FAST's "big eyes" have the potential to "see" dark matter
2024-06-20
Dark matter and dark energy are compared by scientists to "two dark clouds shrouded in the sky of 21st century physics.". Dark matter has both "wall penetration" and "invisibility", which humans not only cannot see with the naked eye, but can even be captured through astronomical telescopes and electromagnetic methods. To explore them, more advanced observation equipment and more precise experimental techniques are needed. The Wide Field Survey Telescope (FAST) project has emerged. Recently, the project launch and implementation plan demonstration meeting for the key technology design verification and development of the fifth generation wide field spectral survey telescope was held in Jiangyin, Jiangsu. Tsinghua University is leading a joint effort with top domestic and international astronomical institutions to deploy the world's first next-generation spectral survey telescope. So, what kind of configuration does MUST have? What are the characteristics compared to other high-performance telescopes at home and abroad? How will it observe dark matter and answer the mystery of dark matter? Industry experts in the "frontier" and "archaeology" of the Milky Way believe that the current discovery of cosmology and future exploration of dark energy and dark matter urgently require the fifth generation wide field spectral survey telescope. Astronomy is a discipline that heavily relies on equipment, and the performance of telescopes largely determines the level of scientific research. The designed FAST optical aperture reaches 6.5 meters and can simultaneously observe the medium to high resolution spectra of at least 20000 celestial bodies, covering a wide spectral range of 0.36-1.0 micrometers. Within ten years, FAST is expected to make significant fundamental and original breakthroughs in cutting-edge fields such as dark energy, dark matter, gravitational wave cosmology, and galaxy formation. During an interview with Science and Technology Daily, Cai Zheng, the project manager and deputy director of the Department of Astronomy at Tsinghua University, introduced that the stellar spectral survey conducted by FAST will help people conduct archaeological research on the "frontier" of the Milky Way, reveal the formation history of stars in the galaxy, and conduct a more detailed "population census" of the local galaxy group. Specifically, the core scientific goal of FAST is to obtain more accurate cosmological models, in order to explore the evolution of dark energy and the essence of dark matter. It will conduct a high redshift large-scale structural cosmological survey to better explore the origin and evolution of dark energy, the era of cosmic inflation, and to explore the mass of neutrinos. Meanwhile, FAST will also utilize galaxy surveys to better characterize the physical correlation between galaxies and dark matter halos, and explore the essence of dark matter through different observation probes. FAST will also conduct unprecedented large-scale galaxy and black hole surveys to help better understand galaxy formation in different environments, the co evolution of galaxies supermassive black holes, and to obtain physical images of the cosmic ecosystem. Cai Zheng said that compared to telescopes built domestically and internationally, MUST has the characteristics of large aperture, large field of view, high spectral resolution, and high efficiency in dark matter research. As the fifth generation spectral survey telescope, it can simultaneously observe more celestial bodies, improve observation efficiency and scientific output. After the completion of FAST, it will become the last unfinished puzzle for medium-sized ground-based telescopes. Compared to the world's highest performing telescopes, its comprehensive sky survey capability will be increased by more than 10 times, and it is expected to achieve world-class results Cai Zheng said. The optical system that characterizes the dynamic universe MUST in a new dimension has superior imaging quality, like bright "big eyes" detecting deep space. How will it work? MUST project scientist Huang Song introduced that MUST will conduct large-scale galaxy and quasar redshift surveys to measure the spectra of high redshift galaxies in the universe for the first time at the cosmological scale, and obtain the three-dimensional structure of the early universe. In addition, it will also carry out small-scale and flexible spectral surveys to obtain more accurate physical correlation models of galaxy dark matter halos, improve the limitations of small-scale structures in neighboring universes on the essence of dark matter, provide high-precision redshift data support for supernova cosmology and gravitational lensing cosmology, explore new cosmological limiting methods including local velocity surveys, and better achieve the mission of the fifth generation cosmological spectral survey telescope. The high-performance FAST will also support richer and more flexible scientific explorations, such as promoting observational research on galaxy formation and evolution, and constructing more accurate models of the structure and evolution of the Milky Way. In addition, it can also assist time-domain astronomy, opening up a new observation parameter space of spectral time-domain, and discovering unknown new physical fields. MUST is a large-scale scientific device and platform that meets the strategic needs of national basic science development, meets the requirements of the fifth generation cosmological spectral survey, is expected to produce breakthrough results in a series of major key scientific issues, and can systematically and continuously carry out strategic, forward-looking, and comprehensive research. It will strive to carry out the first large-scale time-domain spectral survey. This can not only depict the dynamic universe in a new dimension, but also enhance the synergy with other forms of deep space exploration projects Introduction by Guo Liquan, the person in charge of mechanical systems for the FAST project. The reporter learned that the reason why MUST was able to effectively carry out the fifth stage of cosmological spectral surveys is because researchers have overcome a series of key technical difficulties. Guo Liquan introduced that researchers have solved the contradiction between wide band coverage, high energy utilization, and medium to high spectral resolution by designing a multi-channel spectrometer. At the same time, a color divider is used to divide the band into multiple channels, and each channel is independently designed with dispersion elements, spectral imaging, and photodetectors. The dispersion element is planned to use the latest transmission grating or ion beam etching grating, and be customized according to the shining wavelength and spectral resolution requirements of each channel, in order to achieve the highest grating diffraction efficiency in a compact spatial structure. The overall integrated design of the project has solved the problem of system installation and testing in high-altitude areas. "Expected to achieve first light by 2030." Huang Lei, Director of the Institute of Laser and Photon Technology in the Department of Precision Instruments at Tsinghua University and Chief Engineer of the MUST project, said, "We look forward to significant progress in cosmological research and observation of dark matter and dark energy." Huang Lei analyzed that MUST has both multi-target spectroscopy and imaging spectroscopy functions, and is the world's largest spectral survey telescope. Its powerful spectral acquisition ability will have a profound impact on fundamental cosmological parameters, the primordial inflation of the universe, the essence of dark matter, dark energy evolution, time-domain astronomy (such as gravitational wave electromagnetic counterparts), galaxy formation, exoplanets, and extraterrestrial life. These scientific problems are major issues in astronomy and physics at present, and they are also problems that the international astronomical community is striving to solve first, and may be solved in the next 10-20 years. In addition, the spectral measurement of the apparent velocity of stars in the Milky Way galaxy through FAST can improve the measurement accuracy of the distribution of dark matter in the local universe, and also help to better understand the physical phenomena produced by dark matter at small scales. Specifically, the silver disk stellar survey conducted through FAST can provide high-precision measurements of the density and velocity distribution of dark matter in the Milky Way near the solar system. Meanwhile, the visual velocity survey of a large number of silver halo stars located at the boundary of the Milky Way can further assist in measuring the shape of the Milky Way's silver halo and provide more accurate limits on the total dark matter halo mass of the Milky Way. Huang Lei stated that considering the flexibility and persistence of the FAST spectral survey, it has the potential to become a powerful "dark matter observatory", obtaining massive data related to dark matter. Together with other types of dark matter experiments and observations, it will make important contributions to answering the question of "what exactly is dark matter" in the next 20 years. (Lai Xin She)
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