The EAST telescope project: Building one of the largest general-purpose optical telescopes in Asia

Astronomy is an observation-driven science that utilizes telescopes to obtain information from the universe in order to study the most fundamental scientific questions in the universe. The aperture of the telescope determines the number of photons received per second and, therefore, the sensitivity and angular resolution of the telescope so people can see farther, and it is possible to see fainter objects in the deep universe with a larger-aperture telescope.

At present, there are 19 optical astronomical telescopes in the world whose apertures are larger than 6 m, and 14 of them are in the 8- to 10-m class with a maximum aperture of about 10 m, including two Keck telescopes and the Hobby-Eberly Telescope in the United States, the Gran Telescopio Canarias in Europe, and Southern African Large Telescope in South Africa. Most of these telescopes are general-purpose optical telescopes. These telescopes are mainly owned by the United States, Europe, and Japan and are installed in America, Europe, and Africa, while Asia still does not have a single big telescope so far.

In China, the largest optical astronomical telescope at present is the Guo Shoujing Telescope (the Large Sky Area Multi-Object Fiber Spectroscopic Telescope)1,2 with an effective aperture of 4 m, but it is a specialized telescope used only for spectroscopic surveys. The largest-aperture general-purpose optical telescopes in China are the 2.16-m telescope in Xinglong,3 Hebei Province, built in 1989, and the 2.4-m telescope in Lijiang,4 Yunnan Province, built in 2008. China has lagged far behind many other countries in the world regarding optical telescope size, so the construction of an ∼6- 8-m-aperture general-purpose optical telescope is critically urgent.

In 2022, astronomers and engineers from Peking University, National Astronomical Observatories of Chinese Academy of Sciences, Nanjing Institute for Astronomical Optics and Technology (NIAOT) and other institutes in China proposed to build an expandable-aperture segmented telescope (EAST) in China, with an aperture of ∼6–8 m. After completion, the EAST will become one of the largest-aperture general-purpose astronomical optical telescopes in Asia, which will not only provide Chinese astronomers with multi-purpose optical astronomical observation tools but also bring new opportunities for China to carry out international astronomy collaborations.