This photo she took made people rethink the universe and themselves

Voyager 1 helped humans further study the Jupiter and Saturn systems with higher quality data. The photos of the Earth it took during its long roaming - the "Pale Blue Dot" - have significance beyond the scope of astronomy and have become one of the important starting points for human philosophical thinking about the universe, the Earth and human beings themselves. Voyager 1 is also the first man-made celestial body to leave the solar system and the man-made celestial body farthest from the Earth so far. Its success also directly laid a solid foundation for Voyager 2 to complete the feat of "planetary tour" later.

Written by | Wang Shanqin

As the pathfinders of the "Planet Tour" project, the success of Pioneer 10 and Pioneer 11 opened two windows for humans to explore the outer planets (Jupiter, Saturn, Uranus and Neptune). However, on December 16, 1971, before the two probes were launched, NASA announced the cancellation of the "Planet Tour" project. At this time, it was only two years since the project was officially launched (1969).

The reason for the cancellation of the "Grand Tour of the Planets" project was funding. At the time, the budget for the project was as high as $1 billion, equivalent to about $5 billion today. On the other hand, since 1965, NASA's funding has been decreasing year by year; after the Apollo moon landing program was successful in 1969, President Nixon, who took office in the same year, further cut NASA's annual funding. In 1971, NASA could only choose between the space shuttle project and the "Grand Tour of the Planets" project. NASA chose the space shuttle project.

Voyager: Rebirth of the "Grand Tour of Planets"

The cancellation of the "Planet Tour" project is undoubtedly a huge tragedy.

Fortunately, when NASA's Outer Planets Working Group recommended the "Planet Tours" project in 1969, it also recommended an alternative plan: to establish a project that only explores Jupiter and Saturn, which has a much lower budget. In 1971, at the last discussion and voting meeting on the "Planet Tours" project, the expert group emphasized this alternative plan while approving the project. When NASA finally decided to cancel the "Planet Tours" project, it also gave high praise to the alternative plan.

This alternative plan gave the "Planet Tour" project a chance to be reborn. In January 1972, the Jet Propulsion Laboratory (JPL) began to prepare for this alternative project; in May of the same year, NASA officially approved this alternative project, which was the "Mariner Jupiter-Saturn" (MJS) project.

The MJS project will launch two identical probes, with the second probe serving as a spare for the first probe. When the MJS project was proposed, JPL had already operated Mariner 1 to 9, which explored Mercury, Venus, and Mars, and Mariner 10 was about to be launched. The two probes of the MJS project were therefore named "Mariner 11" and "Mariner 12" respectively. The budget for the project was $360 million.

Since Mariner 11 and Mariner 12 of the MJS project explored outer planets, which had significant differences in exploration targets from other probes in the Mariner series, they were renamed "Voyager 1" and "Voyager 2" respectively on March 7, 1977, and no longer belonged to the Mariner series, but were still operated by the JPL team.

Voyager 1's exploration targets are Jupiter, Saturn and Titan, and its orbital code is "JST", which are the first letters of the English letters of the above three celestial bodies.

Schematic diagram of the orbits of Voyager 1 and Voyager 2. Voyager 1 moves in the direction of "JST" and Voyager 2 moves in the direction of "JSX". There are two possibilities for X, X=TB means that it includes the Titan flyby mission (in case Voyager 1 fails); X=U means that it includes the Uranus flyby mission (in case Voyager 1 succeeds). The time scale on the orbit is in units of 0.5 years. 丨Image source: NASA; Translation: Wang Shanqin

Structure and Instruments

Voyager 1 has a mass of 825.5 kg, of which the spacecraft itself has a mass of 721.9 kg. It has 16 MR-103 hydrazine thrusters for attitude control, 8 spare thrusters, a three-axis stabilized gyroscope, a celestial coordinate reference device, a radio communication system, an energy system, 11 scientific instruments, a solid engine for mid-course orbit change, and 8 propulsion rocket engines.

Models of Voyager 1 and 2 | Image source: NASA/JPL

Voyager 1's radio communication system includes a 3.7-meter-diameter parabolic high-gain antenna that receives signal commands from three Deep Space Network (DSN) sites on Earth and sends the resulting data to the DSN.

An engineer with Voyager's unfinished high-gain antenna on July 9, 1976 | Image source: NASA/JPL

Voyager 1 also had a data storage device, a Digital Tape Recorder (DTR), which could hold 64 kilobytes of data, allowing it to send images with a time delay. In contrast, Pioneer 10 and 11 did not have DTRs, so the data they captured had to be sent immediately.

Voyager 1's electrical energy is provided by three radioisotope thermal generators (RTGs). Each RTG contains 24 compressed plutonium-238 oxide pellets, so it is also called a plutonium nuclear battery. When it is just launched, the heat generated by the RTG can produce about 470 watts of electrical power. Due to the decay of radioactive materials, the power of the RTG will continue to decrease.

A unit of the radioisotope thermoelectric generator in Voyager 1 and 2. Image credit: NASA/JPL

Voyager 1's scientific instruments include: Imaging Science System, Radio Science System, Infrared Interferometer Spectrometer, Ultraviolet Spectrometer, Triaxial Fluxgate Magnetometer, Plasma Spectrometer, Low Energy Charged Particle Instrument, Cosmic Ray System, Planetary Radio Astronomy Investigation System, Photopolarimeter System, and Plasma Wave Subsystem.

Structural diagram of Voyager 1 and 2 | Image source: NASA/JPL

Among the instruments on Voyager 1, the imaging science system is responsible for taking images. It weighs 38.2 kilograms and includes a long-focus narrow field camera and a short-focus wide field camera, which use telescopes with apertures of 17.7 cm and 5.7 cm respectively. The filters on both cameras cover multiple bands from ultraviolet to visible light. Through these filters, the camera can take monochrome images, which are synthesized by astronomers into magnificent color pictures with a resolution of up to several kilometers per pixel.

According to previous calculations, the launch window for the original "Planet Tour" project spacecraft and the later replacement Voyagers 1 and 2 was between 1976 and 1980. On September 5, 1977, Voyager 1 was launched on the Titan IIIE-Centaur rocket. 16 days earlier (August 20, 1977), Voyager 2 had already been launched on the same rocket. Voyager 1 was delayed several times before launch, resulting in this reversed order. However, under the design of orbital dynamics experts, Voyager 1 will cross the asteroid belt and visit Jupiter and Saturn earlier than Voyager 2.

Voyager 1 takes off on a rocket | Image source: NASA

On December 10, 1977, Voyager 1 entered the asteroid belt. On December 19, 1977, Voyager 1 flew ahead of Voyager 2. On September 8, 1978, Voyager 1 left the asteroid belt.

Flyby of the Jupiter system

On January 6, 1979, Voyager 1 began observing Jupiter.

Part of Jupiter's Great Red Spot was photographed by Voyager 1 on February 25, 1979. At that time, Voyager 1 was 9.2 million kilometers away from Jupiter. The resolution of the image reached 160 kilometers. 丨Image source: NASA/JPL

Voyager 1 took multiple photos of Jupiter over a 28-day period between January 6 and February 3, 1979. During this period, Voyager 1 flew from 58 million kilometers to 31 million kilometers from Jupiter. Later, these photos were stitched together into a movie.

This is a movie composed of photos taken by Voyager 1 between January 6 and February 3, 1979. In order to show the changes in the features of the same surface, photos taken every 10 hours (Jupiter's rotation period) were selected to stitch together this video. During this period, the position of Jupiter's Great Red Spot remained almost unchanged, but it rotated at a high speed, and clouds at different latitudes showed different moving characteristics. The black dots that appear in the video are the projections of Jupiter's satellites, and the white dots are Jupiter's satellites themselves. 丨Video source: NASA/JPL

On February 10, 1979, Voyager 1 entered the Jupiter system. In early March, it discovered a thin ring around Jupiter, less than 30 kilometers thick. This was the first time that humans confirmed that Jupiter had rings. On March 4 and 5, 1979, Voyager 1 discovered Jupiter's moons, Jupiter's moons, and Jupiter's moons, Jupiter's moons.

Jupiter's rings photographed by Voyager 1 | Image source: NASA/JPL

At 12:05:26 on March 5, 1979, Voyager 1 reached the periapsis of Jupiter, at which time it was about 280,000 kilometers from the top of Jupiter's clouds. Before and after the flyby of Jupiter, it took a large number of high-quality images and detected Jupiter's magnetic field, gravity field, atmosphere, etc.

False color image of Jupiter's Great Red Spot synthesized from data obtained by Voyager 1 | Image source: NASA/JPL

After flying past Jupiter, Voyager 1 flew past Io (20,570 km away) and Europa (733,760 km away) on the same day.

A photo of Jupiter, Io (left) and Europa (right) taken by Voyager 1 in March 1979. Image source: NASA

Compared to the distances at which Pioneer 10 and Pioneer 11 flew past Io (357,000 km and 314,000 km respectively), Voyager 1 was much closer to Io (20,570 km), allowing it to observe a great deal of detail on Io.

An image of Io (left) merged from multiple images of Io taken by Voyager 1 at an altitude of 450,000 kilometers on March 5, 1979, and a heart-shaped area formed by the falling material of the Pele volcano after the eruption (right). Near the Pele crater is the Loki volcano. The black crack in the center of the heart-shaped area is the crater, and the heart-shaped area was formed after the material erupted after the volcanic eruption fell. | Image source: NASA/JPL

Voyager 1 directly photographed the eruption of a volcano on Io. This is the first time that humans have discovered a volcanic eruption on a celestial body other than Earth. Interestingly, shortly before this discovery, astronomers had predicted the existence of volcanic activity on Io based on theoretical calculations. Studies have shown that Io is the most volcanically active celestial body in the solar system. The sulfur-rich materials erupted by its volcanoes fell on its surface, forming a red, orange and yellow surface.

Part of Io photographed by Voyager 1 on March 4, 1979 (left) and part of Io photographed by Voyager 1 on March 5, 1979 (right). At that time, Voyager 1 was 490,000 kilometers away from Io and 128,500 kilometers away from Io respectively. The left picture shows the scene of the eruption of Rocky Volcano, and the material ejected by the volcano was thrown more than 160 kilometers high. Image credit: NASA/JPL

Although Voyager 1 flew past Europa at a greater distance than Pioneer 10 and Pioneer 11 (321/586,700 km), it still obtained higher-resolution images with its high-quality imaging system. The images it took showed that there were criss-crossing cracks on the surface of Europa. Astronomers at the time inferred that these cracks came from surface fractures or tectonic processes.

This photo of Europa taken by Voyager 1 on March 2, 1979, at a distance of 2,869,252 kilometers. The dark lines on the surface are cracks on Europa's surface. Image source: NASA/JPL

On March 6, 1979, Voyager 1 flew past Ganymede (114,710 km away) and Callisto (126,400 km away) successively. Since the flyby distance was much smaller than that of Pioneer 10 and Pioneer 11, it obtained higher quality images of Ganymede and Callisto.

A partial view of Ganymede (left) taken by Voyager 1 on March 5, 1979, and a partial view of Callisto (right) taken by Voyager 1 on March 6, 1979. When the photo was taken, the distances of Voyager 1 to Ganymede and Callisto were 246,000 kilometers and 200,000 kilometers respectively. Image source: NASA/JPL

Although Voyager 1 observed Jupiter for about three months, it was only able to detect Jupiter's magnetic field and radiation for 48 hours before and after reaching its periapsis. The detailed observation of Jupiter's rings and satellites lasted only a few days. During this period, Voyager 1 discovered 8 satellites of Jupiter.

During several months of imaging observations and several days of close observations, Voyager 1 obtained a large amount of data on the Jupiter system, which provided important basis for planetary scientists to further study the Jupiter system.

Flyby of the Saturn system

On April 9, 1979, Voyager 1 completed its orbit correction and flew towards Saturn. To avoid colliding with Titan, it made another orbit correction on October 10, 1979. On August 22, 1980, Voyager 1 began observing Saturn.

On November 12, 1980, Voyager 1 entered the Saturn system and flew past Titan on the same day. The closest distance to the surface of Titan was only 3,915 kilometers, which was 1/90 of the distance when Pioneer 11 flew past Titan (362,962 kilometers).

On November 12, 1980, Voyager 1 took this photo of Titan from a distance of 435,000 kilometers. The top of Titan is covered with thick fog. Image credit: NASA/JPL

Data from the Voyager 1 spectrometer indicate that Titan's atmosphere contains methane, ethane, and a variety of other organic compounds, as well as large amounts of nitrogen. However, the thick organic haze in Titan's atmosphere makes the images obtained by Voyager 1 look featureless.

Based on Voyager 1 radio occultation data, astronomers inferred that Titan's diameter is 5152 kilometers, the surface temperature is about 94 K, and the atmospheric pressure is 1.47 bar (1 bar = 100,000 Pascals, the standard atmospheric pressure on Earth is 1.01325 bar). Its data also show that Titan has a dense atmosphere and may have liquid matter on its surface.

On November 12, 1980, Voyager 1 flew past Tethys (415,670 km away). At 23:46:30 on the same day, Voyager 1 reached Saturn's periapsis (the point closest to the gravitational center of the central celestial body), at which time it was 126,000 km away from Saturn's cloud tops.

Saturn's rings were photographed by Voyager 1 on November 13, 1980, when it was 1.5 million kilometers from Saturn. Image credit: NASA/JPL

On November 13, 1980, Voyager 1 flew past Mimas (88,440 km away), Enceladus (202,040 km away), Rhea (73,980 km away), and Titan (880,440 km away) on the same day.

On November 12, 1980, Voyager 2 took photos of Mimas (left, 425,000 kilometers away) and Tethys (right, 1.2 million kilometers away). In these pictures, Crater Herschel on the upper right of Mimas and Ithaca Chasma on Tethys are clearly visible. Image credit: NASA/JPL

On November 12, 1980, Voyager 2 took a photo of Titan (left, 240,000 kilometers away) and Rhea (right, 73,000 kilometers away). The many craters on their surfaces are clearly visible. | Image source: NASA/JPL

Voyager 1's observation mission of the Saturn system ended on November 14, 1980. During the flyby of the Saturn system, Voyager 1 observed the chemical composition of Saturn's upper atmosphere, the complex structure of Saturn's rings, Saturn's auroras, Titan and several other previously confirmed satellites, and discovered five new satellites of Saturn and Saturn's G ring.

The rings of Saturn were photographed by Voyager 1 on November 16, 1980, when it was 5.3 million kilometers away from Saturn. The shadows formed by the sunlight shining on Saturn are cast on the rings of Saturn. Image source: NASA/JPL

When Voyager 1 flew close to Titan, Titan's gravity caused it to pass through Saturn's South Pole and fly away from the ecliptic plane (the orbital plane of the Earth's revolution is the ecliptic, and the orbital planes of other planets in the solar system around the Sun are basically coplanar with the ecliptic plane), and then fly away from the solar system.

A family portrait of the solar system and the "Pale Blue Dot"

On February 14, 1990, Voyager 1, which had drifted in the empty solar system for more than 12 years, was about 6 billion kilometers away from the Earth. At this time, it was 32 degrees above the ecliptic plane, suitable for photographing several major planets in the solar system. The Voyager team issued an order to let it point in the direction of the sun and took 60 pictures, forming a family portrait of the solar system. In order to avoid overexposure to the sun, the exposure time of each photo was only 0.005 seconds.

This family portrait shows Jupiter, Earth, Venus, Saturn, Uranus and Neptune in the solar system. Mercury cannot be identified because it is too close to the sun. Mars is also not identifiable because its position at the time made it just a crescent-shaped object from the perspective of Voyager 1.

A family portrait of the solar system taken by Voyager 1 on February 14, 1990. From left to right: Jupiter, Earth, Venus, Saturn, Uranus and Neptune. 丨Image source: NASA/JPL

The most famous of the family portraits is the image of Earth, in which the Earth is just a tiny dot of 0.12 pixels, almost drowned out by the colorful bands of light created by sunlight reflecting off the camera.

An image of the Earth taken by Voyager 1 on February 14, 1990. The pale dot in the bright red band on the far right is our Earth. Image credit: NASA/JPL

This photo inspired Carl Sagan (1934-1996), a famous astronomer, astrobiologist, popular science writer and science fiction writer, who called the Earth in the photo the "Pale Blue Dot" and published his book Pale Blue Dot: A Vision of the Human Future in Space in 1994.

In the book, Sagan said emotionally: "Think about that dot again. That's here, that's home, that's us. On this dot, everyone you love, everyone you know, everyone you've ever heard of, everyone, no matter who they are, has lived out their lives." "Some say astronomy is humbling and character-building. Perhaps nothing shows the folly of human arrogance better than this distant photo of our tiny world. To me, this photo emphasizes our responsibility: to treat each other more kindly, to protect and cherish this pale blue dot - the only home we know of." [Note 1]

The marriage of this picture taken by Voyager 1 and the book written by Sagan gave the Earth the nickname "Pale Blue Dot". This name quickly spread and broke through the circle, becoming one of the most important entry points for human beings to think about the Earth and the universe.

Flying beyond the solar system

After completing the exploration of the outer planetary system, astronomers launched the Voyager Interstellar Mission (VIM) for the Voyagers in 1989. At that time, Voyager 1 was 40 AU (1 AU is 149.6 million km) from the Earth.

VIM mainly detects phenomena related to the solar wind. VIM is divided into three phases: detecting the termination shock, detecting the heliosheath, and detecting interstellar space.

The heliosphere is a huge bubble formed around the sun by the solar wind (the light gray area in the figure below). The boundary between it and interstellar space is the heliopause, where solar wind particles stop. When the solar wind blows to the area close to the heliopause, it will come into contact with the interstellar medium and be hindered by the interstellar medium, forming a terminal shock wave. This area is called the "terminal shock wave region."

At one end of the direction of the sun's movement, the area between the termination shock zone and the heliopause is shaped like a scabbard or sword sheath, so it is called the "heliospheric sheath."

Schematic diagram of the heliosphere, termination shock, heliospheric sheath, heliopause, and bow shock. Image source: NASA/Goddard/Walt Feimer; Translation: Wang Shanqin

Therefore, in the direction away from the sun, from the inside to the outside, there are the termination shock region, the heliosphere sheath and the heliopause. The heliopause impacts the interstellar medium, forming a bow shock. According to the definition of some astronomers, the interstellar space is beyond the heliopause.

On February 17, 1998, Voyager 1 surpassed Pioneer 10, at which time it was about 69.419 AU (about 10.41 billion kilometers) from the Earth. Since then, it has been the spacecraft farthest from the Sun.

On December 17, 2004, Voyager 1 passed through the termination shock region and entered the heliosphere. In June 2012, astronomers discovered that the number of high-energy particles received by Voyager 1 from interstellar space increased dramatically, so they judged that it was about to pass through the heliopause.

On August 25, 2012, Voyager 1 passed through the heliopause, at a distance of 121 AU (about 18.15 billion kilometers) from Earth. According to some astronomers, Voyager 1 became the first spacecraft in history to enter interstellar space on that day. [Note 2]

To celebrate Voyager 1's arrival in interstellar space, astronomers took this radio image of Voyager 1 using the Very Long Baseline Array (VLBA) on February 21, 2013.

A radio photo of Voyager 1 taken by the Very Long Baseline Array (VLBA) on February 21, 2013. Image credit: NRAO/AUI/NSF

As of February 18, 2023, Voyager 1 is 159.1 AU (about 23.801 billion km) from the Sun [Note 3]. Now, its speed relative to the Sun has reached 17 kilometers per second (3.57 AU per year), far exceeding the third cosmic velocity (the speed of escaping the Sun's gravity and leaving the solar system) at its location, so it will continue to move away from the Sun and will continue to move toward the center of the Milky Way. It can also fly out of the Milky Way and roam in the universe outside the Milky Way.

Golden Record for Aliens

In order to allow possible aliens to have a chance to learn about the Earth, astronomers placed a 12-inch (30 cm) diameter gold-plated copper disk on Voyager 1 and 2, which recorded the location of the Earth and human information. These two gold-plated copper disks are the famous "Golden Records".

The Golden Record on Voyager 1 | Image source: NASA/JPL

The golden record includes greetings in 55 languages ​​(including Chinese Mandarin, Cantonese, Minnan dialect, and Wu dialect), 35 sounds of life on Earth, 90 minutes of "Voices of the Earth" (including the sounds of whales, babies crying, waves hitting the shore, and 27 world-famous songs on Earth, including the Chinese guqin piece "Flowing Water" and Mozart's "The Magic Flute"); 115 photos (including human mathematics, physics, the solar system and the planets within it, animals, plants, DNA, human anatomy and reproduction on Earth, the topography and scenery of some areas on Earth, food, architecture, human daily life, etc.) and recorded greetings from some politicians at the time.

The meaning of the information on the Golden Record | Image source: NASA/JPL

The solar system and 15 lines in the lower left corner of the record cover and the dumbbell-shaped figure in the lower right corner are the same as the nameplates of Pioneer 10 and 11. Their significance has been introduced in the article introducing Pioneer 10 ("Pioneer in Exploring the Frontier of the Solar System: Pioneer 10丨Planetary Tour"), so they will not be repeated here.

In the upper left corner of the record cover is a drawing of a phonograph record and a stylus. The binary symbols around it represent the time it takes for the record to rotate once, which can be calculated to be 3.6 seconds. Below the large circle is a side view of the record and stylus, which shows that it takes about 1 hour to play the record.

The upper right corner of the album cover shows the waveform of the image signal, the binary symbol of the scanning time (8 milliseconds), and the method of drawing the straight lines that make up the image. The bottom shows that if the decoding is correct, this picture is a circle.

Great achievements and great sacrifices

Although Voyager 1 was not the first probe to closely explore the Jupiter and Saturn systems, it obtained better images of the two system members than Pioneer 10 and 11. In addition, it discovered volcanic eruptions on Io, Jupiter's rings, 8 new satellites of Jupiter, flew over Titan, discovered Saturn's G ring, 5 new satellites of Saturn, etc. Its observations of the Jupiter and Saturn systems have further deepened mankind's understanding of the physical, chemical and even biological properties of these two gas giants, their satellites and rings.

A "family photo" of Jupiter (upper right), Io (upper left), Europa (middle), Ganymede (lower left) and Callisto (lower right) taken by Voyager 1. These pictures are not taken from the same photo, but are composed of multiple photos. Their sizes in the picture are not to scale. | Image source: NASA

The significance of the photo of the Earth ("Pale Blue Dot") taken by Voyager 1 during its long roaming goes beyond the scope of astronomy: after Sagan's infectious expression was widely circulated, this image of the "Pale Blue Dot" became one of the important starting points for human philosophical thinking about the universe, the Earth and human beings themselves, enabling people to have a direct understanding of the smallness, loneliness, fragility and preciousness of the Earth, and also enabling humans to have an intuitive experience of the vastness of the universe.

In addition, Voyager 1 is the first man-made object to leave the solar system. It is also the farthest man-made object from the Earth so far. Due to its huge speed, all other man-made objects that have been launched so far cannot break its record in terms of distance.

Although Voyager 1 achieved many outstanding achievements, it also paid a price. Due to its close exploration of Titan, its orbit was significantly changed by Titan's gravity, and it was unable to fly past Saturn and then head to Uranus and Neptune. This was the plan from the beginning.

At that time, the Voyager team even made a plan: if Voyager 1 failed to explore Titan, Voyager 2 would repeat the mission of Voyager 1. We should be thankful that Voyager 1 successfully completed the exploration plan of Titan, so that Voyager 2 can realize the mission of exploring Uranus and Neptune, thus basically realizing the ambitious "planetary tour" plan. In other words, Voyager 2's ability to complete the feat of "planetary tour" is thanks to the sacrifice and accomplishment of Voyager 1.

Notes

[Note 1] Original text: "Consider again that dot. That's here, that's home, that's us. On it you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. ""It has been said that astronomy is a humbling and character-building experience. There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. To me, it underscores our responsibility to deal more kindly everyone with one another, and to preserve and cherish the pale blue dot, the only home we've ever known." Readers interested in other passages can enter the following link:
https://www.goodreads.com/quotes/337712-from-this-distant-vantage-point-the-earth-might-not-seem.

[Note 2] Astronomers have a dispute over the boundary of interstellar space. Some astronomers believe that the heliosphere is not the boundary between the solar system and interstellar space. This is because astronomers believe that there are a large number of small celestial bodies orbiting the sun in the distance, and the area they form is called the "Oort cloud." If the outer edge of the Oort cloud is regarded as the frontier of the solar system, then Voyager 1 will need to fly for nearly 30,000 years to leave the boundary of the solar system and enter interstellar space.

[Note 3] For real-time updates of the distance between Voyager 1 (and Voyager 2) and other information, see:

https://voyager.jpl.nasa.gov/mission/status/

This article is supported by the Science Popularization China Starry Sky Project

Produced by: China Association for Science and Technology Department of Science Popularization

Producer: China Science and Technology Press Co., Ltd., Beijing Zhongke Xinghe Culture Media Co., Ltd.

Produced by: Science Popularization China

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