A three-dimensional map of the Milky Way using classical Cepheid variable stars
Cepheids help to map the Galaxy Cepheid variable stars pulsate, which allows their distances to be determined from the periodic variations in brightness. Skowron et al. constructed a catalog of thousands of Cepheids covering a large fraction of the Milky Way. They combined optical and infrared data to determine the stars' pulsation periods and mapped the distribution of Cepheids and the associated young stellar populations across the Galaxy. Their three-dimensional map demonstrates the warping of the Milky Way's disc. A simple model of star formation in the spiral arms reproduced the positions and ages of the Cepheid population. Science, this issue p. 478 Mapping the Milky Way in three dimensions using Cepheid variable stars shows the Galaxy’s warped disk. The Milky Way is a barred spiral galaxy, with physical properties inferred from various tracers informed by the extrapolation of structures seen in other galaxies. However, the distances of these tracers are measured indirectly and are model-dependent. We constructed a map of the Milky Way in three dimensions, based on the positions and distances of thousands of classical Cepheid variable stars. This map shows the structure of our Galaxy’s young stellar population and allows us to constrain the warped shape of the Milky Way’s disk. A simple model of star formation in the spiral arms reproduces the observed distribution of Cepheids.