The Dawodang Depression in Pingtang County, Qiannan Buyi and Miao Autonomous Prefecture of Guizhou Province, is surrounded by mountains and green forests like the sea. The Five-hundred-meter Aperture Spherical Telescope (FAST), known as the "Chinese Sky Eye", is surrounded by mountains, like a giant eye on the earth, quietly gazing at the sky, searching for radio signals tens of billions of light-years away.
Since the opening of operation in China in January 2020, with the help of brand-new design ideas, unique location and breaking the limit of the 100-meter project of the astronomical telescope, the "China Sky Eye" has so far discovered more than 300 pulsars and is in rapid radio bursts. Major breakthroughs have been made in the research field. On March 31 this year, this major scientific research infrastructure with my country's independent intellectual property rights officially issued an invitation to astronomers all over the world to jointly salvage more "drift bottles" in the universe.
"Big eye" looking at the universe
Standing on the viewing platform and looking down, the large scientific device with a diameter of 500 meters built on the "tiankeng" in the Karst area looks like a silver "cauldron", which is erected on the surrounding 6 supporting towers with a height of more than 100 meters.
FAST chief scientist Li Di said that the device is currently the largest and most sensitive single-aperture radio telescope in the world. Its observation capability is 10 times that of the 100-meter telescope in Bonn, Germany, and 2.25 times that of the 300-meter telescope in Arecibo, the United States.
Just like the sailor pulling the cable to control the direction of the sail, FAST changes the direction of the antenna pan by pulling the wire rope net, which is controlled by more than 2,000 small motors connected to the wire rope net. The whole process of changing direction is calibrated by the laser positioning system. The suspended feeder cabin weighs 30 tons and is hoisted by six 400-meter-long steel cables with a moving range of up to 200 meters. The displacement of each part of the steel cable net and the feed cabin receiver must be controlled at the millimeter level, so that the large scientific devices can work normally.
When the wind is strong, people can hear the melodious "wind bells" from the entire FAST-that is the low-frequency sound produced by the vibration of its reflection unit. In the invisible underground, there are more than 100,000 optical fibers buried to provide guarantee for data transmission.
The birth of FAST can be traced back to the 1990s when astronomer Nan Rendong proposed to build China's own giant radio telescope. In 1994, the site selection work officially began. Nanren Dong and his team used more than 300 maps for 12 years to travel more than 1,000 depressions in southwest my country and finally selected Pingtang County, Guizhou Province, which has natural limestone topography, suitable size, and inaccessible to people. The scientific installations "settled down" here.
The construction process of the large scientific installation is arduous. Researchers and builders live in slab houses. There is no hot water or toilets indoors, and there are all dirt roads outdoors. Even if the road is paved, it will be crushed by heavy trucks passing by.
On September 19, 2016, the FAST system was successfully integrated and debugged. For the first time, the debugging team used the overall system to detect the first pulsar signal previously discovered by humans, which means that the device can operate normally. Li Di sighed, watching FAST step by step from an idea to a reality, it is really a miracle.
On August 27, 2017, the team achieved tracking and observation of a specific target for the first time, and stably obtained the radio signal of the target source, which means that the “eyeball”of FAST can be turned, and it also marks the most difficult and most risky telescope’s functional debugging is completed.
"After that, FAST can overcome the rotation of the earth and track the source of celestial objects. The sensitivity of the telescope is not only related to the receiving area, but also related to the tracking time. Just like the human eye, if you just glance at it, you can only look at it with rough outline. If you want to see the details, you need to look carefully at the target. This is also the most important function of the device." said Jiang Peng, FAST chief engineer and researcher at the National Astronomical Observatory of the Chinese Academy of Sciences.
Possessing super "discovery power" in many fields
On October 10, 2017, FAST announced the first astronomical discovery: a pulsar with a period of 1.9 seconds, 16,000 light-years away from the earth. " That day was the most memorable day in my life, as if a child who had been conceived for a long time was born." Li Di said.
In February 2018, a large scientific device detected the weakest millisecond pulsar in history. In fact, this pulsar has been "looked" many times by many astronomical telescopes on Earth but has not been "discovered", which fully proves the advantage of FAST in terms of sensitivity.
From the first discovery of a new pulsar to the announcement of the discovery of more than 100 pulsars at the end of the trial operation, to the breakthrough of 300 pulsars in one fell swoop....The number of pulsar discovered by FAST is second to none in the ranks of the global pulsar search team, becoming the important contributor of pulsar discovery.
In January 2021, the team made new discoveries, using 2018 data to find 4 new fast radio bursts. "Assuming that the universe was born during the Big Bang, so far, it can be divided into four stages: childhood, adolescence, youth, and middle age. The four fast radio bursts discovered by FAST this time are all in the teenage years of the universe, which makes us explore The origin of the universe has gone a step further." Li Di said.
Becoming a "world stage" for exploring the universe
At 0:00 on March 31, 2021 Beijing time, FAST issued an invitation to astronomers around the world to invite applications for observations. All foreign application projects will participate in the review. The review results will be announced on July 20 this year, and the observation time will start in August.
The relevant person in charge of the National Astronomical Observatory of the Chinese Academy of Sciences said that FAST is fully open to the world and demonstrates the concept of full cooperation between China and the international scientific community. In open cooperation, China's scientific structure will perform better, promote the output of major achievements, and contribute to the exploration and understanding of the universe for all mankind.
After years of construction and development, FAST has grown from nothing to gradually growing into a "world stage" for scientists to explore the universe.
"Before the establishment of FAST, there was no large astronomical telescope in the world that could simultaneously observe the imaging of atomic hydrogen and the search of pulsars." Using a large scientific device, Li Di and his team designed multiple scientific objectives to survey the sky at the same time, realizing it in one observation with gas imaging, search for gas galaxies, capture pulsars and fast radio bursts. The team expects to obtain 1,000 new pulsars, 500,000 new galaxies, 10 billion neutral stars with 3D pixels, and 50 new fast radio bursts. "Simultaneous surveys of multiple scientific targets will greatly improve the efficiency of our scientific output."
"Mr Nan Rendong once said that FAST not only represents the ambitions of scientists in the field of radio astronomy, but also an effort in China's astrophysics and astronomy science from catching up to surpassing." Li said that in the next two years, FAST will commit to discovering the farthest pulsar known to mankind, it will participate in the detection of low-frequency gravitational waves, and gradually reveal the composition of the gas and galaxies in the universe. Around its own scientific goals, FAST's attempts have just begun. "Curiosity is the pleasure of scientists, and it is also necessary for human survival. Constantly exploring the unknown mysteries of the universe will achieve more results that we can't even imagine."
