At 20:20 Beijing time on December 25, the James Webb Space Telescope was launched and successfully entered orbit. What astronomical observations will the successor to the Hubble Space Telescope make? Is there a similar telescope project in China? The Jiefang Daily and Shangguan News reporter interviewed Shi Wei, director of the Shanghai Planetarium's Network Science Popularization Department.
According to reports, the scientific goals of the Webb Space Telescope are exciting and are expected to solve many unsolved mysteries of the universe. The telescope has four main scientific goals, the primary goal is to find the first starlight in the history of the evolution of the universe, to detect the first generation of galaxies and stars. "Many astronomers believe that between 100 million and 200 million years after the Big Bang, the first generation of galaxies and stars were born. Is that right? What is the shape of the 'first ray of starlight'? The Webb Space Telescope promises to tell us the answer. Shi Wei said.
The Ariane 5 rocket carrying the Webb Space Telescope was launched. Xinhua News Agency/Midland
The reason why it can capture nearly 14 billion years old starlight is because of the powerful observation capabilities of the Webb Space Telescope. It has an effective diameter of 6.5 meters, consists of 18 hexagonal concave mirrors, and collects light in an area 7 times that of the Hubble Space Telescope. And unlike the Hubble Space Telescope's visible-light band observations, the Webb Space Telescope is dominated by infrared-band observations, which coincides with the "first rays of starlight" in the universe.
Why do first-generation galaxies and stars emit infrared starlight? This starts with the "cosmological redshift". This phenomenon was discovered by the American astronomer Edwin Hubble, which states that the spectrum of light emitted by galaxies far away from us will move toward the red end, and the reason for this is the Doppler effect of light and the expansion of the universe. The light emitted by first-generation galaxies and stars peaked in the ultraviolet band, but after tens of billions of years of interstellar travel, these stars entered the near-infrared or even mid-infrared band, which could be captured by the Webb Space Telescope.
The Webb Space Telescope is separated from the rocket. Xinhua News Agency/Midland
The webb Space Telescope's other three scientific goals are to study galactic evolution, star evolution and planet formation, and the detection of exoplanet atmospheres and extraterrestrial life. Shi Wei explained that astronomers have different views on the question of how galaxies evolve, and webb's early infrared images of galaxies are expected to provide an authoritative answer to this scientific controversy. Early stars may not have had nuclear fusion yet, appearing in a "protostar" state. Its temperature is relatively low, only 1000-2000 degrees Celsius, which is also suitable for Webb observation. Which planets outside the solar system could have life? This issue of great public concern may provide important clues for Webb. It can detect the spectral lines of the atmosphere of exoplanets, analyze the content of water, carbon dioxide and other components in the atmosphere, and thus find habitable planets and even find signs of extraterrestrial life.
It is understood that infrared astronomy is a very popular field of astronomy in recent years, and many unknown knowledge in the universe can be obtained in the infrared band. However, infrared astronomical observations on Earth are difficult because infrared rays from the universe are absorbed by the Earth's atmosphere and water vapor. There are very few regions in the world that can meet the observation conditions of infrared astronomy, such as the high-altitude dry region of northern Chile.
Deng Licai, a researcher at the National Astronomical Observatory, introduced the results of the site survey of optical/infrared astronomical observatories in the cold lake area of Qinghai. Xinhua News Agency
It is gratifying that the National Astronomical Observatory of the Chinese Academy of Sciences has found an infrared astronomy station site in China. Based on the observation data of the National Astronomical Observatory Deng Licai for 3 consecutive years, the research confirmed that The Seishten Mountain in Cold Lake, Qinghai is an excellent optical/infrared astronomical observation site, and the relevant paper was published in the journal Nature, which attracted the attention of the global astronomical community. Through the monitoring of the ratio of sunny nights, the degree of apparent well-being (atmospheric stability), and the sedimentable water vapor at the Cold Lake Astronomical Observatory site in Qinghai, the research team found that the observation conditions of the Cold Lake Saishten Mountain site were basically the same as those of the international best astronomical observatory sites, the northern region of Chile and the Monakaya Peak in Hawaii. This discovery will provide significant opportunities for future development in the fields of optical/infrared astronomy, planetary science and deep space exploration in China.