Naming celestial bodies: seemingly simple but with a lot of knowledge behind it

On April 24, at the launch ceremony of the main event of "China Space Day", the National Space Administration and the Chinese Academy of Sciences jointly released China's first global image of Mars, and also identified geographical entities near the landing site. According to the application naming rules, the International Astronomical Union named 22 of the geographical entities after famous Chinese historical and cultural villages and towns. Place names such as Pingle, Xibaipo and Mohe will be forever engraved on Mars. In February 2019, based on my country's application, the International Astronomical Union also named 5 lunar geographical entities near the landing site of Chang'e 4. At present, there are many names from China for the moon, Mars and even more distant asteroids. So, what are the special requirements for naming celestial bodies?

Distribution map of 22 geographical entities on Mars (Source: National Space Administration)

The names of celestial bodies and places are rich and varied

Readers who have seen maps know that there are various place names on them. The purpose is to better identify the area and make people remember it. Astronomers will also give a name to a new celestial body after discovering it.

Modern astronomical observations and deep space exploration have also discovered a large number of asteroids and satellites, and a large number of new names have been born by observing their topography.

Naming solar system objects after mythological stories is a long tradition in the history of astronomy. As early as 1610, Italian astronomer Galileo discovered four large satellites of Jupiter using a homemade telescope. Another astronomer, Simon Marius, named these four satellites Io, Europa, Ganymede and Christos, all of whom were lovers of the main god Jupiter (Jupiter).

In 1975, the International Astronomical Union also stipulated that newly discovered satellites of Jupiter should be named after Jupiter's lovers or their descendants. Later, the tradition of naming celestial bodies after gods continued to asteroids. For example, in 1801, Italian astronomer Piazzi announced an asteroid and named it after Ceres, the goddess of agriculture and harvest in Roman mythology.

As more and more celestial bodies were discovered in the solar system, their names were extended from gods to various names. Phobos is the son of Mars, the god of war, and is covered with impact craters. The largest of these craters is named Stickney, which was named after the discoverer Hall's wife.

Looking back to the past and looking back to the present, the naming of the moon and other celestial bodies and landforms in the solar system reflects a country's astronomical observation and deep space exploration capabilities, and is a reflection of the country's overall level of scientific and technological development.

Naming rules are very particular

So far, there are more than 2,000 place names in the Martian place name database, but there are very few place names named by Chinese people. Although my country is the second country in the world after the United States to successfully land and operate a Mars rover, my country has been unlucky in history. Astronomical observation started too late and missed the golden age of celestial body naming. Modern astronomical observation originated in Europe and the United States. In the early days, the naming of lunar and Martian geographical entities was very arbitrary. Astronomers used telescopes to observe these celestial bodies and named the geographical entities they saw at will. It can be said to be the golden age of free naming.

In 1919, the International Astronomical Union was established, and the naming and allocation of celestial bodies was one of its main tasks. In 1958, the International Astronomical Union's Commission on the Names of Mars sorted out and confirmed the names of early astronomers, forming the earliest unified list of Martian place names.

Subsequently, the International Astronomical Union developed standard documents for the naming of planetary names, including the names of the moon, Mars and other asteroids must be certified by them, ending the era when discoverers enjoyed full naming rights.

Although anyone has the right to submit new celestial names to the International Astronomical Union, the review authority must be held by the relevant organizations under the International Astronomical Union.

According to the naming rules, when applying for names for celestial bodies, such as topography and landforms, the names must first be simple, clear and distinct, and cannot be confused with existing names. Secondly, it is necessary to avoid the phenomenon of duplicate names, and avoid using the same name for two or more geographical units. Thirdly, the names cannot have political, military or religious connotations, and avoid the names on celestial bodies causing disputes on the ground. Finally, planet discoverers cannot name celestial bodies after themselves, but can name them after family members, friends and outstanding figures.

In addition, unless the various celestial bodies discovered by astronomers have great scientific research value, they cannot be given official names to geographical units smaller than 100 meters.

After the IAU established the above rules, it is quite difficult to name celestial bodies, even the nearest lunar terrain. Most importantly, when a country submits the celestial bodies and geographical units on the celestial bodies to be named to the Small Bodies Committee of the IAU, they must be reviewed by the Naming Working Group. After the new name is reviewed and approved, it must also be approved by the IAU General Assembly before it can be officially certified as a formal name.

Naming is no longer limited to one

Myths have always been an important source of naming for celestial bodies. This is true for all major planets. For example, Mars is named after the god of war, Mars; Jupiter is named after the main god Jupiter; Saturn is named after the god of agriculture, Saturn; Ceres is named after the god of cereals, Ceres; and the asteroids are generally named after subordinate gods.

The three names submitted and approved by Chang'e-4, namely, Zhinu, Hegu and Tianjin, are also related to the mythological story of the Cowherd and the Weaver Girl.

Image of geographical entity naming in the Chang'e-4 landing area (Source: China Lunar Exploration Project)

With the rapid improvement of human astronomical observation and deep space exploration capabilities, it is inevitable that naming with mythological stories is not enough, so the scope of reference has begun to expand to include various outstanding figures, such as Chinese physicists Yang Zhenning and Li Zhengdao, mathematician Chen Jingrun and hybrid rice expert Yuan Longping, who have also become the names of asteroids. Countries are competing to have their own place names go to space. For example, on April 7 this year, Ukraine's application for Druzhba was approved, and this Ukrainian village name has become the name of a 1.9-kilometer-diameter impact crater on Mars.

Of course, there are many asteroids and landforms named after important people who have worked in aerospace. For example, the asteroid 25143 Itokawa explored by Japan's Hayabusa probe was named Itokawa to commemorate Hideo Itokawa, the father of Japanese rockets. He developed the Hayabusa fighter during World War II and started with a small "pencil rocket" after the war, laying the foundation for Japan's solid launch vehicle technology.

China named the asteroid 3763 after Qian Xuesen, and there is a crater on the moon named after his teacher, Von Karman, and a crater named after a key figure in the U.S. manned lunar landing. At the same time, there are craters on the moon and Mars named after Soviet space expert Sergei Korolev, in order to commemorate his important contribution to the development of the Soviet space industry.

Today, the International Astronomical Union also allows the use of numbers in the thousands to name particularly important people and organizations. For example, the International Astronomical Union is asteroid 5000, and the United Nations is asteroid 6000. (Author: Zhang Xuesong)