Shulou(Shulou.com)11/24 Report--

The Andromeda galaxy (from the University of Science and Technology of China) shows ten thousand stars in the dark at night, and a wisp of cloud begins to be seen in the mirror.

Qi's dream-like layers of blue-purple dust clouds emit a soft, hazy purplish white. this is a fresh picture of the Andromeda galaxy, taken in the first light of the Mozi Survey Telescope (WFST), which was launched on September 17, 2023.

Mozi Survey Telescope (WFST) is the most powerful optical time domain survey equipment in the Northern Hemisphere jointly built by University of Science and Technology of China (USTC) and Zijinshan Observatory (PMO). It is quietly located on Mount Saishten in Lenghu Town, Haixi Mongolian and Tibetan Autonomous Prefecture, Qinghai Province, which is a world-class site with high altitude, low water vapor, low light pollution and sparse vegetation. Here, we can follow the direction of the camera, step into the stars, walk all the way into the Milky way, and observe the universe.

What kind of telescope is this? The strongest in the northern hemisphere!

Mozi Sky Survey Telescope is an optical imaging telescope with large field of view, high resolution and wide band. it is the best time domain survey telescope in the northern hemisphere at present. It can survey the northern hemisphere every three nights and work rhythmically through six working bands u, g, r, I, z, w (320-960nm) to get more detailed and diverse information. Mozi Survey Telescope has a main mirror with a diameter of 2.5m, a 0.73 gigapixel CCD camera on the main focal plane, and is equipped with primary mirror active optical correction technology and excellent main focal optical system to achieve low image field distortion and uniform high image quality in the field of view, so that the spatial resolution can reach 1 arc second, thus the image can be captured in the field of view of 6.5 degrees, and the celestial bodies with magnitude less than 25mag can be imaged.

The night falls, the stars sprinkle into the boundless sky, and the Milky way, like ink marks on paper, writes the pace of light over Mount Sashten. In the twilight ups and downs, the dome of the Mozi Survey Telescope rotates in the direction of the Milky way, making indiscriminate scanning observations, recording hundreds of images of the starry sky and having a wordless space-time dialogue with the vast universe.

What can Mozi's Survey Telescope (from the WFST website) see? Starry photographer ~

When the earth changes with the seasons over time, changes are taking place everywhere in the universe.

The main task of Mozi Survey Telescope is to go deep into the universe to search for and monitor various astronomical dynamic events instead of our eyes, and to carry out time-domain astronomical research. The changes of these celestial bodies over time contain important and unknown information about the structure and properties of the change sources. Some changes require higher limits of the weak magnitude of the telescope, which requires a new generation of telescopes such as the Mozi Survey Telescope to observe. It is expected to observe such as thousand novae (electromagnetic emitters associated with the merging of neutron stars), high redshift supernovae and other transients used in cosmology and multi-messenger astronomy.

The Mozi Survey Telescope also tracks celestial bodies in the solar system to learn more about the solar system, and pays special attention to planets or moons inside and outside the Kuiper belt. In deep space exploration, it can measure celestial bodies with magnitude less than 25 mag with high precision, so it can depict the Milky way and nearby cosmic space in more detail, and let us know about extragalactic galaxies, galaxy clusters and so on. In addition, the Mozi Survey Telescope, as the best survey telescope in the Northern Hemisphere, can complement the Southern Hemisphere Survey Telescope LSST.

How does the Mozi Survey Telescope (from the WFST website) observe? Determined by the observation demand ~

According to the requirements of different scientific objectives, Mozi Survey Telescope has two measurement modes, namely wide field of view survey (WFS) and deep high rhythm survey (DHS). These two observation modes will take up 90% of the observation time over the next six years.

With its reasonable rhythm and time span, WFS model is suitable for the general purpose of time-domain research (such as transient classification, variability statistics and time-domain cosmology). In WFS mode, WFST will scan the northern sky in four optical bands (u, g, r and I), covering an area of about 8000 square degrees. Under good atmospheric conditions, these four bands can reach the depths of 22.27,23.32,22.84 and 22.31mag (AB magnitude) in a single exposure of 30s, respectively, so that a large number of transients in the low redshift universe can be detected, and the variability of galactic and extragalactic objects can be studied systematically.

Mozi Survey Telescope has excellent imaging performance in u-band, and another observation mode, DHS, is mainly aimed at the deep and high-rhythm mode in u-band. DHS will regularly monitor the 2x360 °2 sky area around the equator every year, and will rhythmically combine the information of other bands. The 90-second exposure in DHS mode can reach the depth of 23 mag in u band and 24 mag in g band. The DHS mode can detect energy transients with high sensitivity requirements, and can track transients immediately after the transients occur, such as electromagnetic counterparts of gravitational wave events, early supernovae, fast blue / superbright transients, tidal destruction events, thousand novae, etc.

In the last year, the superposition of the images shows that the WFS mode can reach about 25.8 mag,DHS and about 27.3 mag in the g-band, which plays an important role in exploring the Milky way and extragalactic galaxies.

The Mozi Survey Telescope will combine China's next-generation space missions such as EP and CSST to achieve a combination of land-based and space-based telescopes to obtain a variety of fast transient real-time spectral energy distributions with expected synchronization and synergy.

The action of exploration will always move forward!

Mozi was the first person in the world to record keyhole imaging, and explained the phenomenon of keyhole imaging. The Mozi Survey Telescope is an optical imaging telescope, which is not only a tribute through time and space, but also a kind of inheritance. The ancients saw the sky with the naked eye, but we built better "eyes" to explore the same sky thousands of years later.

The high performance of Mozi Survey Telescope combined with the top site conditions is expected to play an important role in time-domain astronomy, deep space exploration, cosmology and other astronomical fields. When technology falls to the ground and becomes a reality, a starry sky seems to outline the light of science and technology and dreams shared by human beings. let's look forward to new discoveries and breakthroughs in astronomy brought about by the Mozi Survey Telescope.

references

[1] https://wfst.ustc.edu.cn/

[2] WFST Collaboration; arXiv:2306.07590 "Sciences for The 2.5-meter Wide Field S-urvey Telescope (WFST)"

[3] Deng, L., Yang, F., Chen, X. Et al. Lenghu on the Tibetan Plateau as an astronomical observing site. Nature 596,353-356 (2021). Https://doi.org/10.1038/s41586-021-03711-z

This article comes from the official account of Wechat: stone Science Popularization Studio (ID:Dr__Stone), by Chen Bingjie

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