The Big Bang of Science
"Chasing Stars" with China Sky Eye
The post-90s boy Niu Chenhui was "shocked" by the starry sky.
At that time, he was in Xinjiang. Because of his interest in astronomical instruments, he took the initiative to invite Ying to join the key technology experiment project of dark energy radio detection at the National Astronomical Observatory of the Chinese Academy of Sciences.
It was the Teana experimental array composed of 3 sets of parabolic cylindrical radio telescopes and 16 dish radio telescopes, which was built in 2014.
The location of the observatory is high above sea level and the air is dry. The "thick disk" of the Milky Way hangs in the sky, and it seems to be close at hand.
Niu Chenhui took the star map and searched for familiar or unfamiliar constellations with his companions.
He told a reporter from China Youth Daily and China Youth Daily: "The stars I saw in that place were really beautiful. Since then, my feelings about the stars have changed, and I have become interested in astronomy."
The shock of "seeing the stars" prompted the young man born in the 90s to come to China Sky Eye (FAST) deep in the mountains of the southwest to continue "chasing the stars": after graduating as a doctoral student in 2019, Niu Chenhui chose to join the National Astronomical Observatory of the Chinese Academy of Sciences for radio astronomy research In the Department of Interstellar Medium Evolution and Star Formation, researcher Li Di, the chief scientist of China Sky Eye, is the leader of the discipline, and has studied "fast radio bursts".
Most of the team members were seniors and teachers of Niu Chenhui, who were about the same age as him, including assistant researcher Wang Pei who was a few years older than him, and two doctoral students Feng Yi and Zhang Yongkun who were studying at the time.
On January 11, 2020, China Sky Eye was officially opened for operation. According to Li Di's previous speech, "China has the most advanced equipment in the world in the radio band".
From the perspective of astronomical research, the young people behind the "eyes of the sky" such as Niu Chenhui and Zhang Yongkun have caught up with a good era.
"China Tianyan is built for the next generation, for younger scientists and latecomers"
Zhang Yongkun is the youngest in the entire team.
In 2019, after graduating from the University of Chinese Academy of Sciences, he went straight to a Ph.D., with Li Di as his mentor.
Zhang Yongkun's undergraduate major is physics, and he often goes to the National Astronomical Observatory to listen to lectures.
When he was writing his graduation thesis, it was just in time for the completion of the construction of China Tianyan.
"I am very interested in such a big telescope project in our country and want to participate." Zhang Yongkun said.
So he sent Li Di an e-mail of self-recommendation.
When he went to the National Astronomical Observatory for an "interview", Zhang Yongkun specially printed out his transcripts and wanted to show them to Mr. Li.
Li Di said no, and then discussed the topic of his graduation thesis with him, and told him what the Chinese Sky Eye could do.
Since then, Zhang Yongkun has been exposed to fast radio bursts (Fast Radio Burst, FRB for short), "this is a promising field for our young people".
A fast radio burst is a mysterious explosion phenomenon in the universe, which refers to a violent explosion of energy that takes about a year from the sun to radiate in milliseconds.
In 2007, the first detected FRB was announced.
But the origin and physical mechanism of this mysterious phenomenon is still unknown.
Due to the update of observation equipment and the application of new technologies, the number of FRBs has increased from the early single digits to nearly 500 cases in the following 10 years.
The FRBs discovered earlier have only detected one burst, which is considered to be "unrepeatable".
Until 2016, a class of fast radio bursts that can burst multiple times was repeatedly detected, and the inherent cognition was broken.
As the world's largest single-aperture radio telescope, FAST has been searching for fast radio bursts a few years ago.
Not long ago, Li Di's team discovered the only persistently active repeating fast radio storm FRB20190520B so far through FAST's "Multi-Scientific Target Simultaneous Sky Survey" priority major project.
On June 9, 2022, Beijing time, the result was published in the international academic journal "Nature", and Niu Chenhui was the first author of this paper.
"This observational discovery has very important scientific significance for understanding the surrounding environment and physical origin of FRBs. Since its discovery in 2007, FRBs have been one of the most cutting-edge research directions in the field of astronomy, especially their physical origins. , radiation mechanism and the surrounding environment are three of the key scientific issues to be solved urgently." Dai Zigao, professor of astrophysics at the University of Science and Technology of China, said at the release of the results.
China Sky Eye has been in operation for more than two years, and the data it has acquired has spawned more than 100 academic papers.
In 1996, the older generation of radio astronomers from the National Astronomical Observatory, Mr. Nan Rendong and Mr. Qiu Yuhai, went to the Arecibo Telescope in Puerto Rico to investigate this huge radio telescope.
According to the foreseeable development prospects of modern technology at that time, combined with my country's strengths and weaknesses in engineering, the concept of China's sky eye has become more and more three-dimensional in the minds of these two old astronomers.
At the end of 2007, the National Development and Reform Commission approved the project proposal for a 500-meter-aperture spherical radio telescope.
Li Di once recalled in his speech his experience when he participated in the construction of China's Sky Eye, which was "very different" from the work of astronomical observers he had seen before.
These "Sky Eye" builders moved bricks, planted trees, and spliced optical fibers in the mountainous areas of Guizhou... The main engineering team has lived in prefabricated houses for more than 6 years, and there is no hot water or toilet indoors.
Even though it was so hard, all were still "in very good spirits".
"The hardest road has been smoothed by the seniors." Niu Chenhui sighed.
Nan Rendong often said, "FAST is built for the next generation, for younger scientists and latecomers".
In Li Di's view, China Sky Eye represents "an attempt from catching up to surpassing" in Chinese radio astronomy.
"I feel lucky to be able to stand on the shoulders of giants," said Niu Chenhui.
From nearly 1,000 hours of data, find 4 "blinks"
So far, China Sky Eye has discovered 6 FRBs, 4 of which were discovered by Niu Chenhui.
Hearing others mention this, he would bow his head and smile, explaining that he was just lucky, just in time for the stage when the Chinese Heavenly Eye began to bear fruit.
This so-called "luck" is inseparable from hard work and rigor.
The electromagnetic wave signal from the universe was received by a spherical "cauldron" with a diameter of 500 meters and presented to the researchers in the form of a digital matrix.
According to Zhang Yongkun's description, China Sky Eye can observe 19 points in the sky at the same time. After operation, the data received by each point per hour is about 2TB.
"Our main job is to process the data observed by FAST." Zhang Yongkun told a reporter from China Youth Daily and China Youth Daily, "FAST has about 5,000 operating hours a year, and it is estimated that there may be dozens of them a year. Data on the scale of petabytes. Our team’s project has about a thousand hours of data to process a year.”
Most of the data, in fact, is noisy "noise" from molecular gas dispersed in the universe, radio signals from various celestial bodies, and electromagnetic waves from the ground.
The fast radio bursts the researchers are looking for are a "blink" of only a few milliseconds superimposed on these noise backgrounds.
Niu Chenhui found 4 "blinks" from nearly 1,000 hours of data.
In the process of systematically processing China Sky Eye data, Niu Chenhui found that the data on May 20, 2019 had repeated high-dispersion pulses.
After ruling out pulsars and radio interference, the researchers determined that the pulse came from a new fast radio burst, which they named FRB20190520B.
Based on this discovery, Li Di's team, in cooperation with the Very Large Array Telescope in the United States, completed precise positioning in July 2020 and detected a dense continuous radio source.
Since then, the researchers have determined the host galaxy and redshift of FRB20190520B using the Palomar 200-inch telescope and the Keck telescope in the United States, the Canada-France-Hawaii telescope and the Subaru near-infrared optical telescope in Japan.
After further combining the scattering features, the research team found that FRB20190520B does not have a window period like other FRBs, but is continuously active.
"This result reports a new fast radio burst that challenges our understanding of the host galaxy of these mysterious phenomena. FRB20190520B was first discovered by China's FAST telescope and subsequently showed that it repeats on average every 10-15 minutes." Duncan Lorimer, a professor at the University of Virginia and the discoverer of fast radio bursts, commented on the results.
Play ball and sing together, sit on the "cold bench" and do scientific research together
"There will always be surprising new discoveries, and we never know what subversive phenomena are waiting ahead," said Feng Yi, another student of Li Di.
In March this year, Feng Yi’s paper as the first author was published in the international academic journal Science, pointing out that the repeated FRBs discovered by Niu Chenhui were in a complex environment similar to the remnants of supernovae.
Constantly making new discoveries is a wonderful experience for Feng Yi.
He has been fascinated by physics since he was a child, and in the eyes of laymen, data screening work is extremely boring, but for this post-90s generation, it is just a waiting process.
"When FRBs were first discovered, astronomers once thought that FRBs were all outside the Milky Way, but suddenly a newly discovered FRB came out of a magnetar in the Milky Way. Everyone knew, oh, so there are also FRBs in the Milky Way. "Every time I talk about this, Feng Yi's voice is always filled with uncontrollable excitement.
After Niu Chenhui's latest results on fast radio storms were published in "Nature", Feng Yi forwarded his blessings on social platforms: a string of "soybean expressions" matched with heartfelt praise - "The era of Niu Superstars is coming!"
Niu Chenhui replied: "Feng Tianshi has to come up with more ideas."
"Superstar" and "Tianshi", these are the nicknames that the four young researchers in the team joke with each other.
Wang Pei, Feng Yi, and Zhang Yongkun are "Heavenly Masters", and the sky is the sky of the "heavenly eye", and it is also each other's expectations for the future.
Niu Chenhui's "superstar" title comes from the 70th anniversary of the founding of the Chinese Academy of Sciences.
At the anniversary event, the National Astronomical Observatory released a program. Niu Chenhui had just joined the team at that time, standing in the "C position" in the middle of the second row, and has since become a "superstar" in the mouths of his friends.
These young people play ball and sing together in the interval of scientific research.
They all grew up listening to Jay Chou and Mayday's songs, and they all yearn for science and love science, and are willing to sit on the "cold bench" to engage in basic research.
A question that Niu Chenhui often hears is, what is the use of studying astronomy and studying fast radio bursts 3 billion light-years away?
He didn't know how to answer these questions.
He always feels that his research is "very interesting", and the exploration itself is the meaning.
China Youth Daily, China Youth Daily reporter Zhang Miao Source: China Youth Daily