have been set up around it, making silent contributions to the safe operation of the telescope.
In February 2020, FAST officially launched 5 priority and major projects selected by the scientific committee. Nearly 200 scientific users have begun to use and process FAST scientific data.
In April, the FAST Time Allocation Committee began to solicit free application projects from the domestic astronomy community.
"We have received more than 170 applications. The total application time is about 5,500 hours. The actual approval of 1,500 machine hours-only nearly 30% can be supported. This shows that the FAST telescope observation time competition is quite fierce." Jiang Peng said.
Wu Xiangping, academician of the Chinese Academy of Sciences and director of the FAST Scientific Committee, said that with the improvement of performance, the scientific potential of FAST is gradually emerging.
In his view, FAST has the strongest absolute sensitivity in history, making it a great potential for radio transient sources.
Up to now, more than 240 pulsars have been discovered based on FAST data, the number one in the world at the same time, and more than 40 high-level academic papers have been published——
In April this year, researchers from the National Astronomical Observatory of the Chinese Academy of Sciences used FAST observation data to discover a typical "redback spider" pulsing binary star system M92A in the globular cluster M92, which is about 26,000 light-years away from the earth. This is also the first detection in M92. Pulsars arriving.
The discovery was also selected as a highlight research result by the American Astronomical Society.
In May, researchers from the National Astronomical Observatory of the Chinese Academy of Sciences Zhu Weiwei, Li Dan, and their collaborators used self-developed search technology, combined with deep learning artificial intelligence, to conduct a fast search on FAST's massive sky survey data, and discovered a new fast radio burst for the first time.
In July, the Chinese Academy of Sciences South American Astronomical Center Cheng Cheng and other researchers used FAST's 19-beam receiver to conduct pilot observations of 4 galaxies in a batch of low-redshift star-forming galaxies, and detected the neutral hydrogen emission of 3 galaxies for the first time. line.
In February 2016, after the LIGO cooperation group announced the first direct detection of gravitational waves predicted by general relativity for a long time, the detection of gravitational waves has become a hot topic in astronomy.
Wu Xiangping said that through long-term monitoring of millisecond pulsars, a certain number of millisecond pulsars are selected to form a timing array, which can detect low-frequency gravitational waves from supermassive double black holes and other celestial bodies.
"Thanks to the super-high sensitivity of FAST, we have increased the pulsar's timing accuracy by at least an order of magnitude, which is expected to give mankind the ability to detect gravitational waves in the NHz range for the first time." Wu Xiangping said, "It can be said that we are already on the road. "Great Results' on the road of climbing."
He also said that the current results only prove the height that the scientific output of the FAST telescope can reach, "but this should not be the end, but a new starting point."
China Youth Daily · China Youth Daily reporter Qiu Chenhui Source: China Youth Daily