Academician Chen Jiansheng: Decoding the Universe: The Golden Age of Space Surveys is Coming

Editor's note: General Secretary Xi Jinping pointed out that "popularizing science is an important basic work for achieving innovative development." In order to help high-level scientific and technological self-reliance, the Science Popularization Department of the China Association for Science and Technology and Guangming Online jointly launched the "Academician High-end Science Popularization" column, inviting academicians from various fields to give authoritative answers to current hot scientific and technological issues in my country, serving to guide more scientific and technological workers to improve their scientific research and popularization capabilities, promote the improvement of the scientific literacy of the whole people, and contribute to the popularization of science for the construction of a strong country in science and technology. #千万IP创科普

The China Space Station Survey Telescope (CSST) is a large space astronomical telescope with a 2-meter aperture. It has a large field of view, multi-band and high-quality image performance, and has the ability to be repaired and upgraded on orbit. CSST focuses on large-scale astronomical surveys and is expected to make major scientific discoveries in multiple astrophysical fields such as cosmology, galaxies, the Milky Way, stars and planets. The tens of PB of data it generates will also bring challenges and opportunities to the interdisciplinary field of astronomical computing. We will usher in the golden age of space surveys.

Space telescopes have observation advantages that ground telescopes cannot match, and are very suitable for astronomical research. The Hubble Space Telescope in the United States is a general-purpose telescope, while the Chinese Space Station Telescope is a survey telescope. So why does my country want to develop a space survey telescope?

Astronomical observations can be divided into two categories: general survey and precision measurement, which complement each other. Sky survey is a general survey of celestial bodies in the universe. Before the 1970s, the focus of astronomy was on precision measurement of stellar physics, mainly using 4-5 meter-class optical telescopes to conduct spectral observations of celestial bodies. In the second half of the 20th century, the strategic direction of astronomical research began to shift. Major discoveries such as quasars, cosmic microwave background radiation, large-scale structure of the universe, dark matter and dark energy have put forward scientific needs for sky survey observations.

On the other hand, revolutionary technological advances in recent decades, such as detectors, big data, high-speed networks, high-speed computer technology, optical fiber technology, computer simulation technology, and space technology, have created conditions for optical sky surveys.

There are currently three major space survey programs in the world: the United States' WFIRST, Europe's EUCLID, and the Chinese Space Station Survey Telescope CSST. Among them, the imaging quality, survey area, number of bands, limiting magnitude, spectrum and other performance of the Chinese Space Survey Telescope are world-class.

I believe that CSST's sky survey data and images should not be locked in an ivory tower for astronomers to study, but should be open to the whole society to allow the public to participate and understand the universe. The public's transition from simply "watching" the universe to "participating" in the study of the universe is the best way to educate the public on the scientific view of the universe, and it can also promote the improvement of the public's scientific literacy.

Now we have entered the golden age of space surveys. Scientists need large samples of astronomical data to study the origin and evolution of the universe. The resolution of CSST in observing the universe is 0.1 arc seconds, which is equivalent to seeing a piece of millet 2 kilometers away. The clarity is 2,000 times higher than that of the naked eye. Its sensitivity can observe stars of magnitude 26 to 27, which is 100 million times more sensitive than the naked eye.

At the same time, the development of computer technology and digitalization have made it easier to process massive amounts of data. In the 1980s, it cost $3,000 to buy 300MB of memory, but today 1TB of memory only costs a few dozen dollars.

According to estimates, CSST will conduct 300 observations per day, generating massive amounts of scientific data and more than 72,000 images to be processed. However, with the help of technological development, storage is no longer a difficult task.

CSST currently has the "right time and right place" and only lacks "right people". It needs tens of thousands of scientists to process massive amounts of scientific data.

As more and more images are observed in multiple colors and at different times in the same field of view, it is necessary to process the images of each exposure of the same field of view at the same time, such as finding asteroids, discovering supernovae, hypervelocity stars, synthesizing color images, etc. However, there are not many astronomers in China at this stage, and people play an irreplaceable and important role in processing scientific data.

Therefore, I call on the whole society to participate in the development of CSST image resources. There are two kinds of rich resources in society: middle school students and social astronomy enthusiasts, which can be fully utilized. For example, American astronomer Milton Humason, who was originally a janitor at the observatory, became Hubble's chief assistant and stargazer through his own efforts. This fully proves that social astronomy enthusiasts are also "crouching tigers, hidden dragons".

In fact, public participation in astronomical research is nothing new. The "Gravitational Lens Search Citizen Science Project" planned and implemented by the National Astronomical Data Center based on real astronomical science data has officially started, and middle school students and astronomy enthusiasts can participate. Internationally, the Galaxy Zoo citizen science project has also been ongoing and has made many interesting scientific discoveries.

CSST has two parts of work, one part requires profound knowledge, and the other part relies on the human eye to discover many valuable celestial bodies. The massive astronomical images obtained by CSST are a huge scientific treasure house. The role of human eyes in observing astronomical images cannot be replaced by computer image processing. Mobilizing the whole society to participate in the development of CSST image resources is a great project to carry out the cosmological education of the whole society.

In order to encourage the public to actively participate, I think the public's discoveries can also be published in books and papers. Under the current conditions, we can prepare dedicated interactive visual astronomy image processing software to automatically generate unified format results reporting reports, conduct training online tutorials, and hold a results exchange meeting every year.

I hope this work can be gradually advanced. If it is done, it will improve the scientific literacy of the entire population. This is a great scientific project, a great science popularization project, and a great talent project that will take at least 10 years.

(Author: Chen Jiansheng is an academician of the Chinese Academy of Sciences, interviewed and compiled by Gao Yali)