Parameters of the spiral structure of the galaxy from data on open star clusters

We use data on open star clusters (OSCs) from the Homogeneous Catalog of OSC Parameters to determine some of the parameters of the spiral structure of our Galaxy: the pitch angle of the spiral arms $$i = 21\mathop .\limits^ \circ 5$$ , the pattern speed Ωp = 20.4 ± 2.5 km s−1 kpc−1, and the initial phase of the spiral θ 0 = 206°. The spiral pattern of the Galaxy proves to have been virtually unchanged over the last billion years, and signatures of the concentration of objects toward the spiral arms can be traced back to this age. However, the number of spiral arms in the structure cannot be determined from OSCs.