LAMOST Telescope, National Astronomical Observatories, China

Mapping the Milky Way and Beyond

Wasatch Photonics volume phase holographic (VPH) gratings are used in telescopes around the world. In this series on astronomical spectrographs, we explore some of the telescopes and instruments in which our gratings are used, and the science they are studying.

LAMOST-Telescope-LRS

>> The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) was designed to conduct a 5-year spectroscopic survey of 10 million Milky Way stars, as well as millions of galaxies. It is a quasi-meridian reflecting Schmidt telescope located in Xinglong Station of the National Astronomical Observatories in China. It uses two arrays of 1.1 m hexagonal plane sub-mirrors, tracking the motion of celestial objects. The light collected is light of individual objects is fed by up to 4000 optical fibers into 16 low-resolution spectrographs, making it capable of capturing up to tens of thousands of spectra per night.

Each spectrograph accommodates 250 fibers, and uses Wasatch Photonics VPH gratings (VPHGs) to cover 370-900 nm at a spectral resolution of 1000-10,000, depending on the grating in use, camera position, and slit width. The blue channel of the spectrograph is optimized for 370-590 nm, and the red channel for 570-900 nm, with low- and medium-dispersion option VPHGs for each. Peak grating efficiency for the low-resolution gratings is approximately 90%, with overall spectrograph throughput of better than 30%.

The LAMOST spectrographs are being used to study the formation and evolution of galaxies by studying our own galaxy, the Milky Way, in detail. The project leading this effort, the LAMOST Experiment for Galactic Understanding and Exploration (LEGUE) studies the structure of its galactic halo and disk components, using the revealed structure to improve models of star and galaxy formation and map the distribution of dark matter, among other things.

Using LAMOST, astronomers have discovered the most lithium-rich giant in the galaxy. The telescope has also reached further to study the kinematics and stellar population of the Andromeda Galaxy.

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