Year-end review: Major progress in China's space exploration in 2021

Looking back at the vast starry sky in 2021, the Chinese nation has burst into the most dazzling splendor: "Tianwen" landed on Mars, "Xihe" explored the sun, "Yinhe" patrolled the sky, and "Tiangong" toured the scenery...

This year, the major scientific projects to explore cosmic information also yielded fruitful results. The "China Sky Eye" discovered 201 pulsars, and the "Lasso" observed the highest energy photons, which amazed the international astronomical community; Chang'e 5 brought back the "soil" specialty of the moon, opening a new chapter in my country's lunar scientific research...

The Chinese nation is striding forward on the ambitious journey of exploring the vast ocean of stars.

01

Construction of the Tiangong is in full swing

my country's manned space flight enters the "space station era"

CCTV News video screenshot

The space station is the astronauts’ “space home” and the “space laboratory” for scientific research.

At 11:23 on April 29, at the Wenchang Space Launch Center in Hainan, the Long March 5B high-thrust carrier rocket successfully sent the core module of the Chinese space station into space with great force, marking the true harbinger of the space station era for my country's manned space program. So far, the in-orbit assembly and construction of the Chinese space station has been fully launched.

The China Space Station is a manned space station independently built and operated by China. It operates in low-Earth orbit for a long time and relies on cargo spacecraft to replenish propellant and consumables. It can meet the long-term living and working needs of astronauts in orbit. It represents the most comprehensive, complex, advanced and integrated scientific and technological achievements in today's aerospace field.

On June 17, astronauts Nie Haisheng, Liu Boming and Tang Hongbo aboard the Shenzhou XII manned spacecraft successively entered the Tianhe core module, marking the first time that Chinese people entered their own space station; on October 16, the Shenzhou XIII manned spacecraft successfully sent Zhai Zhigang, Wang Yaping and Ye Guangfu into space, and after entering the Tianhe core module, they began a six-month space stay; on November 7, Zhai Zhigang and Wang Yaping successively exited the Tianhe core module node module successfully, and Wang Yaping took the first step for a Chinese woman in extravehicular spacewalk; on December 9, the Shenzhou XIII astronaut crew gave their first space lesson at the Chinese space station.

02

It was found that the anti-galactic core structure originated from the galactic disk

Controversy over the origin of terminator structures

Astronomers already know that the Milky Way is not a smooth flat disk as traditionally thought, but a rippling river of stars. This understanding stems from the discovery of substructures in the direction opposite to the Milky Way's center, but where these substructures originate is controversial.

In May, a research paper by Chinese scientists published in the Astrophysical Journal ended the controversy. Researchers from the National Astronomical Observatory of the Chinese Academy of Sciences, China West Normal University and other institutions used data from the Guo Shoujing Telescope (LAMOST) and the Gaia satellite to conduct a "paternity test" on some substructures located in the anti-Galactic center direction and the Milky Way disk, and found that the anti-Galactic center substructure of the Milky Way is not the remains of dwarf galaxies accreted by the Milky Way, but part of the Milky Way's outer disk.

Using the telescope's observation data, the researchers searched for 589 member stars from the Monoceros ring, the Triangulum-Andromeda stream and the A13 structure, which is currently the largest sample of member stars of the anti-Galactic center structure.

The researchers compared the chemical element content, motion characteristics and energy angular momentum distribution of the member star samples with the Galactic disk and found that these member stars have similar near-circular motion orbits as the Galactic disk, and their metallic abundance is similar to that of the thick disk stars of the Galactic disk. These all prove that the substructure member stars may come from the thick disk of the Galactic disk.

However, further verification found that the abundance of alpha elements in these substructure member stars is significantly lower than that in the thick disk. In this regard, Li Jing, an associate professor at the School of Physics and Space Science of China West Normal University, explained that because there is still a lot of cold gas in the outer disk of the Milky Way, the density of molecular clouds in the outer disk is low compared to the inner disk, and the metallic abundance of chemical elements has not increased sufficiently.

Based on the motion characteristics and chemical DNA identification, astronomers speculate that these substructure members should belong to low-alpha abundance metal-poor outer disk stars. Xue Xiangxiang, a researcher at the National Astronomical Observatories of the Chinese Academy of Sciences, said: "This means that these anti-Galactic center substructures originated from the Milky Way disk."

03

Tianwen-1 lands on Mars

Searching for clues to the origin and evolution of Mars

Xinhua News Agency issued a photo provided by the National Space Administration

After crossing the vast starry sky and trekking for 297 days, at 7:18 on May 15, 2021, the Tianwen-1 lander and rover successfully landed in the pre-selected landing area in the southern part of Utopia Plain on Mars, reducing its speed from more than 20,000 kilometers per hour to zero in just 9 minutes. my country's first Mars exploration mission landing on Mars was a complete success.

At 10:40 on May 22, the Zhurong Mars rover safely left the landing platform, reached the surface of Mars, and began patrol exploration. China became the second country in the world to successfully land a rover on Mars.

Zhang Rongqiao, chief designer of my country's first Mars exploration mission, introduced that the Tianwen-1 mission is the first step for China to carry out planetary exploration. It has successfully completed the established mission goal of "realizing Mars orbit, landing and patrol in one mission", which will greatly promote the development of China's space science, especially planetary science research. At present, Tianwen-1 is in good orbital operation, and all 13 scientific payloads have been turned on to carry out scientific exploration activities, providing scientists with rich and high-quality scientific exploration data. Specifically, multi-element, first-hand Mars scientific data including Martian topography, surface material composition, underground structure, magnetic field, meteorology and space environment can be obtained. "Zhurong" is continuing to travel to the suspected ancient ocean and land boundary in the southern part of Utopia Plains, looking for clues to uncover the mystery of the origin and evolution of Mars.

It is worth mentioning that Tianwen-1 also captured a photo of the Earth and the Moon, a "deep space selfie" flight image, and sent back the first image of Mars. After arriving on the surface of Mars, on June 11, the first batch of scientific images of Tianwen-1 were released, marking the complete success of my country's first Mars exploration mission.

04

Lasso discovers highest energy photon yet

Breaking through the traditional understanding of galactic particle acceleration

High-altitude cosmic ray observatory "Laso". Image source: Institute of High Energy Physics, Chinese Academy of Sciences

The large-scale scientific project, the High Altitude Cosmic Ray Observatory "LHAASO", is located on Haizi Mountain with an average altitude of 4,410 meters in Daocheng, Sichuan. It is the world's largest high-altitude cosmic ray observation device. It took four years to complete and was completed on October 24, and officially entered the scientific operation stage.

The "Laso", which is being built and operated at the same time, has discovered photons with an energy of up to 1.4 peta-electron volts in the Milky Way. This is the highest energy photon ever observed by humans, breaking through the traditional human cognition of particle acceleration in the Milky Way and opening a new era of ultra-high energy gamma astronomy. On May 17, the relevant results paper was published online in the journal Nature.

05

FAST discovers 201 new pulsars

"China's Sky Eye" becomes the most powerful pulsar search tool

The world's largest single-aperture radio telescope, the Five-hundred-meter Aperture Spherical Radio Telescope (FAST), was completed and put into use on September 25, 2016. Photo by Xinhua News Agency reporter Ou Dongqu

Pulsars are the remains of massive stars that have died. They can emit highly periodic pulses with a period between 1.4 milliseconds and 23 seconds. Short-period pulsars, called millisecond pulsars, can rival the best atomic clocks on Earth. Therefore, pulsars are one of the main scientific targets for observations by large international radio telescopes.

As of April 2021, Chinese scientists have discovered 201 new pulsars through sky surveys conducted by the Five-hundred-meter Aperture Spherical Radio Telescope (FAST), including a group of the faintest pulsars, large-dispersion pulsars that challenge the contemporary model of electron distribution in the Milky Way, 40 millisecond pulsars, 16 pulsar binaries, a group of mode-changing and zero-out pulsars, and radio transient sources. The relevant research results were published as the cover article in Astronomy and Astrophysics Research on May 20.

FAST is known as the "China Sky Eye" and is equipped with a 19-beam L-band receiver. It is the world's most powerful pulsar search tool.

"Subsequent timing observations of these pulsars can be used to detect low-frequency gravitational waves from distant galaxies, and can also be used to establish pulsar time and space benchmarks. Some of these pulsars will become excellent tools for testing gravitational theories," said Han Jinlin, a researcher at the National Astronomical Observatory of the Chinese Academy of Sciences.

06

Chang'e 5 lunar sample distribution

It is expected to reveal the mysteries of lunar and planetary evolution

Photo by Xinhua News Agency reporter Jin Liwang

A gram of lunar soil can be viewed from a distance, and the stars can be measured over thousands of years. Lunar soil is formed by long-term weathering of lunar rocks on the lunar surface through meteorite and micrometeorite impacts, solar wind, cosmic ray radiation, and other space weathering processes. In addition to reflecting the material composition of the lunar surface itself, lunar soil is also an important carrier for recording the history of the interaction between the solar wind and the lunar surface, as well as the accretion of foreign matter.

On July 12, the Chang'e-5 mission held a distribution ceremony for the first batch of lunar scientific research samples. 31 applications from 13 scientific research institutions were approved, and a total of 17.4764 grams of samples were distributed, and lunar sample scientific research officially started. On October 20, the list of the second batch of lunar scientific research samples was announced, with a total of 17.936 grams of samples distributed.

Researchers will use lunar soil to study lunar surface processes, the age of volcanic activity, and lunar evolution processes, hoping to gain new insights into lunar and planetary evolution, and planetary habitability.

The Chang'e-5 lunar samples soon produced the first batch of scientific research results. On October 19, researchers from the Institute of Geology and Geophysics of the Chinese Academy of Sciences and the National Astronomical Observatory and other institutions discovered that the Chang'e-5 lunar samples were a new type of lunar mare basalt. The "youngest" basalts on the moon are 2 billion years old, and the source area of ​​the late magmatic activity in the region is not enriched with radioactive elements, and there is almost no water in the lunar mantle source area.

On December 13, the Purple Mountain Observatory of the Chinese Academy of Sciences and the Nanjing Institute of Geology and Paleontology found that the lunar samples had extremely high ilmenite content and were high-titanium basalts. Previously, other domestic research teams had found low-titanium and medium-titanium basalt types in lunar samples. Researchers speculated that the Chang'e 5 lunar landing area may have experienced multiple volcanic eruptions.

07

Suborbital reusable launch vehicle's first flight is successful

my country is moving from a space power to a space power

The development of reusable space transportation technology for round-trip travel between the earth and the sky is an important symbol of my country's progress from a major space power to a space power. The suborbital reusable vehicle can be used as a sub-stage of the lift-type rocket-powered reusable space transportation system and is a highly integrated aerospace technology.

On July 16, the suborbital reusable demonstration and verification project carrier developed by the First Academy of China Aerospace Science and Technology Corporation ignited and took off on time at the Jiuquan Satellite Launch Center. After completing the flight according to the set program, it landed smoothly at the Alxa Right Banner Airport. The maiden flight mission was a complete success.

Yang Yuguang, a researcher at the Second Academy of China Aerospace Science and Industry Corporation, said that the minimum apogee height of a suborbital trajectory is 80 to 100 kilometers, and theoretically it can reach the edge of the earth's gravity, that is, 1.5 million kilometers. The passive trajectory of a ballistic missile with a long range is suborbital. Suborbital is also widely used in sounding rockets and space tourism.

08

A world-class observatory site was discovered in Lenghu, Qinghai

It will become an extremely valuable strategic scarce resource in our country

Optical/infrared observation sites are extremely valuable strategic and scarce resources. Currently, the best sites recognized internationally are only the northern mountainous areas of Chile, Mauna Kaya Peak in Hawaii, USA, and the inland ice dome area of ​​Antarctica.

On August 18, Nature published a major scientific breakthrough in my country's site selection for astronomical observatories. After three years of continuous monitoring, Deng Licai's research team from the National Astronomical Observatory of the Chinese Academy of Sciences found that the optical observation conditions at the Lenghu site in Qinghai are superior to other site selections on the Qinghai-Tibet Plateau and can be compared with the internationally recognized best observatory sites.

The Lenghu area has abundant sunshine, very little precipitation, and clear night skies, and the weather conditions recorded in historical records are very good. Through field investigations in the Saishiteng Mountain area of ​​Lenghu, Deng Licai's research team determined that a fixed site at an elevation of 4,200 meters above sea level in the mountain area (Saishteng C area) would be selected. Since 2018, the number of clear nights, clear night background brightness, and meteorology in the area have been formally monitored for three years. By the end of 2020, conclusive data on the optical/infrared observation conditions of the Saishiteng Mountain were obtained.

In order to maximize the scientific benefits of the Lenghu site, Deng Licai said that the site resources should be protected as soon as possible to prevent factors such as light, dust, and vibration from affecting it; it is also necessary to attract internationally leading observation facilities to settle there, making it an important base for international optical astronomy research.

09

Launch of Xihe

my country achieves zero breakthrough in solar exploration

Solar Exploration Science and Technology Experimental Satellite "Xihe". Photo by Lei Chunming; Image source: National Space Administration

The sun is the closest star to the earth and is of great significance to the evolution of the earth and the development of human civilization. On October 14, my country's first solar exploration scientific and technological experimental satellite "Xihe" was successfully launched. my country officially entered the "sun exploration" era and achieved a breakthrough in solar exploration.

The full name of "Xihe" is the Solar Hα Spectrum Detection and Dual Super Platform Science and Technology Experimental Satellite. It weighs 508 kilograms and has a design life of 3 years. It operates in a sun-synchronous orbit at an altitude of 517 kilometers and can observe the sun continuously for 24 hours. Its main scientific payload is a solar space telescope.

From the launch vehicle to the satellite platform and then to the scientific payload, Xihe has created many firsts: the first time in the world to carry out solar Hα band spectral imaging space detection; the first time to adopt the new overall design method of "dynamic and static isolation and non-contact"; the first time to propose the new method of "active control of the payload cabin and passive control of the platform cabin"; the first time to realize the application of high-power, high-reliability and high-efficiency wireless energy transmission technology for satellites.

10

The second phase of the Milky Way Survey is launched

Will provide molecular gas distribution data over a wider area

Sky surveys are a basic means for humans to explore cosmic information. It is a systematic observation method that indiscriminately scans the scannable areas of the sky block by block, and discovers unknown celestial bodies by conducting a dragnet "census" of the sky.

The "Galactic Picture" survey is my country's only millimeter-wave survey project, which uses the 13.7-meter millimeter-wave radio telescope in Delingha, Qinghai, for astronomical observations. In November this year, the 10-year "Galactic Picture" second phase survey was launched, expanding the survey area to the range of plus or minus 10 degrees of galactic latitude near the galactic plane, which will provide a wider range of molecular gas distribution data for multi-band astronomical research.

The first phase of the "Galactic Panorama" sky survey project lasted for 10 years from November 2011 to the end of April 2021. It completed the detection coverage of 2,400 square degrees within the range of plus or minus 5 degrees of galactic latitude, and established a millimeter-wave molecular spectral line database.

Yang Ji, a researcher at the Purple Mountain Observatory of the Chinese Academy of Sciences and the chief director of the "Galactic Panorama" survey project, pointed out that whether it is the first or second phase project, the "carbon monoxide molecular spectrum line" is the observation core of the "Galactic Panorama" project because it can help scientists reveal the properties of molecular gas such as temperature and density.

At present, my country has a number of influential astronomical survey projects. In addition to the "Galactic Picture Scroll" plan, there are also spectral surveys based on LAMOST and pulsar surveys based on FAST.

◎ Science and Technology Daily reporter Tang Fang

Source: Science and Technology Daily

Editor: Wang Yu

Review: Julie

Final review: Liu Haiying