The mysteries of the universe have always been the hope that mankind is constantly exploring and helping to find a better future. On September 25, 2016, the cost was about 11The 500 million yuan "China Sky Eye" - a 500-meter aperture spherical radio telescope was officially completed.
The existence of this telescope not only provides tools for China's space exploration, but also opens the door for China's cooperation and sharing with the world in the field of astronomy.
In the face of such an important "China Sky Eye" that promotes people to explore the universe and costs nearly 400,000 yuan per day, people may wonder: what is the story of its construction?What exactly did it find after it started running?
fast is the English name of the telescope, and it also means "fast", but from the idea to the site selection, construction, and completion, the process seems to be somewhat "untouched" with the word "fast".
In 1994, Nan Rendong took the lead in proposing to build a new generation of radio "large telescopes" in China。However, in the following decade of site selection, it was discovered that it was so difficult to choose an ideal site.
Because the depression of the magnifying telescope is shaped like a "nest", it must also be naturally formed. These two seemingly simple conditions have made the scientific research team think hard.
In addition to the fact that there are fewer terrains that meet the requirements, in those years, the technical means of our country were very limited. Before 2002, although the scientific research team found some "nests", none of them met the requirements for placing FAST.
Therefore, in November of that year, when the research team of Guizhou University took over and started the second round of scientific research tasks for site selection, they had very little information to refer to. In this case, how should the follow-up work of the scientific research team be carried out?
The simplest and most feasible way the research team could think of was to look at the distribution characteristics of rocks one by one from a 1:500,000 topographic map.
In this process, the scientific research team first eliminated and determined the geographical location where the "nest" would not appear, and circled the locations that might be suitable.
Then, on a 1:10,000 topographic map, they "find circles" along dense contour lines at possible locations. If these circles are larger and more round, the more likely it is that the place will be a destination.
Around the "circle", the surrounding terrain is identified by numbers, whether it is a mountain peak or a depression.
Through this clumsy method, researchers have identified more than 10,000 potentially suitable depressions on more than 8,000 maps. Of course, Guizhou's "Dawotai" is also included.
But finding these depressions on the map is only a small step in the site selection process. After all, it is impossible for researchers to know which location is suitable with the naked eye, just by looking at the map. They used scientific means to select the most suitable location.
After identifying more than 10,000 possible sites, the research team screened 743 depressions that were most likely to be suitable and built a database of alternative sites. Subsequently, the team combined the literature to conduct a comprehensive analysis of the locations in the database.
It can be said thatThis analysis is very demanding. Because the scientific research team has to evaluate the local rock mass structure, hydrological conditions, depression closure, geometric shape, overall geological hazards in the region, meteorological conditions, radio environment and other indicators of different dimensions.
However, the hard work paid off. They finally selected 82 sites from the database to focus on. Some people may say that after such rigorous analysis and evaluation, why can't the scope of the investigation be narrowed down to single digits?
You should know that these terrains belong to the Koster Depression, and such terrain is mainly concentrated in many areas of Guizhou, and the natural depressions in these areas have a high degree of similarity, and it is difficult to select the best location from them based on data analysis alone.
In line with a cautious scientific research attitude, the team listed all the similarities of the sites as key objects. This spirit of "not giving up" is what real researchers need.
In this way, the team members began the work of the field trip.
Due to the traffic situation in Guizhou at that time, it was not satisfactory. When a team goes to a location, the time spent on the road alone can be as long as a day.
And, for the most part, they walk on a narrow mountain path with mountains on one side and cliffs on the other. In many cases, the off-road vehicle could not drive to the place to be inspected at all, and everyone could only carry the equipment, get out of the car and walk to the depression.
In addition, during the field trip, the team members have to do a lot of work, which is not what everyone imagined, and when they arrive at the site, they can simply look at the rocks, geology, and hydrology.
They also need to learn about the water system in the region. This is related to the question of whether it is safe to settle down after FAST.
You must know that if there is water in the mountain, there is no way to discharge it into the underground river, and FAST may face the fate of being flooded. If this happens, FAST is useless no matter how well it is built, and it simply cannot function as it should.
Therefore, everywhere the team goes, they find all the water sources there, whether it is the open river or the dark river, they will follow the river to study the process of hydrodynamics. What's more, the team often had to brave the scorching sun to find water.
At work, given that they are not locals, coupled with the requirements of confidential work, they do not dare to ask others for help at all, so they can only explore and find by themselves.
Thankfully,After several months of field investigation, the scientific research team designed and developed a set of three-dimensional site selection system based on the collected data, which greatly facilitated the development of the calculation work.
With the support of the system, through the analysis and calculation of the professional team, "Dawotai" finally appeared in front of people's eyes. The five calculation methods all show that its various conditions meet the needs of FAST, and it is the most suitable location for the construction of FAST.
After that,The scientific research team carried out more detailed research and calculations on the site, as well as the testing of various conditions and environments on the ground, and finally, the FAST project was officially selected in "Dawotai", Guizhou.
In addition to the difficulties in the process of site selection, China's various investments in construction and the training of scientific research teams are also huge. I won't go into them here. The point is to talk about what major discoveries it has made since it started operating
With the continuous advancement of science and technology, astronomy has increasingly relied on various types of telescopes for multi-messenger observations.
Each type of messenger, each band of electromagnetic waves, corresponds to different aspects of astrophysical processes, and the information transmitted to humans is different. Moreover, it is difficult for the various messengers to replace each other.
Radio is a band of electromagnetic waves. It is also called the radio band, which is the electromagnetic wave band with the lowest frequency and longest wavelength.
In order to better study radio electricity, radio astronomy began to rise, and radio telescopes also appeared, and their performance was continuously improved, which led to many important discoveries in radio astronomy.
Judging from the development trend of radio telescope sensitivity, the emergence of fast is also timely.
In fact, during the design phase, experts planned a series of scientific objectives for FAST, which are mainly divided into three parts: time domain, frequency domain and other scientific objectives.
Specifically, the science aspects of time domain include the search for pulsars and the timing of pulsar observations. In terms of frequency domain science, it is mainly to map the distribution of neutral hydrogen gas in the Milky Way and observe the neutral hydrogen and star molecules of extragalactic galaxies.
Other scientific objectives are participation in the Very Long Baseline Interferometry (VLBI) and the Search for Extraterrestrial Civilizations (SETI).
Later, as astronomy developed, experts also added some scientific goals to FAST. Among them, the most important is the observation of fast radio bursts (FRBs) in time domain science.
So after seven years of operation, what exactly did FAST find?
The first is about discoveries in time-domain science. The first thing it does is the observation of pulsars.
This is because pulsars are about the same mass as the Sun, but have a radius of only about 10 kilometers, and the object is very dense. Coupled with its strong gravitational pull, the star is able to rotate rapidly and periodically emit pulsed signals.
By observing pulsars, the research team can study particle generation and acceleration in the magnetosphereThe theory of relativity can be tested by measuring the pulse arrival time of pulsars in binary stars.
Pulsar timing array observations can also detect gravitational waves with frequencies on the nanohertz scale. If the research team can detect gravitational waves on the nanohertz scale, they may discover a binary star system consisting of pulsars and black holes.
It is precisely because of the existence of such an important target that the discovery of more pulsars has become a top priority.
By the end of July this year, it had discovered about 800 new pulsars, dwarf pulsed radiation and the shortest-period pulsar binary system to date, and detected key evidence of the existence of gravitational waves on the order of nanohertz.
While observing pulsars, FAST found a change in polarization in one FRB, suggesting that at least part of the FRB is associated with magnetospheric activity. At the same time, it also obtained the largest sample of a rapid FRB outbreak event to date.
A series of discoveries show that FAST has become a powerful tool for observing celestial bodies in the field of low-frequency radio in China, and has also helped China to take a leading position in the world in this field.
The second is discovery in frequency domain science.
Hydrogen is the most abundant element in the universe and is one of the best tracers for studying the structure of galaxies, including the Milky Way. The high sensitivity and high survey efficiency enable FAST to map the neutral hydrogen of the Milky Way and extragalactic galaxies with high quality.
It not only helps scientists see a previously unknown section of the Milky Way's spiral arms, but also helps in the study of galaxies' baryon and dark matter.
In addition, it also measured the magnetic field around the dense cloud nucleus and found a coherent magnetic field structure, which is very important for the study of the formation process of stars, and also achieved a breakthrough in China's use of atomic radiation to detect the magnetic field of molecular clouds from 0 to 1.
There is,FAST is working with other telescopes to test the VLBI joint test, and to search SETI and its digital backend is working well.
At present, although there is no direct information and evidence that we have discovered extraterrestrial civilizations, it cannot be denied that some of the various galaxies discovered now have "entirely possible" evolved or some civilizations exist.
In addition to the above findings, from the analysis of the parameter space, FAST can explore more fields in the future. For example, long-period radio variable sources should be a possible important research direction.
The ever-changing universe is indeed elusive, but it just provides more possibilities for FAST to explore the stars.
Here, I want to say that,FAST can obtain a variety of high-quality data to help the original research of astronomical science in China, which is inseparable from the persistence of the operation and maintenance team.
Whether it is thunder and lightning or violent storms, it does not affect its normal operation in the slightest. Even if there is a problem, the operation and maintenance personnel will climb to an altitude of 100 meters in time to carry out synchronous repair and maintenance.
So,The successful exploration of FAST is the result of the dedicated efforts of people in different fields. Facing the future, we can look forward to looking into the deeper and farther universe through the "Chinese Sky Eye".