Research found that Antarctica Dome A is currently the best optical astronomical observatory site on the ground

[ Instrument Network Instrument Research and Development ] On July 30, the international journal "Nature" published an important result of the research team of Shang Zhaohui of the National Astronomical Observatory of the Chinese Academy of Sciences. Relying on the self-developed equipment installed at the Kunlun Station in China's Antarctica, the research team measured and obtained the atmospheric seeing at night, which proved that the optical astronomical observation conditions in Dome A, where the Kunlun Station is located, are better than any other known ground sites. This research result confirmed that Kunlun Station has precious astronomical observatory site resources, and laid the foundation for my country's further development of Antarctic astronomy research.

Seeing refers to the degree of blurring caused by atmospheric jitter on the telescope's star image. Under the condition of good seeing (small value), the jitter caused by atmospheric turbulence in observing stars is relatively small, so the star images in the photos are sharper and clearer, and the observation of faint celestial bodies is more efficient. In an observatory with excellent visibility, the observation capability of a small-aperture telescope is comparable to that of large telescopes elsewhere. Therefore, the location of the observatory is very important, and seeing is one of the most important parameters.

The geographical and atmospheric conditions of the Antarctic Dome A area where the Kunlun Station is located indicate that the atmospheric turbulence is mainly in the boundary layer near the surface, and the free atmosphere above the boundary layer is very stable. Theoretically, it is expected to have a good seeing. This result is the first time to use the measured data to carry out quantitative scientific statistics and evaluation of the seeing degree of Dome A, and further prove that the atmospheric boundary layer of Dome A is very low, which is conducive to future observatory construction and cost control. .

The research team independently developed the Kunlun Seening Telescope KL-DIMM, participated in China’s 35th Antarctic scientific expedition in November 2018, went to Kunlun Station inland, and immediately put it into observation after successful on-site installation and commissioning in January 2019. The unattended overwintering and long-term fully automatic operation have acquired precious night-time seeing-sight measurement data. The data shows that the median value of free atmospheric seeing is only 0.31 arcseconds, and at a height of 8 meters from the ground, there is 31% of the time to obtain free atmospheric seeing; at a height of 14 meters from the ground, nearly half The time to obtain free atmospheric seeing. In comparison, the median height of the boundary layer of Dome C, which is also in Antarctica, is 30 meters, which is more difficult to obtain free atmospheric seeing than Dome A. Astronomical observation requires extremely high imaging quality. At present, telescopes in the world are concentrated on excellent sites in Hawaii and northern Chile, and the seeing degree is generally 0.6-0.8 arcseconds. The astronomical observation conditions of Dome A are significantly better than the above two regions, and it is expected to become an excellent ground-based observatory.

Kunlun Station is located in Dome A, Antarctica at an altitude of 4093 meters. The Chinese Antarctic expedition team organized by the State Oceanic Administration first arrived in this area in 2005, and it was also a country that reached this area from land. Since participating in the inland scientific expedition at Kunlun Station in Antarctica in 2007, the Chinese astronomy community has obtained a series of astronomical observations and site survey results. The winter temperature at Kunlun Station can be as low as minus 80 degrees. The equipment operating here has to face multiple challenges such as low temperature, frost and snow, limited energy and communications. Based on many years of experience in Antarctic astronomy, the research team has overcome many difficulties and successfully developed the KL-DIMM, a seeing telescope adapted to operate at extremely low temperatures, and conducted field tests and comparisons at the Muztag Observatory of Xinjiang Observatory in the Pamirs. , Confirm the performance of the instrument. KL-DIMM and other equipment were installed in Ice Dome A along with the 35th Antarctic Scientific Expedition (2018/2019), successfully running through the winter automatically. During the installation process, the inland scientific expedition team overcame various difficulties such as high altitude hypoxia and low temperature, and maintained and updated PLATO-A, a facility that provides energy and communication for astronomical equipment.

This work is based on the data of KL-DIMM, completed in collaboration with Australian and Canadian scientists. This research paper includes a total of 9 authors, and participating units include the National Astronomical Observatory, Tianjin Normal University, China Polar Research Center, University of New South Wales (UNSW) in Australia and University of British Columbia (UBC) in Canada. The development of Antarctic astronomy has been strongly supported by the Polar Survey Office of the State Oceanic Administration under the Ministry of Natural Resources and the China Polar Research Center.