CAS National Observatory, in collaboration with Max-Planck-Institute for Astronomy, has

for the first time calculated the mass of the Milky Way to be 1011M?, indicating a slimmer

Milky Way. Researchers selected some 2500 Blue Horizontal-Branch (BHB) halo stars

drawn from SDSS-II dataset, the largest in number and widest in distribution (5-60 kpc).

BHBs can be measured in an accurate manner, as they are mostly in an evolutionary stage

to become a star, desirable for studying the Milky Way's halo. Chinese and German

scientists have worked out the latest mass of the Milky Way based on kinematics of BHBs.

The finding, with XUE Xiang-Xiang of the CAS National Observatory as the first author, was

published in the recent issue of Astrophysical Journal.

With a large array of halo stars, one can calculate the mass of the Milky Way in an accurate

manner, and study the structure of the Milky Way's halo, in an attempt to understand the

forming process of the system. China's LAMOST that will soon be put into operation is able

to produce the most spectrums in the world, and is expected to work out start spectrums

with an improved quality. A high quality spectrum is very useful for raising the speed of star

viewing and accuracy of atmospheric parameters, making collecting more and better halo

samples possible. China's LAMOST can also be employed to study the structure and

formation of the Milky Way.