What is the significance of the VLBI long base lines in the depths of Qinling?

On June 22, the 40 -meter radio telescope of the National Academy of Sciences at the National Academy of Sciences, located in Beidou Village (Hoiping Village), Luoan County, Shaanxi, successfully obtained the VLBI long -found line pattern. What is this stripe? Is it so strong that scientists spend so strong because this stripe looks good?

Why do we do VLBI?

The full name of VLBI in Chinese is "very long baseline interference measurement technology" or "very long baseline interference measurement measuring instrument". The previous name corresponds to a measurement technology, and the latter name corresponds to the instrument and equipment.

VLBI is one of the most observed observation methods in astronomy, which can reach the corner resolution of the sub -cotton second. In order to see the artificial aircraft far away from the earth, VLBI technology has been used in my country's moon ("Chang'e") and Mars detection ("Tianwen"). Heavy responsibility.

It is also thanks to the high -strength skills of VLBI in the corner resolution, scientists successfully used the black hole ("photo"). Luonan 40-meter radio telescope has successfully obtained the VLBI long-found line pattern on both baselines in Shanghai-Luonan and Urumqi-Luonan, indicating that the radio telescope already has VLBI observation capabilities, which will become domestic VLBI observation tasks and carry out pulse pulses. The important part of the high -precision position measurement and participation in deep space detection tasks such as the star body.

The first black hole "photo" taken by humans, and the "photo" combination of "photo" in the center of the galaxy (picture source: ESO)

In addition, the State Time Center, as the only institution in my country, professional, and comprehensive scientific research on time frequency, the benchmark of the pulse time is one of the important research directions of the unit. At present, the National Time Center is based on the timing observation of the pulse star of the radio telescope, and VLBI can measure the position of the pulse star.

By participating in the joint observation of VLBI, the site coordinates of the 40 -meter radio telescope of Lounan can be more accurate. At the same time, the performance of the entire system (multiple indicators and parameters) is measured, which is equivalent to conducting high -end "physical examinations" of the entire system. It helps to improve the overall performance of the 40 -meter radio telescope of Luonan, and then greatly improve the performance of pulse star timing observation. In this way, participating in VLBI is really self -interest. Isn't it beautiful?

Luonan 40 -meter antenna (picture source: Author shooting)

VLBI is so powerful, what exactly does it look like?

The lone wood is not a forest, and a single radio telescope cannot be VLBI. Generally speaking, VLBI is two or multi -radio telescopes, which observe the same target source and at the same time at the same frequency. Below is an early VLBI system introduction chart, from NASA.

VLBI system schematic diagram (picture source: NASA)

How to click the picture in this treasure? The radio signal emitted by the distant celestial body of the universe (this picture is a star -like body QUSAR). When it is near the celestial bodies, there is a spherical wave, just like the ripples caused by throwing stones in the pond. As the distance increases, when it spreads to the earth, the circle circle circle is no longer visible. It is no longer a spherical wave, but is regarded as a plane wave, that is, the round shape of the spherical wave is hot.

As mentioned above, VLBI is the same frequency observation of the same target source at the same time, and these antennas form a VLBI network. For a VLBI network, a very important feature is its UV coverage. The English covered by UV is called UV Coverge. It is not clear about the three or two sentences. Having said that, show you what the UV covers looks like.

Under different cases, the UV coverage of the European VLBI network (picture source: EVN)

The picture on the left is a UV coverage of the European VLBI network. Is it like a pile of spider webs? The horizontal axis is U, the vertical axis is V, and it is UV together. U and V's units are kilometers (km). The yellow characters on the left in the figure are the antennas used to get this UV coverage. Now let's take a look at the picture on the right. The range of the value of the spider web u and V has become larger. This change is mainly the contribution of the two VLBI stations in Shanghai and Urumqi in our country.

Yes, with our two stations, the UV coverage is obviously more than. So what are the particular attention of these rings? Chinese Kung Fu pays attention to a rigidity and tenderness, one inch, one inch, one inch, one inch, one inch, and the same is true of UV coverage. In the UV coverage, not only there must be large circles, but also small circles. The distribution of antennas in the VLBI network is required, it is best to have a distance from distance.

What will the VLBI in the depths of Qinling bring us?

At present, China VLBI Network (CVN) is composed of four stations: Shanghai, Beijing, Kunming and Urumqi. The four baselines of the four stations of CVN are basically long baselines, and the middle of this array is empty.

The National Time Center Luonan 40m radio telescope is located in Qinling Mountains in Shaanxi. From a geographical point of view, it can enrich and improve the UV coverage of CVN.Children who have been abused by the Olympics may remember to arrange and combine, four stations and six baselines. This is a combination problem. After joining Luonan Station, it becomes 10 base lines of five stations!Of course, if you add FAST in the future, wait, the picture is too beautiful, I dare not imagine.Produced: Popular Science China

Production: Luo Jintao (National Time Center of the Chinese Academy of Sciences)

Producer: China Science Popularization Expo

The China Science Popularization Expo is the Science Popular Science Platform of the Chinese Academy of Sciences. It is sponsored by the Computer Network Information Center of the Chinese Academy of Sciences. Relying on the high -end scientific resources of the Chinese Academy of Sciences, it is committed to spreading cutting -edge scientific knowledge and providing fun science and education services.

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